Nitric Acid from Air and Water

[bongincarnate]

http://species8472.dyndns.org/no2/no2.html



Something called a Birkeland-Eyde reactor, anyone know if something like this would work? Several folks over at sciencemadness.org were discussing this, and it was too damn cool looking to not share.

[FUTI]

I'm trying to reply second time and as newbie I don't know if it is first one pass trough (by what I think it didn't; my computer just freezes itself and that was it). Original old proces of that kind was named by Lavoisier...it is abandoned because it cost too much and only Holland could make it easy that way because they had hydroelectric plants on their dams. After Haber-Bosch process invention it became obsolete...but the name of the reactor you stated is unknown to me (I will google it, and do some research...). Mine first assumption is that it is some new-wave project of the continuous-constant-flow-small-scale-reactor type. Can be interesting but I doubt you guys can have some practical use of it. As for this electrolysis thing I think only ozone producer kind of reactor have some future. What you found is very educative simple mind trilling exercise:)
I did google it and its the same stuff I described.

[Marvin]

bong, SEARCH THE FORUM FIRST!

I suspect neither this thread nor your questionable self will last long enough for my reply to be even read, but there is a massive thread on this subject allready.

http://www.roguesci.org/theforum/showthread.php?t=1919

Birkland-Eyde was the process norway used, it is extremely well known.

FUTI,
I dont know why you brought the headless chemist into this, but the process was discovered by Cavandish, not Lavoisier.

[FUTI]

I will try to find and quote a source of the info about inventor but it can also be a common rivalistic nationalistic idea that no nation is immune at...as example we can quote a diferent Russian and American naming of some chemical elements (because each of them claim priority of discovery). Cavendish or Lavoisier really makes no difference since they are counterparts by the way I see it (both of them are phlogistonic chemist). I stated this only to state a time frame as old process (Layden , but I agree I mised to state this with a necesary reserve about matter. I did in the first post that never saw a light of day...second post was writen in a more hasty manner. And here goes mine browser goes that thing again:(

(If this was the post that vanished into 'electronic fog' then you'd be wrong. It just needs to be approved by a moderator - kingspaz)

[10fingers]

Awhile back I tried the electric spark method of making nitric and it did work. It takes a long time and a lot of electricity. If your system is well designed though it requires little attention and no raw materials except electricity, air and water. My system had numerous flaws though. I have since been rethinking how to do it better and I am going to start working on it. The first system used a neon sign transformer which was rated at only 300 watts. I ran two pieces of copper tubing into a sealed pyrex vessel and pumped air in and out of the vessel with an aquarium pump. The tubing was also the electrodes and the ends of which were held about 1 inch apart. When the air was pumped in it had to pass directly through the arc to go in and out of the vessel.
The flaws in this system I think were that the power output was too low and that the arc should really be as large and wide as possible. Also, the air needs to pass quickly through the arc so that it cools before the NO can decompose.
This time I'm going to use an MOT for the power supply, rated at 1.5 kilowatt. One of the electrodes is going to be attached to a small motor. This electrode will rotate in the center of a piece of steel pipe. The pipe will be the other electrode. As the electrode spins it will make a disc of plasma inside the pipe which the air will pass through.
One problem though is cooling the electrodes. The pipe will be self cooling but the center electrode that spins will be a problem. I might try using a heavy piece of copper with a piece of tungsten brazed to the end.
Another problem is that of starting the arc. I have found that an MOT will only arc a couple of mm's. Once the arc is started you can pull a much larger arc but this is of no help when the electrodes are inaccessible. I might try using a auto ignition coil to start the arc.

[Marvin]

If you use an ignition coil you risk damaging the insulation on the MOT windings.

The electronic solution isnt much good either, you could have a diode on the MOT that protects it, but it would need to be rated for the peak reverse voltage of the ignition coil and the peak current of the MOT.

You could try playing with starter electrodes that take the full MOT voltage over 1mm or so and try to arange is so it gets pulled into a larger arc but with only 2kv or so this might not be possible.

Another possible solution if your arc chamber is strong enough, would be to suck most of the air out and start the arc that way. Tricky to design for particually if you have a spinning electrode.

[10fingers]

Yea, that's what I was going to try is putting a diode in the circuit to keep the ignition coil voltage from going through the MOT. I have some high current, high PIV diodes that I salvaged.
The ignition coil is going to be continously pulsed because when you start blowing air through the arc I think it will want to keep blowing itself out.
Another thing I might try is to get hold of a large toroid and make a high frequency step up transformer. I could make a spark gap oscillator on the secondary of the MOT and put a high frequency, high voltage into the primary of the toroid, then take the output of the toroid and use it for my arc. The spark gap may also provide a means of controlling the current through the MOT so it doesn't overheat. I like the high frequency but I don't really like a spark gap because it makes a lot of noise and will probably require continual fiddling with.

[Zeitgeist]

Another solution could be a Cockroft-Walton multiplier network with capacitors and diodes

[ProdigyChild]

Using a Cockroft-Walton multiplier is difficult, because the burning arc shorts the caps (not a problem) and some diodes (REALLY a problem). Won't last long, I believe.
Using a series resistors isn't an alternative, because it wastes most energy.

I remember times, when I increased power further and further using high voltage switching transistors and rectified primary voltage (230V). Was never really good.

The best results I ever had where a low frequency high energy pulse system made of a car ignition coil and a darlington high voltage transistor. The idea behind it is: Heat up the air very fast by a spark, the shut off the spark and let the plasma cool down by expansion and diffusion quickly. Then next pulse. I had better yields from this less than 30W (!) system than my best 800W high freq. switching design (melting electrodes all the time).
The frequency I use is about 20Hz, about 10A peak current (primary side of course) through the ignition coil. Power supply 15-30V (doesn't really matter, if you adjust peak current to 10A). Make sure to limit flyback voltage to the maximum the transistor can take. I use a diode that tries to charge a capacitor to flyback voltage. The capacitor is held below 400V by a OP + switching transistor + power resistors thus forcing flyback voltage below 400V, too.
Unfortunately, the pulses seem to confuse a NE555 timer and I had a really bad time until I managed to create a reliable pulse generator using a uA2240 (XR2240). That's a timer + digital divider (:256). The divider reduces the effect of unwanted toggling of the oscillator.

You don't need any moving parts for this, physics does all for you: plasma cooling by explosion/expansion, removing product between the electrodes by hot air moving upwards :)
The only drawback is the annoying sound. It's NOT a silent burning arc at all!

[Chris The Great]

I've got a 4 MOT pack and some bottle caps from my tesla coil, I'll try using these with my sparkgap and see how this works. At least it will be a way to get some nitric acid, I still haven't found a source :(

I'll try to figure out the watts/nitric acid produced ratio, at least to estimate what kind of efficiency you can expect from a similar setup. It will be more than using a smooth arc, as when testing my sparkgaps, a straight arc produces very little NO2, while a arc from putting the cap in parallel makes the smell get strong pretty fast.

I'll hopefully do a test within the next few days.

[Marvin]

I think using caps may turn out to be a massive step backwards.

The accepted method is to ignite the arc and then stretch it to the point it only just stays alight. This should provide a good yeild of NO, though better if you can make it move with magnets. If you use a cap you dump all the power into the arc at its shortest point just as it starts. This may look to be generating more power than transformer alone leaving the arc short, but with a long arc more NO should be produced.

[ProdigyChild]

@Chris: have you tried already?

I've made the following experiment: A mains voltage doubler creates 640V (European 230V) with two 10uF caps in series. This voltage is applied across 2-3mm spark gap. No firing of course from this low voltage. Now a spark gap trigger of 10kV is applied between the electrodes, causing an enormous discharge.
My circuit is buildt in a way, that it automatically triggers every 1/50s or every 1/25s.
The result is is a powerful arc (about 50-100W) more or less directly from the socket :D
2-3mm is quite long for 640V, isn't it?

It fills a 100ml glass with brown gas within 3-5minutes. Not that bad!

To be correct, I should note, that:
a) it is not a normal voltage doubler of 2 caps and 2 diodes, but has two 1.3mH inductances between caps and diodes. Otherwise the diodes are fried from RF oscillation and escpecially capacitor voltage reversal (inevitable L-C-system!).

b) a 150uH inductance was put in series with the spark gap to reduce stress on the caps.

Unfortunately, my triggering circuit has random behaviour (sometimes) concerning firing rate. A bit like a Geiger-counter sometimes....

My conclusion is:
Caps don't spoil NO formation. High current pulses from caps DO produce NOx. After a few seconds, the smell becomes noticable.
On the other way, I observed Marvin's accepted method of using the longest possible arc. But rather than stretching it after ignition, I ignite it by HV-ionisation 50 times a second, dump all energy into about 3mm x 3mm x3mm withing microseconds and then have about 20ms of no current flow.
Pulse current is around 50A I estimate.
So my system is a compromise between 'soft arcs from HV' and capacitor discharge.

If someone wants to judge efficiency from color, I can post a series of photos.

[Marvin]

I have to admit that is a very cunning solution.

I still dont think it will do well though in terms of yeilds. The goal involves heating up air to around 3000C and then freezing in the NO. Going to higher temperatures fails to yeild much more NO because of the rate of cooling problem. I would expect a capacitor discharge to get a tiny volume to a massively high temperature and thus waste a lot of power.

[Pietruszkin]

o jezus..

hno3 from air and water, total non-sense..
this method was good for biig institutions..

greetz..

[Anthony]

Everyone is entitled to an opinion - if they can justify it.

Would you care to elaborate on why you think this method is "non-sense", and totally impractical?

[j_dmillar]

This is going back up the thread a bit to 10fingers' rotating electrode plan. If you want to maintain an arc and then maintain it at a longer length, then why not have the rotor off center?

I assume you are planning to have an offset electrode which rotates about the center of the tube. Thuse the electrode is closest to different parts of the tube at different times, yet the distance from the electrode to the closest part of the tube is constant. Instead of this, place the axis of the rotation offcenter. Then at different points in the rotation the distance to the closest point will be different. Set it so the arc just barely strikes at the closest point, and at the other extreme the arc will be moderately drawn out for a portion of its travel. Not a perfect solution, but better than nothing.

Hmm, was just thinking more about it. Instead of placing it off-center, have a protrusion from the side of the tube at one point. As the electrode passes close to that spot, the arc will ignite and will be "carried", I think, around the pipe as the electrode spins.

You could even set up a T-joint or similar in the pipe, and screw another pipe or a rod in and out as the protusion -- once the arc is struck and stable, move it back so it doesn't tend to 'trap' the arc too much

Honestly I don't know if the idea of the spinning electrode in the pipe is a good idea or not, these are just suggestions about how to make it work well. Good luck.

[10fingers]

This process does work, I had a small system set up awhile back. However it does take a long time and uses a lot of electricity. But H2SO4 and a nitrate cost money too.
I don't think you can get much out of this method with just high voltage, you need to have power into the arc. The Birkland-Eyde reactors used industrially used 10's of Kw's. More power, more heat, more NO.
The best setup I think would be with one or more MOT's powering the arc. The arc should be as wide as possible on an axis perpendicular to the flow of air. You want the air to pass rapidly through the arc so that it is rapidly heated and then cooled.

[ProdigyChild]

Any ideas how to measure concentration of NO2 ?
We need some quantitative data. I observed, that white paper gets light brown from NO2 in a few hours - I use this as a qualitative test to 'measure' performance of the arcs.

[Marvin]

Intensity of the brown gas depends too much on the temperature, as would direct reactions. Making nitric acid and then neutralising would be my first choice. Or even leading the gas into sodium hydroxide until the pH changes. Could be fairly sensitive and repeatable if CO2 is scrubbed out of the gas pre arc. Needs an indicatior NO2 isnt going to affect.

[FUTI]

I guess that we could pass the gas stream which contain nitrogen oxides through a sulfite solution and after that determine amount of sulfite and nitrite in solution through titration or spectrofotometry, and also the amount of sulfate and nitrate combined after subtracting the above mentioned value from whole acid measured through neutralisation as Marvin said. There are number of possible solution for this problem...what are the requirements for a detection you want?

[ProdigyChild]

Requirements?
It should work at low concentration and low total amount: 1mg NO2 in 100ml air or similar.
And: everyone should be able to do it.
Expensive chemicals - no problem, if this improves/eases the test.

Dissolving NOx in water is nasty. I have the impression it does not like to dissolve. So the amount of dissolved gas is a function of my patience rather than NOx concentration ;)

[Pb1]

To measure the amount of NOx formed, put a known mass of copper oxide into the water. This reacts with NOx to form copper (II) nitrate, which is very soluble and can be washed away from the insoluble oxide. If you want your NOx back, simply heat the nitrate.

[FUTI]

hm...I'll work on that. You seem to look a solution that do not involve instruments. I'm curious how you colect gas from generator. Do you have a posibility to measure the volume of gas passed through a generator and after that through a water detection solution (that could help a lot!)?

I thought that simple color of gas is good enough for NO2, but it seems that is not good enough for you (anyway it doesn't measure NO2 corect since NO concentration and pressure/composition change make a mess in system). Then I turned to heat capacity of gas, that could work for NO2, but wont work for NO. IR is to complicated for "home-device". I don't know why you find it difficult to dissolve. Make a split in gas line and pass a small stream through a sintered glass into basic solution of known concentration. Measure the volume of gass passed through it. Titration of a sample for base remained give you a total acid oxides produced. Second sample you add KI and acetic acid, little starch and titrate with tiosulfate (or make some other combination like sulfite and "something else") and after oxidoreduction reaction and titration you can obtain second value. Solve as system of two equation with two variables and you will have NO and NO2 conversion. Maybe even ammonium nitrate in acidified solution can generate enough N2 to measure NO from sample directly. If you look for some "lithmus paper" kind of test that could take some time to develop and verify its detection limit (and range).

Don't take this personaly boys, but I agree with Pietruszkin, this is not a good way to nitric acid from my point of view, but I still look close your work because where is the good chemistry there I'm;) So I understand your work and value your effort, but it is not cost effective, but boy you will be pride to make it:)

I can think several more solution involving electrical measurement in water solution etc., but it needs specific equipment and if you are not sure that gas can be dissolved what is the point of making such device even if it could work continously? BTW I know that there is some kind of strategy to purify exhaust gasses from electric coal plant removing sulfur and nitrogen oxides by some catalytic process and ammonium sulfate is one product (I guess then the N2 is the second)...anyone have an idea how and could this be used here? It would be nice if you could just measure the weight of produced salt.

[Pietruszkin]

Everyone is entitled to an opinion - if they can justify it.

Would you care to elaborate on why you think this method is "non-sense", and totally impractical?

hah
maybe i think so becuse in my country hno3 is as expensive as mineral water? :rolleyes: i don't knowww :D

[Anthony]

Good for you!

So, your suggested alternative method for making HNO3 is to buy it? What about those who cannot buy it easily, or cheaply? What about if one day its sale is restricted by government? What about makiing HNO3 simply as an academic exercise?

Basically, I'm question the worth of your input into this thread. Your first post was an affront to the contributions of other members, and described a real industrial process as "non-sense". Your second post simply boasted about your supply of HNO3.

How has any of this contributed at all to this thread?

[nbk2000]

Braggerts and morons are about as welcome here as a leaky asshole in a crowded subway car after a Texas chile cookoff. :rolleyes:

[ProdigyChild]

@FUTI: I do like electronic sensors, but possibly other members don't. If I want to compare my yield with others, I can't insist on special equipment.
Any known electric effects of O2, N2, NO, NO2 are welcome. O2 does slightly increase magnetic fields (paramagnetic; ur=1 + 1.4E-7), while N2 is diamagnetic (ur=1 - 3E-10).

What about IR properties of NO2? IR diodes and detectors are easily obtainable (wavelength a bit above 800nm I believe).

When experimenting, it's convenient to us a closed glass.

By the way, I had the following idea today: I put the electrodes into an (insulating) oil bath, electrodes sticking out of the surface a few cm. Now I put a glass on top of it and let the arc burn for a few minutes inside. The oil prevents gases from flowing in or out. After cooling I should be able to measure a reduction of gas volume as:

N2 + 2O2 ==> 2NO2 (3 parts ==> 2 parts)

Of course this works only, if there's enough O2 to form NO2 (in favour of NO)

[Pietruszkin]

Good for you!

So, your suggested alternative method for making HNO3 is to buy it? What about those who cannot buy it easily, or cheaply? What about if one day its sale is restricted by government? What about makiing HNO3 simply as an academic exercise?

Basically, I'm question the worth of your input into this thread. Your first post was an affront to the contributions of other members, and described a real industrial process as "non-sense". Your second post simply boasted about your supply of HNO3.

How has any of this contributed at all to this thread?

ok, sorry for my non-sense post (as this method of obtaining hno3 :D :p [joke])

havent you got any connections with chemists or other people who can obtain hno3 very easy? oh people, think sth, ask people..

old chemists could understand your sitiuation..

if u havent got any connections, you can go to the gas station and buy some electrolyte (rare to obtain, but can try) - heat this (this is 30% h2so4), -water is pairing-> and you have ~90% h2so4, add some kno3 and ya can nitrate sth (or destylate this mixture to obtain fume hno3)...

havent got destilation aparature (? [poor english]) - do it!
instead of distilling flask - shampane bottle, some glass pipes etc)...

thats all!
and once more sorry for my previous post, but i cant imagine that i cant receive basic (chemicals) like acids (hno3, h2so4) etc..

greets

ps, i have request - if i write sth bad (grammar) - tell me - i am learning english, but it isnt my speciality) ;)

[Pb1]

I posted this method a few days ago but it never appeared for some reason.

Put a known mass of cupric oxide (CuO) in your vessel with some water. The NOx should react with this to form copper (II) nitrate and leave insoluble cupric oxide, which can be filtered out and weighed. If you want your NOx back, just heat the nitrate.

@Pietruszkin: That method and its variants have already been discussed on this forum ad nauseum. Please search before posting.

[Marvin]

ProdigyChild,
Most oils will react with the NO2. For IR to work you would need specific magic values of IR LED. You could use the brown colour of the NO2 radical but you would need very accuratly controlled temperature at measurement. Sodium hydroxide will remove all the NO2/NO from the gas but at only a few percent NO2 I think experimental error would outweigh the results for most people.

Pb1,
The copper oxide idea is insteresting, but I dont know how fast or well it would react. Also it forms a hydrate that cannot be fully dehydrated by heating (decomposes first). A decent potential method if you can ensure what you have is the pure oxide. I would expect some nitrite to be formed as well from NO2 and NO, but this should not affect the math based on remaining copper oxide. Dehydrating reliably to the same point and weighing accuratly might be more tricky.

[ProdigyChild]

@Pb1 I have to measure the amount of dissolved copper nitrate or is there a way to dissolve CuO or Cu2O only from the insoluable part?
I guess I'll try a pH-based test first.
Measuring NO2 yield seems to be double as difficult as producing it!?

Another question:

When I ran a 25W arc for about 1/2hour, I got a white (!) dust on the walls of the 100ml glass. When dissolved in water, a faint blue colour can be seen.

The electrodes are copper (really pure one - from electric conductors). The heat evaporates some copper.

The only white copper salts I know are CuSO4 and CuCl.
What could that white dust be? A copper nitride? anhydrous copper nitrate?? :confused:

[Pb1]

Yes, I was thinking that you could weigh the oxide left behind. You would first filter out the insoluble part left behind and wash it free of the nitrate. Then you’d heat it to above 160C to drive off water and decompose the hydroxide back to the oxide. The only problem with this is that you might get different oxidation states of the oxide and have to dissolve it in sulfuric acid to get CuSO4 which could be dried out and weighed.

I don’t think nitrites would really be a problem. Nitrous acid would decompose at the surface of the water, leaving only nitric to react. Any nitrite ions lying around would be removed as HNO2.

This idea could also be applied to other elements and their oxides.

[FUTI]

I agree copper oxide idea is interesting, I believe that old Egypt used some copper based procedure for nitric acid so I guess this can actually work maybe even as analytical procedure. Don't take this as certain the info is from history of chemistry book I read once. Now where is that...I need to clean up my room more often:)

[Chris The Great]

[LEFT]
@Chris: have you tried already?

Unfortunatly, technical difficulties have prevented a test. The 4 pack decided to self destruct my 240V circuit breaker, and so I have no high voltage ability right now. The breaker replacement was also low on my priority list, so I haven't had a chance to buy a new one.

I have a two week break coming up, so I'll probably have time to get my parents to pay up :mad: and get a new breaker as well as something to limit the input power to about 7000 watts. I can then build the actual generator after I get some washers and nuts to heatsink the electrodes inside the pipe, where the airflow is. I kinda got pissed after I blew the breaker and didn't do any more work.....

Would one of those black 'misting' hoses used for watering a garden work well for a bubbler, or would the NOx/nitric destroy the material to quickly?

[xyz]

The hose will be eaten away much too quickly, leaving you with no hose and nitric that's contaminated with the reaction products.

[Mr.ANFO]

In Canada HNO3 is unable to be purchased in 50% vol or above unless you are licenced.

[ProdigyChild]

I'm still dreaming of making NO2 that way.
In contrast to most of you, I focused on low power systems, that can run without interruption.

Yesterday I finished a relative simple, reliable HV-system. I uses a car ignition coil and a small circuit, that allows to plug that into the 230V socket. The coild produces an arc of 20-25mm, total power consumption is 9W and nothing gets even warm. It takes 20min to form visible NO2, with the vessel (0.5l) still beeing only slightly warm.

The good thing about this circuit is, that the arc is switched of nearly all the time, only 50times/second it creates a intense pulse of 200us / 650V / 18A primary. This pulse is one full sine wave (5kHz). Three quarters of the energy (1uF cap charged to 650V) seem to be gone afterwards (used by the arc + device losses).
If watched with an oscilloscope, you can see a flat line with a 18A spike every 1/50s.


I've described a powerfull three electrode setup (triggered spark gap) design in this thread before, but I have problems harnessing one problem: the trigger electrode must be thin to be a good trigger electrode. Also it must be close to the main electrodes, to trigger the main current. But then the powerfull main arc eats it away eventually. And the main electrodes need to be MASSIVE otherwise they are aeten away slowly, too. The more massive, the electrodes, the harde to trigger!
Problems, problems, problems.....
...some of which we all share :(

Now comes the good news:
The triggering problem can be solved easily!
Below I attached a schematic. The electrodes doing the real arcing work are gap G1. In the shown configuration, C3 is charged negative, while line P in negative (negative half sine of mains). Likewise C1 is charged at the same time.
A half wave later, P is maximum positive. At that time, switch Q is closed, discharging C1 (mains+charge = 2x 320V) into the ingition coil. Secondary side of the ignition coil charges C2 (290pF / 30kV) to about 10kV until G2 (9mm) breaks down. This in turn switches L2 (1.3mH) to 10kV and the inductance L2 is really willing to allow that, because the spark gap switches so fast. At that moment, you have the 10kV also across the main gap G1. G1 is driven into conduction and C3 will be discharged over gap G1, too, although it was by far not charged to G1's breakdown voltage. C3 can be a huge cap or a MOT capable of driving POWER through G1.

The point is, that the voltage of C3 (or MOT) needs to be in sync with mains voltage. A transformes is in sync, unless you've done some magic. The schematic shows, how a simple capacitor can be used as power supply. Be careful with the polarity of D1 and D2, otherwise, the whole thing will turn into smoke :eek:

I've modified the design described and used a transformer in place of L2. This transformer increases the overvoltage further (2:1) resulting in an even longer arcing across G1. This transformer uses 15 / 37 turns of wire on a 8cm diameter, 15cm long cardboard tube. Limiting factor seems to be the capacitance of the windings. I've not exceeded 1inch spark length so far :(
But come on, this method ignites an arc, that can have 1000Amps, low voltage (<1KV) and massive power. And it re-ignites it every 1/50s if necessary, so you can't blow it out!

The only downside is the need for good timing of the switch. I've done with a SCR + 1 trigger diode (DIAC), 2 resistors, 3 Z-diodes and a 0.1uF cap. Can't be that difficult, does it?

[devoted to 10finger's suggestion about ignition coil triggering, page1 of this thread]

EDIT:
Using a transformator-version and not grounding the circuit properly seems to be a bad idea. 5minutes ago, my setup found its own way to earth ( ;) ) by the help of the pre-ionizing HV and wiped out electricity in my lab. No fuse seems to be gone but still dark!?

But I could test it before. Quite powerful! Nice brown NO2 within minutes!

[ETCS (Ret)]

V. S. Komelkov and V. I. Modzolevskii developed a small apparatus for the purpose of Nitrogen fixation (Nitrogen Oxides) which is described in the Russian Journal of Physical Chemistry 52(6), 1978 "Formation of Nitrogen Oxides in High Current Pulsed Discharges in Air"

The process can be made quite efficient, even on a small scale, and the Nitric Oxides produced can be used for the gaseous phase nitration of dry cellulose directly.

One of the primary applications of the device was intended to be the production of slow release fertilizer (cellulose nitrate) by the use of dried vegetable waste.

http://www.gobrainstorm.net/~ohare/

[ETCS (Ret)]

Prodigy Child,

Your Post above (#37) presents some interesting possiblities.

Your Ignition Coil portion of the circuit is Capacitive Discharge in the style of the automotive ignition systems many electronics experimenters constructed in the 1970s and 1980s for their cars. It is easy to control the timing of the discharge into the primary of the ignition coil with an SCR or HV MosFet and associated timing/trigger circuitry which would operate on about 12 volts DC.

To simplify the concept, I'd recommend pulsing the ignition coil capacitive discharge input at several hundred hertz and applying the ignition coil output to a high voltage capacitor (which can be home made) across the spark gap in order for the arc to pulse operate at 30 KV or more.

Several pulses of ignition coil output would charge the high voltage capacitor, through a suitable high voltage diode, and build its potential stepwise up to the point of spontaneoous arcing across the gap when the energy would be disruptively discharged in an intense "bang" similar to what Tesla did with his infamous Tesla Coils.

By adjusting the width of the spark gap you could adjust the discharge pulse rate to some suitable range in the vicinity of 20 to 50 or more discharges per second.

By the way, what did you use to create your schematic diagram? It is very clear and easy to follow.

[fractional distiller]

It seems to me that even though both of the two threads that are focused around the birkeland-eyde reactor no one has gone through a balanced chemical equation.

I myself am in the process of prep work for construction on my own reactor but I can not do any of the really important calculations without the proper equation for the reaction.

From what I can determine the equation goes such as this.
The 78% diatomic nitrogen in air and the 21% oxygen are pumped into my reaction vessel with a certain surplus of O2 to help the yield of the reaction which saves me some efficiency due to the heat conversion.

N2,O2==> 2N + 2O: plasma breaks air apart and when it cools forms 2N + 2O
2N + 2O==> 2NO2: after cooling it reassembles as 2NO2
2NO + O2==> 2NO2: after exposing the nitric oxide to air yields 2NO2
2NO2 + 2(H2O) ==> 2(HNO3) + H2

Comments, suggestions, corrections, are all welcome. Especially corrections it would suck to figure out all the math for my dream set up and have it catastrophically fail on me.

[Alexires]

Actually, I think that the reaction would look something like this:

N2+O2 ---(heat)--> 2NO
NO+1/2O2 ---(heat)--> NO2
NO2+H2O --> HNO3

I'm assuming it would be something like this because of the Ostwald Process (making nitric from ammonia gas).

I don't think you need to worry much about the ratios, depending on what reactor you make. If you just passed air into a jacobs ladder, then passed the air straight into water, you should have 68% fuming nitric acid, if you wait long enough.

Also have a little look at this (http://www.efma.org/Publications/BAT%202000/Bat02/index.asp). It may help a little.

[NGfan]

Ok, what would be the preferred voltage for this experiment, between 4 and 10 kv, and what would be the rate of air flow throught the arc? I'm going to -attempt- this project but will be pissed if I buy £100 worth of transformer that does nothing...

[megalomania]

I will be trying this experiment too as soon as I can locate a suitable HV transformer.

I think you guys may be reading a bit too much into this project at this time. If you want theoretical kinetic mechanisms and thermodynamic equilibriums perhaps another website, or rather just about every other website, would be more suitable.

What you should be concerned with at this point is if the damn things works, and HOW to actually do it. I will be plinking down some hard coin as well, and I will be disappointed if it does not work, but I am willing to take the risk. That's why it's an EXPERIMENT, not a recipe.

To my knowledge there is no system like this you can buy, no website demonstrating it, and no book with the procedure written down. The Ohare patent is very compelling, and it is what I will be trying to accomplish, but if that guy actually got this thing to work, then how come he can't put a picture of the working apparatus on his website?

NGfan, if you want your question answered, a question I want to know as well, you are just going to have to do the experiment and find out. That's what I intend to do. We are blazing a new path here.

[fractional distiller]

I agree with Mega here definitely this is a new path. There is one website on one of the two threads related to this topic, species I believe is the site, he has pictures and claims to actually have done this with success but right when you get to what really counts the end results and final data there is nothing. So it’s sketchy at best.

Although Mega I am sorry I do not agree with you with the idea of just pure experimentation. Now let me explain why, now if it turns out that I am wrong I am sorry for opening my ignorant mouth. The purposed way I believe to go through this is going to require two fields of knowledge the first chemistry which I believe we all have a little knack for, and the second which I have no idea about electricity. This is going to be a little something like electrochemistry except we do not have an electrolyte and our substance is gases not liquids.

We need to investigate the bond energies required to break down each molecule through its steps in the reaction process; this is why I wanted to see a balanced equation. From here we need to go about doing the dredge work of calculating how much energy it translates to in raw power from electricity. Then the devil is in the details here we have to find that special equilibrium point where we balance volts and amps so that we have enough power to break our bonds and have them reconnect but keep the amps down just enough not to cause problems with thermal decomposition. This is where the experimentation is going to come in.

I purpose someone run a bench test, I myself will try to perform one but in all honesty it probably will not happen. But if it does of course I will share my results.

It’s my hope we can pull together and collaborate what the energy to break down the bonds will be and then convert that to a certain ratio so we can just multiply that ratio to an amount to get a rough estimate. Then we need someone who has the experience and knowledge to help us find the sweet spot for our power input needs.

This is too big of a project for us to handle by ourselves, it would be better as a combined effort. I will try to step up and lead it if I can.

• What our first priority is for someone to post a balanced equation and I mean completely balanced even though its may seem trivial.

• Explain or all of us collaborate how much energy will be needed for the reaction. Again the more superfluities and trivial the better so we can see every aspect.

• Finally try some bench test for what power we need and what amps/volts combination works best. Then extrapolate are design from there.

[megalomania]

I agree that the calculations and equations are important, after all chemistry would not be chemistry without those things. First things first we have to try this and see if the theory bears some semblance of truth. You can learn more from a few experiments than you can with thousands of hours of theory. The opposite is also true, the theory can guide your experiment.

My point here is we have the theory telling us the reaction in general should work, and so it has guided us to this method, but only experimentation will give us the specifics.

I guess I have an advantage because I have already seen the thermodynamic equations of state for this reaction. I glossed over them at the time because they didn't inform me HOW to do the experiment, just that it is possible. I have not saved or bookmarked those files, but they are out there. There is always plenty of theory out there.

Who can tell I loathe physical chemistry, eh? I feel if your not working with chemicals, you are a physicist :)

[NGfan]

Well, I AM going to try the experiment, and post my 'trailblazing' discoveries. I will buy the little extra equiptment I need, and test to see what factors such as; pressure, oxygen content, power, volts and current affect the percentage and also the efficiency. The website www.signbuyer.co.uk has politely informed me of the transformers that will provide for me a jacobs ladder without tripping the trip out switch. (The surplus ones have none, which is slightly scary), and I will buy two to three, to test the difference in relation to voltage and power ect. For all you non-UK scientists, just find Noen sign transformers, and ask the company. Also remember to post results, as nitric acid is the base ingredient of many explosives and a valuable chemical to be made purely from electricity, air and water. Apart from this, I have a life, so the results may be delayed or fragmented.
Note: I know it's mainly nitrogen which the content should be higher, but I can't make that, and -apparently- introducing extra oxygen into the air improves performance.

[fractional distiller]

Mega is right first step is to see if the theory bears any semblance of truth. As of right now what we need is instructions for a makeshift Jacob’s ladder. There are thousands of sites that teach you how to build one but I am not interested in wasting my time figuring that out someone build one and report to the forum with a step by step on this process. That will make it easy for everyone to build a system for bench tests.

After we have the plans that someone has built and tested with not excessively hard materials to get, or that can be done by just following a simple set of instructions that the person posts on the forum. Set it up in a glass container or any container you see fit, personally I will be using a glass. Set up an electrolysis cell for water so you can pump a little excess O2 into the chamber that has our Jacobs ladder in it.

Run it for a while and check to see if any NO2 does appear. After this find your own way to bubble the gas through water. I personally am going to try to use my extra O2 house from the electrolysis cell and pour water in it.

After this just check for nitric acid by simple litmus paper of if you want to get technical you could check its specific gravity or do a titration test with baking soda. It is really your own preference on testing it. After this we just post our results and findings.

• So we need simple (pre-tested) instructions for an inexpensive Jacobs’s ladder that even the most kewl kids can set up. Hey lets face it if they want to try they will most likely die from electrocution from the NST and that would be like killing two birds with one stone getting dirt cheap HNO3 and killing some kewls in the process.

• Pictures and for the love of GOD explain what you are doing just don’t send pictures and say random shit that makes no sense and doesn’t help that just wastes time and my patience.

• Post your work for figuring out how much acid you formed if any at all formed.

[defiant]

"SYNTHETIC NITROGEN PRODUCTS" (Dupont Industries) pgs 215-216 states as follows:

The Birkeland-Eyde or Arc process made nitric acid by 1) passing air through an electric arc, 2) forming nitric oxide, 3) oxidizing NO with air and 4) absorbing the resulting oxides of nitrogen in water. The reactions are shown in Eqs. (9.2) through (9.5):
N2 + 02 —‘ 2N0 (9.2)
2N0 + 02 —* 2N02 (9.3)
2 NO2 + H20 —~ HNO2 + 111403 (9.4)
3HN02 —‘ + 2N0 + (9.5)

The arc is spread into a disc by an electromagnet. The process operated in Norway from 1905 to 1930. It used hydroelectric power, but it was made obsolete by the ammonia oxidation process. This process was first used in the United States in 1917’.

Presumably fllattening discharge by using an electromagnet increases the yield.

That's all the information contained in the above referenced source - but I recall another book that was in the filesharing network that went into greater depth.

Does anyone remember the name of the file?

[chemdesperate]

This sounds like a project I would like to pursue. I have a 15kv15ma NST that I havent used as much as I'd like to. I entended to make a tesla coil a while back but never got around to it.

I would build off of magelomania's idea. If Im not fully giving credit to someone else out there, Im sorry. Please excuse any typos.
This is all theoretical.

I would take a secotion of pvc pipe and cap it on bolth ends. Before hand placeing some sort of efficent plasma produceing device in the pipe. Then tap bolth ends of the pipe to fit electric solinoid sprinkler valves on each ends of the pipe. this way the pipe is a more controled enviroment with sealed electrodes and airtight fittings.

Now I would hook up a compressor to your valve thread which is probly 1/2inch. I would adjust your pressure to 2x or 3x your STD. Or two times your standard atmospheric pressure.

Then on the other end of the pipe, you should connect some sort of flexable non-corosvie pipe to the end of the sprinkler valve. then run that pipe to your bubbler of choice. I was thinking if you were to seal the water and NO2 in some sort of container that could be turned up side down over and over again so that the gas could more throughly pass through the water.


The only real difference is that Im useing electronic valves to seal of your NO2 produceing environment. That way you could get purer NO2 gasses, not loss any of it, and then make a proper timer to open and close the valves and given times for a beter HNO3 produceing cycle.

[defiant]

Found the file, its the "Industrial Nitrogen Compounds And Explosives", Manual of Chemical Technology III. Pages 21-26 are particularly interesting, but the intro and the work as a whole is interesting. http://www.sciencemadness.org/library/books/industrial_nitrogen_compounds_and_explosives.pdf or http://mihd.net/9utyb2

This book also cites sources, including:

- A.W. Crossley, "The Utilisation of Atmospheric Nitrogen" (Thorpe's "Dictionary of Applied Chemistry," Vol. III., p. 698). 1912.

- J. Knox, "The Fixation of Atmospheric Nitrogen." 1914. http://www.sciencemadness.org/library/books/fixation_of_atmospheric_nitrogen.pdf

- Donath and Indra, "Die Oxydation des Ammoniaks zu Saltpetersaure und Saltpetriger Saure." 1913

- Donath and Frenzel, Die Technische Aunutzung des Atmoshpharischen Stickstoff." 1907

- Escard, "Fabrication Electrochemique de l'Acide Nitrigue et des Composes Nitres a l'Aide des Elents de l'Air." Paris, 1909.

- Caro, "Chemical Trade Journal, 1909, 44, 621.

- Haiier and Koenig, "Zeitcsch. Elektrochem." 1910, 16, 17.

- E. Kilburn Scott, "Production of Nitrates from the Air." Journ. Soc. Chem. Ind., 1915, 34, 113.

There may be spelling errors in this list due to legibility issues with the text, nor are foreign punctuation marks included.

[megalomania]

I will be attempting the allegedly improved process of forming nitric oxide by electric arc as explained in US patent 4,877,589. This patent uses a tungsten catalyst on spherical alumina to increase nitrogen fixation and to shield the resulting NOx gasses from the destructive effects of UV light produced by the electric arc.

If his (O’Hare) theory hold out, and I have no reason to doubt this process does work, this catalytic method should give greatly improved yields based on the energy input. I rather like the idea of being able to make nitric acid from little more than air and electricity. Let the fedgov ban that!

I know a tungsten based catalyst is not exactly OTC from what I know of the availability of tungsten compounds now, but I can worry about that after I actually get this thing working. I am sure someone cleverer than I will eventually dig up the chemistry of how to make soluble tungsten compounds from the metal.

I also intend to continue research on my catalytic ammonia burner once I get the design of my improved electric furnace finalized and constructed. I actually found a picture in a book of a bench scale ammonia burner that is very close to what I have already. There is hope there, the process does work. Part and parcel to this experiment is a way to generate enough ammonia to make the process economical. This leads me to my tangential project of making ammonia by the urea-to-ammonia process (U2A), the current industrial wunderkind of onsite ammonia production made possible by boiling urea under slight pressure. Ammonia generation (economical at that) has its own uses beyond nitric acid.

[NGfan]

Well, I'm following the more simple designs shown here: http://species8472.dyndns.org/no2/no2.html and when I achive maximum concentration, either sulfuric-distill, or crank up the pressure and see what conc I can get as it goes up. :p

[defiant]

NGFan: How do you plan on getting sulfuric acid from that setup? I'm not an expert on the subject, but its designed to produce nitrates.

Also, as was pointed out earlier, the link you refer to hasn't been updated in years, and the experimenter hasn't posted results/yields.

Meglomania: You're ahead of me on all of this. I have legal issues and my government protectors watchful eye to contend with right now. Not that there's anything illegal about producing nitrates - I've simply been focusing my attention and financial resources on other toys.

Despite my misplaced priorities, I'm very interested in any experimentation you do with producing nitrates from urea and/or amonia. It's been an interest of mine for some time now, and thus I'm favorably inclined as to the direction of your research. In short order I'll be joining you in experimentation, thus I'd greatly appreciate you keeping me advised.

[c.Tech]

NGFan: How do you plan on getting sulfuric acid from that setup? I'm not an expert on the subject, but its designed to produce nitrates.

He meant when he gets the max concentration for nitric acid (from bubbling NO2 through water) he would distil it with sulfuric acid to get 100% HNO3.

[NGfan]

That is correct, although I don't see why you can't just distill it off the water... I've heard it destroys it. Anyway, buying NSTs tomorrow at 10 kv and 5kv. Also, it doesn't matter he's not updated recently, he still has two different reactors. Does matter about yeild though. I think sciencemadness had something on that.

[fractional distiller]

After a few more searches through every search engine known to man I have found a balanced equation that makes sense.

I already knew this much
N2, O2==> 2N + 2O: plasma breaks air apart and when it cools forms 2N + 2O
2N + 2O==> 2NO2: after cooling it reassembles as 2NO2
2NO + O2==> 2NO2: after exposing the nitric oxide to air yields 2NO2

But what I did not know was what happened when
2NO2 + 2(H2O) ==> ?
Well know I do it is
2NO2 + H2O ==> HNO2 + HNO3
H:2/N:2/O:5 == H:2/N:2/O:5 <== Everything checks!

Now comes a bit of problem we now have nitrous acid (HNO2) in the equation I can not find its boiling point anywhere. We have to find that after using your preferred method with your arc to separate the nitrous acid from our brand new nitric acid! This makes home preparation a lot more complicated then I originally thought. But no matter I do have the glassware to fractionally distill my acid under a vacuum. (I know you can create your own acid with potassium nitrate and sulfuric acid this way, but where is the fun in that, plus this lets me keep my supplies for other uses and in the long run this is significantly cheaper too).

I am on my way to figuring out all necessary equations, I know theory does not get you much of anywhere but I find it interesting! Any and all help would be greatly appreciated Exemplum Gratium ==> Joules of heat, electric circuit design, arc shape & expansion, and any other ideas that would help in the set up for the Jacobs ladder and a way to process it.

[Alexires]

Fractional Distiller - Congratulations on your research. Unfortunately, I don't think that it is that simple. I can't remember where I was reading it, but there was a lot of debate about how HNO3 exists in solution, probably from its changing nitrating and oxidizing capabilities at different concentrations.

I think it is a given that NO2 will form in an arc - Look at lightning. That forms Ozone (O3) and NO2. How much it forms is a different matter. I think that this is probably a case for experimental results. We can hypothosis all we like, but we won't truly know if it is feasable until someone makes a BE reactor.

[ultma]

dont know if this helps much

Varation of Equilibrium Constants with Temperature

values of log K<SUB >p</sub> at variuos temperatures ( <SUP >o</sup>K )

N<SUB >2</sub>(g) + O<SUB >2</sub>(g) <=> 2NO(g)
298<SUP >o</sup>K, K<SUB >p</sub>= -30.4
700<SUP >o</sup>K, K<SUB >p</sub>= -12.3
1100<SUP >o</sup>K, K<SUB >p</sub>= -7.4
1500<SUP >o</sup>K, K<SUB >p</sub>= -5.0
2300<SUP >o</sup>K, K<SUB >p</sub>= -2.8

2NO(g) + O<SUB >2</sub>(g) <=> 2NO<SUB >2</sub>(g)
298<SUP >o</sup>K, K<SUB >p</sub>= 12.3
500<SUP >o</sup>K, K<SUB >p</sub>= 4.2
700<SUP >o</sup>K, K<SUB >p</sub>= 0.7
900<SUP >o</sup>K, K<SUB >p</sub>= -1.3
1100<SUP >o</sup>K, K<SUB >p</sub>= -2.5

[ThimeBom]

Anybody who is having trouble finding a neon light transformer (NST) could possibly use a small flyback transformer from a small television or computer monitor. In TVs or monitors that have very large CRT's they can reach voltages of over 30,000 Volts.

[fractional distiller]

Alexeries and Ultma thank you both for your responses. Alexeries I will go and try to check if what you claim is true, I really hope not. Ultma thank you for you figures can you give a little explanation on what you mean it is a little vague

Well from what I have found Jacob ladders require high voltage at low amps. But what I am finding is higher amps produces bigger arc, where as high voltage determines how close on your vee shaped structure the arc begins.

Can anyone else verify this, if you do, please cite your sources!

Does anyone live in the Maryland area because I would really like to get a group together to work on this! This might seem a little taboo but I think it would be for the greater good of the project if we could get together pull are resources and take pictures, movies and draw up schematics for our designs. Going at this alone is only going to be harder and more challenging where as if we can work together we all may have very cheap nitric acid all to ourselves!

Speaking of citing my sources for the nitrous acid came from Defiant's web sources that he posted, which are down for some reason now!?

Does anyone have any progess on there BE reactor yet?

[megalomania]

Theory may tell you that combining nitrogen dioxide and water and will form nitric acid and nitrous acid, but only actual experimentation will reveal that this is, in fact, wrong.

The reaction is:

3NO2(g) + H2O(l) <==> 2HNO3(aq) + NO(g)

I have written about this reaction before because I encountered it in my earlier research in designing a way to make the nitric acid. The equation is from the Kirk Othmer Encyclopedia of Chemical Technology 4th edition in case you wanted a reference to double check.

I actually had personalized license plates with this reaction, I won’t tell you which part yet. Nobody EVER got it except a few chemistry professors. I even had a cop pull me over and ask “First of all, what does your license plate mean?” I almost put this equation as a bumper sticker to better explain it, but honestly the sheeple would still not understand. I have a new chemistry themed plate now.

This reaction is important to know because it helps to determine the final design of a device to make nitric acid. Just bubbling NO2 into water will result in a loss of 1/3 of your precious NOx gas. Industrially they release NO2 gas into the base of a tower with a water sprayer on top. The water spray then results in a sort of waterfall on the sides of the tower. The volume of NOx gasses diminish the farther up the tower it gets as it encounters more and more water. The water at the base of the tower where the fresh NO2 gas first enters is the most highly concentrated acid available. You get dilute acid this way, but you maximize yield. This is called a countercurrent flow design I believe (gas up, water down, each flow in opposite direction).

Yes, I understand that some nitrous acid may form from reacting NO with water, but that’s an entirely separate reaction taking place. The reaction as I have outlined in the equation happens first. The design of the reactor can force the vast majority of the gaseous NO out of solution to be reacted with surplus air. Agitate the solution with enough available oxygen and you will have very little nitrous to deal with.

[Nitric-producer]

I have recently been experimenting with the set up described on the "species" website. I have two garden pots stuck together, with two electrodes entering each side of the pot. The electrodes are powered by a 15KV neon sign transformer which I purchased from ebay. Then a serious of water bubblers (air is blown through using an aquarium pump). Will take a few pictures and mabye a video tonight. After 2 days of continious running the PH has only reached about 2. I really did expect it to be more concentrated by now. Can anyone tell me whether im realisticly going to achieve a higher concentration before I distill? (i.e Fuming?)

I also had a go at vacuum distillation today using an old vacuum cleaner. I managed to distill at about 75 C. My product had a PH of about 0. Although the tube going to the vacuum buffer flask had some sort of white smoke - can anyone explain this?

My drain cleaner which is where I get my Sulfuric acid from is coloured purple (it is 91% acid). Did a few quick tests on it with my Nitric acid solution. When I mixed them, a lot of heat was given out and the purple colour disappeared - can anyone tell me why?

Thanks in advance.

[megalomania]

From what I know of the process it is not very likely to get much more concentrated than 60% or so. The equilibrium of the reaction does not favor the production of nitric acid as the acid concentration increases. After a certain (low) percentage you just end up running the NO2 through your acid unreacted.

I suppose if you pressurized a container with oxygen and NOx you could get a higher concentration of acid after some weeks or months. What they do industrially is a combination of either conventional distillation, or codistillation with sulfuric acid, or both. The initial distillation gives acid near the 70% mark, and the sulfuric distillation gives a nearly 100% concentration, which can be distilled again to get 100% acid. Fuming acid is then achieved by dissolving NO2 gas into the anhydrous acid.

[Alexires]

Interestingly enough Mega, when talking to my Chem teacher today, he mentioned that the Lab Assistant here makes his own NO2 for experiments on global warming and smog and other not overly interesting stuff.

How he goes about it is by running a spark plug in a glass jar, and the spark plug is hooked up to a 5kv EHT (extra high tension). So it seems that it certainly can be done. Maybe something like a starter coil from a car hooked up to a few spark plugs in a jar, then using an aquarium pump to pump air in, then through a couple of bubblers.

Just thinking about it, one of the main problems with a jacobs ladder approach is the fact that the ladder relies of ionized air (at the bottom of the ladder) to rise from the heat, creating a pathway for the plasma arc. The problem I see is that the N* and the O* will be constantly in this plasma arc, and only gets a chance to recombine at the top of the ladder. By using moving air and spark plugs, more monatomic N and O is produced, hence (hopefully) more NO and NO2.

Hell, even if we can get 10% HNO3 all that is needed for this is electricity and water we could simply distill to get 100% eventually.
Just add H2SO4 then boil off the HNO3 then just boil off the water to recycle the acid. If you're pressed for water, recycle that as well by condensing.

A hot plate, temperature probe and some accessories and you could have an almost autonomous HNO3 producer. Add in some solar panels and you're laughing.

[Nitric-producer]

After testing the PH of the gas that escapes outside from the exhaust of the bubblers, I have decided to redesign my bubblers and add a couple more. I am clearly losing precious Nitrogen Dioxides! I will try several different designs (some of which have been mentioned above by Mega), and note the efficiency of each.

In my reactor I eventually opted for a spark plug type design, mainly due to always failing at a Jacob's ladder design. Having never worked with high voltage before I didn’t realise how easily it will "jump" through supposedly insulating materials. My reactor has a 15mm spark gap - which gives a constant spark across the electrodes - I doubt that this design is the most efficient design.

Is there a website which gives exact compositions of household products - im sure I have seen it mentioned here before. I need to know what is causing the colour in my Sulfuric acid - as it is causing problems with my distillations.

[Al Sheik Yerbuti]

Might there be a way to fix the NO2 so that it precipitates out of solution? I don't remember if there are any nitric salts insoluble in water, but what about a different solution, EtOH or acetone, etc.? How about the Ca(OH)2 route?

Another workaround: How would the yields improve if bubbled through sulphuric acid?

(It won't let me edit my last post.) (but I can - mega)

About the best I can find is that KCl is soluble in alcohol but KNO3 is not. So it would presumably precipitate. Um, lemme back up, if KCl were saturated into alcohol and our enriched gasses were bubbled through, I'm guessing that some of the K would react with the recently fixed NOx and precipitate out. I suppose the Cl would evolve as Cl2.

Another route is bubbling the enriched gas in water, through KCl solids. KCl is somewhat soluble in water but KNO3 is highly soluble. The KCl would saturate but as it reacted with the NOx, supposedly more would dissolve to maintain saturation. Supposedly the KNO3 would increase in concentration and Cl2 would evolve. You could monitor progress by watching the KCl solids disappear. When the solution is doubly saturated, it can be dried and alcohol used to remove any KCl left. At least this last part is real, I was able to verify this separation.

As far as the rest, I really need some better chemist than I to verify (or come up with something better, is OK too)

[NGfan]

Anniesland U.K, fractional distiller?

I have begun the task of making HNO3, and I've made a short vid on YouTube which demosntrates the speed the NO2 gas forms at, but I am putting the project on hold if I have to go out and buy a rotavap to get 100% HNO3. From what megalomania has said, I understand that agitating the solution with oxygen will minimise HNO2, but do you mean during, or after you've made the HNO3, and is it 100% oxygen, or can you just push out more air than you do nitrous gasses?

Also, what will the HNO2 do if it was used in making HE's? It'd be nice if there was more research into it. Wikipedia says it decomposes into NO2, water and Nitrogen dioxide, which can't be that bad, if I knew how it was that it decomposed. Ah well, looks like a thorough scouring of the internet is imminent.

Wait, this website http://www.ucc.ie/academic/chem/dolchem/html/comp/nitric.html states that if the HNO2 is heated, it forms HNO3, water and nitric oxide. Now, to find that heat...

[fractional distiller]

Ngfan- I hope this helps you out.

Well first of I would love to see the video of you producing NO2, please post the link! Second do not put your project on pause because there are many ways to get pure HNO3, it is possible for you to deviate from Mega’s process. We all will have to very slightly how we construct our reactors due to budgets, space constraints and endless other restrictions/ramifications.

To answer the purposed question that ,I am guessing you are asking, agitating the mixture with O2 to reduce the amount of HNO2 in your final product can be done many ways. Agitating it with surplus oxygen as it is being broken apart in the reaction chamber is what I plan to do, but it can be done after wards as shown in your site ( http://www.ucc.ie/academic/chem/dolchem/html/comp/nitric.html ) under the Oswald process but that is an entirely different set up, because of my design. Which the as of this moment two ceramic jars and a Jacobs ladder or spark plug depending on which is more cost efficient, easier to set up, and most important practical/efficient. A pump will feed air into the chamber and I will agitate the mixture with O2 by just adding a small inlet hose into my pump and just allowing O2 to feed in, but I will explain that momentarily.*

The problem that the air we are using for the reaction for our HNO3 production is 78% N2 and 21% O2 with 1% trace gasses that wont matter. So if you have a liter of air you have 780ml of molecular nitrogen and 210ml of molecular oxygen. Since Mega was kind enough to give us the final part of the formula you can calculate it as such.

1 liter of air consists of 780ml of N2 and 210ml of O2.
N2,O2 => 2NO /a 1:1 ration of molecules 2 Nitrogen too 2 Oxygen
2NO + O2 => 2NO2 / Now the ratio is 2:1 Nitrogen too Oxygen
3NO2 + H2O => 2HNO3 + NO/ Ratio still stays the same, just the addition of water.

So to answer your question yes add O2 to it as it is reacting and I am pretty sure you want to use pure O2 because anything else will just mess up your reactants and may result in unwanted by products.

* As I had mentioned above the Oxygen will need to be added as the reaction takes place and a large quality will be needed to maintain a fast and effective and efficient production of NO2. Considering the math I have shown above you will need a 2:1 ratio for the amount of Nitrogen you put in via my method.

So for every liter of air you put in you need 1.56 liters of O2 to keep the equation balanced. I will probably be producing my O2 by electrolysis of H20. I will be using electricity anyway to run the reactor so a little more plus some tap water and salt as an electrolyte wont hurt. LMAO If will be using 3.12 liters of water and about 5 amps to yield the 1.56 liters of O2 I require.

Secondly your question concerning the impurity of HNO2 in HNO3 the problem I see with this in HE’s is that it cant be beneficial my RDX creation as graciously introduced to me by mega calls for pure HNO3 so I don’t want any HNO2 in it screwing up my yields. Yes HNO2 does decompose if heated but so does you HNO3 so effectively by trying to purifying you acid by heating ,if that is what you are implying, will only leave you with a less useful product then you started with. I don’t care about the extra NO from the reaction because it will just be absorbed into the HNO3 (I think it may be wrong) in that case I have fuming nitric acid at my disposal or I just decrease the pressure with the handy vacuum pump and that pesky NO goes away!

Hope this helps! Anyone if I did my math wrong or made some blatant mistake or any mistake please do not hesitate to point it out.

Best of Luck.

[Nitric-producer]

After about a week of running the reactor, I have obtained about 3 jars of Nitric acid. No matter how long I left them - the PH would not go below 1! It's quite cold here just now, between 0 and 10 C most days, so my water was nice and cool. So if you build your own reactor, stop running after you get to PH 1 - otherwise you are just wasting electricity.

On the subject of obtaining Nitric by using a base solution. I plan on doing this method after I build my "Contact process" reactor. For me - Sulfuric acid is to hard to obtain in large amounts so I plan to recycle it. However when I can make my own Sulfuric I will try this:

Having my bubblers filled with a concentrated solution of NaOH - with a PH of 14. As NaNO3 is a neutral salt - when the PH goes to 7 - you will have used all the NaOH. If you know exactly how much alkali you used, you can calculate yields etc.

However can anyone remember the formula for changing Ph values into concentration of acid values? Just so I can calculate how much Nitric I have.

More progress next week when the rest of my vacuum set-up arrives.

[NGfan]

Wel, thank you muchly for your reply, fractional, but you ommited wether or not you were reffering to Anniesland in the U.K, as I live far, but not too far from it.

*Sigh* I hate having to make my own O2, and as well as that, I'll have to make some sort of regulator to control the input, so as not to waste it... This is turning out to be harder than I first anticipated, so I think I'll overbudget, and buy some more equiptment.

I also find, as they're are extremely high voltages, that even wood conducts, and I have to use plastic from wall sockets.

The YouTube vid is here; http://www.youtube.com/watch?v=dScqzU7UGHk but the camerawork is shoddy, and YouTube actually cut off the last thirty seconds, in which it steadily got redder inside. It was also just a shoddy beta-version, a nice B-E reactor will be in in the not-to-near future.

I am also doing this for RDX, but I think it (HNO2) produces VERY unwanted by-products, rather than poor yeild. Well, RDX first, then anything really.

[Alexires]

Nitric-producer: As pH = -log[H+] ions, then you can say that

[H+]=10-pH

I hope that is what you are looking for. Hence, if you get an answer saying 10, then you have 10mol/L of hydronium ions, and hence, you have 10mol/L of dissociating acid (doesn't need to be straight HNO3. For instance, if you have HNO2 contaminants, then it will fudge your answer somewhat)

If you know your acid is pure, then that will tell you the concentration of your Nitric in mol/L.

Also, to anyone whom might be emailing me, you should PM on the forum. My email isn't working at the moment. Also, use an email that doesn't contain your name for gods sake. You have no idea who I could be.

For all you know, I could be LEO or some other kind of "terrorist".

RTPB people, RTPB.

Also, NGfan, I watched your video. Very interesting after only a few minutes use. What was the input into your NST? Would it be possible to hook it to solar power or something that cannot be traced?

You might want to try now hooking an aquarium pump up, pumping air into the chamber, bubbling the air/NO2 through a few water traps and taking a pH test of it, or just simply seeing if you get any result.

I'm pretty eager about this idea, seems like a very possible way to get HNO3.

I cannot seem to find any data regarding the decomp. temp. of HNO2, although an article (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11237042&dopt=Abstract) I just read says that its concentration in HNO3 decreases as the temperature approaches 50*C. I'll have a look at a merck index tomorrow and see what it has to say, and what options we may have.

Another thing that occured to me would be to use some kind of sonic wave to cause the HNO2 to break down, leaving the HNO3 intact if there is no other way of removing it from solution. This came from the same article that said you can produce HNO2 by hitting HNO3 with ultrasonic waves. Ill post results soon.

[megalomania]

HNO2 will eventually be oxidized to HNO3 given time, but I don't have any references on that at the moment, or under what conditions it can be accelerated.

There is absolutely no reason to use pure oxygen in this reaction! They do not do that industrially. Use a surplus of compressed air from a fish pump or air compressor run through a bubbler. NO is highly reactive to oxygen, even in small amounts, and will form during the reaction at such a rate that it is essentially merely an intermediate.

[Alexires]

Not to mention the explosion hazard if you are cracking water *shudder*.

Mega, I thought that HNO2 broke down into its constituants (NO and H2O).

We all admit that from this project, to get nitric acid of a decent grade (80%+), then we are going to need to vacuum distil. So, personally, I wouldn't worry about the HNO2 in the acid. You aren't going to be making RDX from the acid straight out of the reacton, you are going to need to distil first.

On a different, I consulted the merck index today to find nothing. No specifications for HNO2.

I am at a loss of what to do.

My chemistry teacher (when consulted) said that it might be possible to use H2SO4 to oxidise the HNO2 to HNO3, but that was just a vague thought.

Another possibility that just came to me may be freezing HNO3 to seperate it instead of heating it. Just a random thought.

[megalomania]

There are other threads discussed over the years about distilling and concentrating nitric acid. That is putting the cart ahead of the horse at this point. We need to get fixed nitrogen first.

If nitrous acid does break down to NO then that NO would be oxidized to nitrogen dioxide which would then form nitric acid. Perhaps this is why air is bubbled into colored nitric acid to make it white?

I should mention that the nitrous acid needs to be left out in the open air, uncapped/unsealed for it to eventually form nitric acid. I have a book here that says nitrous is highly unstable, and readily decomposes to NO with ease. Apparently passing chlorine gas into nitrous acid forms nitric acid and hydrochloric acid. Also the book says the most concentrated nitrous acid can get is 0.2N, at which point it is exceedingly unstable.

Also I should qualify my last post by saying adding some additional oxygen can help the reaction since we would achieve a maximum equilibrium at a 50:50 mix of oxygen and nitrogen. Since producing oxygen might be uneconomical for some, it is entirely optional. Pressurizing the reaction vessel would also bring more air into contact with the electric arc. Again, that is entirely optional.

[Al Sheik Yerbuti]

I came across some info from
http://www.inchem.org/documents/icsc/icsc/eics0930.htm
concerning NO2 which contained in part:
Boiling point: 21.2°C
Melting point: -11.2°C
Relative density (water = 1): 1.45 (liquid)
Suddenly I realized what is happening in my "still"! In reacting Sulphuric acid with Potassium Nitrate, I have NOT been making Nitric acid, but what might be called anhydrous nitric acid; in other words, NO2! Now this is a very important distinction! I have been optimizing my reactor to maximize the density of NO2 fumes, as evidenced by the visually measured density of the fumes. These fumes are passing into my collection vessel, where they are cooled by ice packs, which can easily cool the vessel below 21.2°C! That's 70F. Other properties found on that page confirm this assertion, such as the yellow color of the liquid and my density measurements the other day were at 1.44 something. At the time I thought My measurements must have been inaccurate because I expected closer to 1.51 for 100% HNO3 but this new info seems to confirm this particular measurement and its interpretation.

Funny, I had been concerned that I had too much water in the Nitric acid, but since liquid NO2 reacts with water to make HNO3, I have actually not had enough water! Heck, I could use the liquid NO2 to consume the last 2% of water in Sulphuric acid to produce an ideal nitrating solution.

No results for the plasma cutter yet. I promise today, though.
__________________________________________________ _
LATER...
I bubbled the plasma from the torch into distilled water. I did this for maybe a minute total. The water became very warm. It was splashing everywhere and was obviously an inefficient setup. I was unable to detect any change in pH from litmus. There was the unmistakeable odor of NOX. I'll set up a more efficient method, as the odor is encouraging for sucess. I'll also try alternative methods of capturing the loose NOX in solution as I have previously discussed. Photos are click-to-enlarge.
http://img251.imageshack.us/img251/5747/plasmanox01vd6.th.jpg http://img63.imageshack.us/img63/6605/plasmanox02rc4.th.jpg (http://img251.imageshack.us/my.php?image=plasmanox01vd6.jpg) I referenced my "still", here's a pic: http://img443.imageshack.us/img443/4982/hno3generatoric6.th.gif (http://img443.imageshack.us/my.php?image=hno3generatoric6.gif)

[NGfan]

Well, that is a releif, Megalomania, as I was sure I'd have to put in lots more work to make the HNO3 uncontaminated. I've also jumped a few hurdles in terms of problems, so I'm fairly optimistic about the project. I still need to find out how long the transformer runs before overheating.

Alexires, my transformer uses regular mains at 240v, with 2.5A. The output is 10kV at 50mA. The gas takes a while to form though so it actually got redder after the end of the video, but for some reason YouTube cut it off.
I'm not sure if it is possible to hook it into solar panels or something, but you'd need a pump too.

I will be testing soon, but not too soon as I want the finished product to be perfect, as it involves much dangers: toxic gas, acids, high voltage electricity and a chance to become homeless if it's too inefficient (electricity bill).

I have decided not to add surplus oxygen, even though a friend of mine actually has quite a few canisters, as it's just too much effort for little gain.

[Chris The Great]

HNO2 readily decomposes in highly acidic conditions, anyone who has ever added a strong acid to a nitrite knows this. Simply put, I am absolutely sure in saying that there is no HNO2 in the nitric acid and that you should all stop worrying about it.

I think time would be much better spent finding what common materials (plastics and metals) are not attacked by NO2, dilute nitric acid and concentrated nitric acid. What performance do standard plastics have against the chemicals? Are they destroyed, damaged above a certain temperature or unaffected? Such information is essential in designing a suitable reactor and really should be the top priority for this undertaking as experimentation is going to be difficult if nobody knows what can actually be used to build the setup so it will last and not contaminate the product! Nobody likes finding out the hard way that component X of their design is not actually immune to NO2 gas and having to start all over...

[Alexires]

Thanks Chris, that is useful to know. Anything to back it up? Of course, I wouldn't be suprised as Nitric Acid is a strong oxidiser, and should oxidise HNO2 to HNO3 (I'd hope).

On corrosion resistance -

http://www.mext.go.jp/english/news/2000/09/000961.htm
States that because of a lowering phosphorous content in stainless steel, it has improved corrosion resistance against nitric acid.

Corrosion resitstance chart for gaskets and stuff. - http://www.akrongasket.com/chart1/newchart40.html

This (http://ptcl.chem.ox.ac.uk/MSDS/glovesbychemical.html) website thinks that PVC is suitably corrosion resistanct to nitric.

Ofcourse, we aren't just talking about concentrated nitric, we are talking about boiling nitric.... which is about a fucktonne worse.

Also, mitsubishi metals has this (http://www.mmc.co.jp/alloy/english/products/taisyoku/gijyutsu2.html#15) to say about corrosion resistance to boiling concentrated acid happiness.


Seriously though, a couple of hundred dollars to buy a decent vacuum setup is sort of a must. Most of these things are titanium alloys, and you can't afford them over glass. Go the glass.

If you are going for a BIG setup for making nitric, still buy glass *laugh*. Either do it in batches, or use big flasks.

PS. This (http://stainlessandalloy.thomasnet.com/item/special-fabrications/custom-bending/-nbsp-1220?&forward=1) says that stainless is "satisfactorily resistant" to boiling 65% nitric acid. Include a little low pressure, and as long as you keep the temperature below 70*C it is "fully resistant" or so they say.

That looks better - http://www.nickelinstitute.org/index.cfm/ci_id/10626/la_id/1.htm

Also, something I picked up as I was looking around was this - http://adsabs.harvard.edu/abs/2005RaPC...73..213K

Unfortunately, I can't find the article. It would be interesting if we could make HNO3 via some kind of EM radiation.

[Nitric-producer]

In my chemical engineering book, it states that in plants where Nitric acid is produced, Aluminium is always used. (same for Sulfuric acid) This is because Nitric and Sulfuric are oxidising acids and when in contact with Aluminium they form an oxide layer over the metal protecting it!

In my reactor I have used a dessicant chamber to dry any air entering the rection chamber - there has been no corrision anywhere in the chamber. My problem is my bubblers and corrision! Silicone sealant and epoxy are both eaten by Nitric acid - they did not work. PVC tubing however is not corroded. My new design mainly encorporates glass and aluminium.

[Al Sheik Yerbuti]

I have found that using a liberal amount of teflon tape as a gasketing material resists nitric corrosion. For those few who don't know, teflon tape is extremely common in plumbing and pneumatic work. It's the white stuff in the white and blue spools.
---------------
EDIT:
Harbor Freight has solar panels up to 50 watts. They output 17V to charge car batteries, but I've seen cigarette lighter power converters (to household current) at Wal-Mart for (I think) $12.

W=VA so 50=17(3) and 50=120(0.4). And that is only at peak sunlight.
--------------
EDIT #2:
wind power is more advanced than solar.
If you're rich, go here: http://www.bergey.com/
If you're poor (or handy and/or frugal) go here: http://www.otherpower.com/otherpower_wind.html

[NGfan]

Well, right now I'm building a prototype to see what factors I will have to account for, such as materials. After letting it run for a while I'll check to see which materials have corroded and what problems I have encountered and then build from there.

Although it would be nice to have an independent, continous supply of HNO3 that was untraceable, I'd just buy a petrol powered electricity generator if I was looking for that. As it is, if the piggies can manage to trace me from a slightly incresed electricity bill, then I'll be impressed.

[Chris The Great]

I guess a good idea would be to simply boil different materials in nitric acid of various concentrations to make sure it's suitable. Hopefully I'll be distilling some fuming and 70% nitric acid this weekend, although I'm sure there are tons of people here with a bit of extra acid who can do some tests as well.

I was under the impression that aluminum was only resistant to concentrated nitric acid, and not diluted acid. Obviously it would be very easily to find out by adding a piece of Al to some 70% in a test tube... I imagine that aluminum nitrate is insoluble in higher concentrations of nitric acid as well, which will keep the oxide layer from simply dissolving away as the nitrate...

But it's great to hear PVC is resistant, as lengths of pipe could then be used for the absorption tower. I am going to go with the Ostwald process myself but the actual engineering difficulties are the same (or at least very similar).

(edit) As for the HNO2 thing- no, I don't have a reference, and there probably isn't one since you guys searched and turned up nothing. It's experimental data from other hobbyists. Also, a method for producing N2O3 is reducing nitric acid with starch. Obviously the reduction product, HNO2, is not stable and immediately breaks down, otherwise the preparation wouldn't work...
2HNO2 -> H2O + N2O3 (NO + NO2)
I can dig up a link demonstrating that if anyone would like it.

[akinrog]

Suddenly I realized what is happening in my "still"! In reacting Sulphuric acid with Potassium Nitrate, I have NOT been making Nitric acid, but what might be called anhydrous nitric acid; in other words, NO2!

Anhydrous nitric acid is N2O5, i.e. nitric pentoxide. And IIRC from my education (years ago), when you chill NO2 to liquidate it, it becomes N2O4. Regards.

[nbk2000]

N2O3 is condensed as blue liquid from a mixture of NO and NO2.

http://www.cci.ethz.ch/experiments/darst_N2O3/en/stat.html

[Nitric-producer]

Ok just tried making some Sodium Nitrate from the Nitric I have made using my reactor. Neutralised acid with Sodium Hydroxide, boiled off water. Stopped when I had about 20ml of solution left. The liquid had some kind of orange colour, almost a precipitate. Any ideas anyone? Anyway baffled by this - I boiled off all the liquid - I then got what looked like boiling sugar? Once cooled a hard brittle solid has formed.

Its in a big chunk, some of which I powdered and burned with paper - which fizzed nicely. Like an oxidiser. So can anyone shed some light on this orange colour and do I have NaNO3? It physically does not look like it.

Does my reactor somehow get impurities from somewhere?

[megalomania]

Did you use city water, or distilled water? Who knows what evil (ions) lurk in the heart of city water...

[Nitric-producer]

I used "city water". However after more observation, the orange colour has precipitated out completely leaving clear liquid and orange precipitate. It looks like Iron Oxide. Although I dont know where its from as there is no iron in my reactor? Anyway, I came home early to finish my new bubblers, hooked them up and they would not hold a seal - so I'm back to the drawing board. Again! I'm really stuck now. :confused:

[chemdude1999]

If you have old galvanized pipes, that could be a source of iron. City water is usually free of iron (at least compared to well water). However, I have ran my city water on an AA spec, and it does show all the metals. BUT, it shouldn't be near enough to cause oxide precipitate.

Trace the problem back from the tap. Maybe give the water company a call. Tell them you are worried about a new salt water aquarium you are setting up.

My guess is the impurities are screwing your seals up. Break everything down and clean it well. Good luck.

[megalomania]

When the city flushes the hydrants the level of rust in the water increases significantly, that's why they do it though, to flush that crap out of the pipes. They are always flushing some hydrant somewhere it seems, so maybe you just got unlucky. Still, that's why you never use city water in the lab...

I ordered a HV source yesterday, and my electrodes still have not arrived :(

[megalomania]

Grab your top hats and get the Delorian up to 88.5 because we are taking a trip back 100 years to find out what the ancients had to say about nitrous acid.

Nitrous acid is very unstable, this I have mentioned. I now have references… Aqueous solutions of nitrous acid upon warming decompose to NO leaving nitric acid:

3HNO2 --> HNO3 + 2NO + H2O + 30,770 cal.

This decomposition will proceed in the cold in the presence of rough surfaces (sand, glass fragments, etc.). Saposhnikoff, J. Russ. Phys. Chem. Soc., 1901, 33, 506. Lewis and Edgar, J. Am. Chem. Soc. 1911, 33, 292.

Naturally life conspires against me and my proxy to pubs.acs.org is down… At least the first page is free, so everyone can peruse it at http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/1911/33/i03/f-pdf/f_ja02216a004.pdf

The solution of the acid is more stable in the presence of nitric oxide under pressure Helv. Chim. Acta. 1920, 3, 366.

I could go on, but you get the point. The stuff is unstable, it spontaneously decomposes as soon as it exists, and a bottle full of broken glass would get rid of it nicely, especially if gently heated.

[Nitric-producer]

Just been doing some thinking, and have been wondering about Dinitrogen Tetraoxide (N2O4). According to my search below 21 *C it becomes a liquid. If some effiecent way of cooling the gases could be obtained after exit from the reactor, it would be so much easier just to mix N2O4 with water. Could Pure Nitric be obtained this way (or almost pure) ?

Info on N2O4 : http://en.wikipedia.org/wiki/Dinitrogen_tetroxide

[Frunk]

Could Pure Nitric be obtained this way (or almost pure) ?

Info on N2O4 : http://en.wikipedia.org/wiki/Dinitrogen_tetroxide

Info from the same damn page:

Intermediate in the manufacture of nitric acid

Nitric acid is manufactured on a large scale via N2O4. This species reacts with water to give both nitrous acid and nitric acid:

N2O4 + H2O → HNO2 + HNO3

The coproduct HNO2 upon heating disproportionates to NO and more nitric acid.

[nbk2000]

A journal article from the 30's about using air to produce high-purity NA, free of NOx.

[Nitric-producer]

Frunk: Sorry if my post was unclear, what I meant was if you mixed 1 mol of water with 1 mol of Dinitrogen Tetraoxide, would it give you 1 mol of HNO3 and 1 mol of HNO2 - as the equation states. The problem I am having is that with NO2 and water, you need a large quantity of water to dissolve any NO2 in. Giving low concentration acid.

I guess what im gettin at is, if I where to mix a certain quantity of water and N2O4 - would I get anhydrous Nitric acid, with anhydrous HNO2?

Thanks.

[megalomania]

As these things usually work it can be difficult to get the reaction to go to completion, Le Chat's principle and all. It may take time, maybe on the order of weeks in a sealed container, for the reaction to complete.

Not all reactions are like that of course, it depends on the reactivity of the reagents involved. I don't imagine dinitrogen tetroxide is all that reactive with water to the point it will react instantly and to completion, but I have no concrete data either way, so I could be mistaken. With constant agitation and minor heating I bet eventually you could get an anhydrous product.

[Nitric-producer]

Thanks Mega, that sounds promising. My friend who is an "overclocker" told me about devices used for cooling PC CPU's. One he mentioned was a Peltier. Put simply when you give it power one side gets very hot and the other gets very cold. I plan to purchase said device and possibly a mini fridge. However got to many projects on the go at the moment - Aldehyde reactor, Contact process, the list goes on...!

[Nitric-producer]

Lots of recent developments:
Tonight I tried a Nitric extraction using DCM. Started boiling off DCM, I must have went to far and fairly soon I got thick red fumes of NO2. I killed the power and sat the whole beaker outside. Got some nice red acid.:(
After some reading of my textbook - I came across this:

O3 + 2NO2 --> O2 + N2O5

As N2O5 is the anhydride of Nitric acid, once dissolved in an exact amount of water it forms Anhydrous Nitric acid without any HNO2 or other rubbish! :D
I am now thinking feed NO2 from my Nitric reactor into a second chamber filled with Ozone, keep the temperature below 20*C - and you get some nice N2O5 :D . Imagine pure anydrous without any messy extraction techniques, as detailed above! :(

[megalomania]

Since the electric arc makes no small quantity of ozone as well as NO2, cooling the gasses or compressing them in anhydrous conditions might be a good way to make N2O5. Liquefying NO2 makes N2O5 anyway, but the presence of ozone should improve the yield... if your reference is really as simple as you have indicated.

[Nitric-producer]

An interesting page:

http://www.ijvs.com/volume2/edition1/section2c.html

[Nitric-producer]

Ok, here's what im planning next:

The Nitric reactor is run as normal except the NO2 is condensed by cooling to form N2O4. The whole thing is turned off, and the air pump is swapped for an "electrolyisis of water" device, which feeds the reactor with pure oxygen, which before entering the reactor is bubbled through a dessicator probably filled with concentrated Sulphuric acid? The spark gap then converts the O2 to O3, which is then bubbled through the liquid N2O4. What im hoping will happen is that N2O5 is formed and can then be collected. Mix with water and you get 100% anydrous Nitric acid.

Can anyone see anything wrong with this setup that ive missed, before I spend a week trying to build it?

[mr.pyro]

Just wondering how are you going to keep the H2 separated from the O2 and out of the spark gap?

That could cause a nasty mess.

Something like this: http://en.wikipedia.org/wiki/Image:Hoffman_voltameter.jpg

[megalomania]

Nothing sophisticated is required to keep the hydrogen gas out.

You could place the electrode generating the oxygen into a plastic pipe. The length of the pipe is longer than the electrode. When the works is immersed into water, the oxygen gas goes up and is channeled into your ozone generator.

The only problem I see is that you would need tremendous amounts of power to produce enough oxygen to get pure oxygen beyond a minuscule amount. Why not just use a traditional ozoneator?

I have done many ghetto electrolysies in my day, and you don't get a whole heck of alot of anything despite days and weeks of running the thing. Your spark gap is already cranking out ozone as well as nitrogen dioxide, why not settle for that.

What I can't tell you since I don't know myself is the percentage of nitrogen oxides produces by the electric arc. Keep in mind you consume oxygen to produce nitrogen oxide, more oxygen is consumed to produce nitrogen dioxide from the nitric oxide, and yet more oxygen becomes ozone. From anecdotal observations I have heard many people describe, ozone will be produced in the most significant amount. I read only one scientific reference that described nitric oxide production as only being a few percent relative to the volume of air run through the system. My hypothesis is that there is sufficient ozone present from the spark to react with all of the nitrogen dioxide produced. Some experimentation may be required...

[Nitric-producer]

The only reason for seperating the procedure is because of yields. I looked at Ozone producers on ebay, and they only seemed to produce a maximum of 400mg of Ozone per hour, after some calculations this only amounted to 16ml of Nitric every day assuming 100% reaction completion. If I had some idea of how much Ozone my reactor makes, I would know if it was worth just running using air? I guess I will need to do some experimentation. Unfortunately my funds are rather low at the moment. :p

[Darkover]

I've been watching this thread with great interest. Other than Nitric-producer, has anyone done this ?

[Heat]

I've done it. It was almost a year ago (I've been busy with personal problems for the last year), but I do intend on making a new and better one.

The method does actually work, but you have to sweat for it if you want usable amounts.

I used basically the same setup as the guy on species8472.dyndns.org. My power supply was a 7500 volt NST. I had a large glass jar, into which I pumped air using an aquarium pump. I had a pipe that pulled air out from the top of the jar into my bubbling chamber. The bubbling chamber was a glass jar filled with distilled water. The bubbler was a glass pipe with some holes in it, wrapped in fiberglass which was held in place by teflon tape. (This was to reduce the size of the bubbles, since a simple mathematical calculation showed that reducing the bubble size by a factor of N, increased the effective reaction surface area by a factor of N. Not to mention that it reduces splashing)

At first, my yields were very low. (It took a few days before I could get baking soda to even bubble.)

So I had to start working out the problems. The first was that my reactor was leaking like crazy. No glue that I could find held out under the heat of the arc. Not to mention that NO2 itself is quite corrosive. I ended up setting up a 555 timer circuit which was connected to a relay that switched the NST on and off. I think the duty cycle was something like 30 seconds on, and 15 seconds off.

The next problem was that the NO2 yield was very low. I figured that out, too: I had set up my arc as a Jacob's ladder, but the top of the ladder was smooth, and too wide, so that the arc couldn't hold itself there. So it was continuously breaking and restarting (several times a second). Originally, I thought that was how it was supposed to be, but it's not! The idea is that air has to pass *through* the arc, but when the arc is rising, it's just moving with the same air.

So I changed the design: I had two sharpened nails, wrapped in copper wire to act as a heat sink. The nails were attached to a simple hydraulic system I made with a couple of water-filled syringes, so that I could manually adjust the distance after I closed the jar, even while it was running! So I'd hook up the power, pull the nails together, and then pull them out to the desired arc length.

I think after the first night that I ran this system, I finally had acid that would bubble nicely when I added baking soda.

It worked pretty well, except that sometimes the arc would go out. So I added a timer based system that passed a round metal object between the nails every few seconds, to "ignite" the arc.

But then everything started leaking again.. and I never found time to fix it.

Anyway, I scrapped that desing and I plan on making a new system. I'm just trying to figure out how to make proper seals.. Last time about half of my connections were leaking.

By the way, I think the NST (Neon Sign Transformer) is very ideal for this kind of project. I bought mine used at a neon sign shop for about $10. They provide a nice clean supply of high voltage current, and are current limited, so you don't have to worry about blowing anything, even if you short circuit the output.

I also have a picture, but it won't let me make any attachments. (it doesn't even show the option)

[stupid939]

As soon as I get an aquarium pump I will make one. I plan to use PVC or glass for the spark-gap chamber, and I have a 9KV 30ma transformer that I used for a tesla coil. It should be suitable for the project.

I already attempted to build the blower/spark assembly, but it did not work because I had a microwave fan blowing air through the chamber and it did not create enough pressure to bubble the gasses through water. I will try to pick up the pump in the next few days, and I will put up a tutorial or something with lots of pictures (tutorials are hard to find these days, aren't they?).

Nitric-Producer - If you have any suggestions on the construction of the chamber, let me know so that I won't have to find mistakes and remake it.

[Nitric-producer]

Heres some pictures of my first setup:

http://i155.photobucket.com/albums/s296/minioneandrew/DSC00233.jpg

http://i155.photobucket.com/albums/s296/minioneandrew/DSC00225.jpg

The 1st picture shows the entire setup: From left to right, an aquarium pump, a dessicator chamber filled with NaOH, the 15KV supply, the terracota reactor, and the 2 bubblers.
The 2nd picture shows a close up of the spark gap. Sorry about the low quality images.

This setup has now been abandoned due to the Nitric dissolving the seals of my bubblers. The reactor itself has no leaks, due to there being no moisture inside, i.e no Nitric. I am in the process of building a website to give better details. Silicone sealant and epoxy are not nitric resistant. PVC pipe is however. Hope this helps.

[Frunk]

I assume the flexible pipes are some form of transparent PVC?

Anyways, good job. I like your setup, and even more given that it cost 50$. :D

This forum may get pics of my future setup during the summer.

[Nitric-producer]

Yeah just flexible PVC pipe. Bought from hardware store. Id say if I didnt have the failures this time I could go out and buy the whole lot for 20 dollars, not including the NST. Id advise anyone wanting to build a reactor, just make sure everything is dry. Sealing is so much easier, without having Nitric dissolving things.

++++++

Id is a psychology term. Perhaps you meant I'd, as in I would? NBK

[hydra]

On the previous page...

http://www.roguesci.org/theforum/showthread.php?t=4181&page=4&highlight=electrochem%2A

nbk2000 has an attachment in one of his posts, a rar file of a 1930's journal article.

I cannot get that attachment to download. Right-click and 'save as' did not work; and a direct click on it also did not work.

Both actions did bring up my 'download' menu, but all that was saved was something called "attachment.php"; which is very small and not a rar.

I tried opening it in another tab (Firefox), to see what kind of error-msg I might be getting; but that didn't work either. It again opened my download window.

Has anyone successfully gotten that attachment; and if so, what procedure did you use?

thanks!

EDIT: Found the answer, sort of. Just opened that "attachment.php" page in Notepad, and discovered that it's trying to put up the "You are not logged in or you do not have permission to access this page" message.

Does anyone know if that journal article is on tmp's FTP; and if so, which directory it's in? thanks.

[stupid939]

Hey Nitric-Producer, did you seal the terracotta pots with epoxy? It looks like you sealed the air inlet, nuts, and joined the pots together with epoxy. I know that the epoxy won't hold up to the nitric acid, but your setup leads me to believe that as long as no moisture is present, the epoxy in the reactor should stand up to the NO2.

I went out today and gathered everything I needed, and I started assembling it. I have the bubblers done, and I am going to work on the reactor next. I am only waiting to see if the epoxy will be fine to use in the reactor.

I may end up using the terracotta pots instead of PVC, but the only problem I see is disassembling the reactor.

Everything for the project, besides the NST, cost me $18.82, and I even bought some extra stuff. I am taking pictures, and once it is done, I will put up a tutorial on my site and probably create a PDF.

[hydra]

mega, in regards to oxygen-production...

Perhaps your trouble with getting useful quantities was due to not using enough current? The process actually can produce quite a bit of gas per Kwh of energy...about 150g/kwh for a normal 2-gas cell; and double that for depolarized cells. Another advantage of using an air-depolarized cathode is that no hydrogen is given off at the anode; so the "separation problem" is solved.

The type of cell I'm talking about also does not consume any reactants other than water.

One must realize tho, that at the cell-voltage involved (1.5 volts), even a single KwH represents a pretty high current....i.e., 660 amps!

That's in a realm that's a little hard to work with... :D

Anyway, if you were running just a single cell, and weren't running more than 5-10 amps, you can see that the output in grams/hour would be disappointing, for sure.

However, 50-100 amps is entirely doable with common equipment and materials. And that would be about 30-50 grams/hour per cell.

Since it's inefficient to lower a 'normal' voltage PS to 2v with resistors; the common solution is to run several cells in series.

A properly made depolarized cell will run 1.2 - 1.5 volts per cell; so 3 cells would be just about right for a typical high-current 5vdc surplus PS; like a PC PS.

7-8 cells is probably optimum for a 'typical' 12vdc battery charger (which runs 16-17v no load, to about 11-12vdc at max current).

fyi, here is a good early writing on producing oxygen with an air-depolarized cathode instead of a regular cathode:

GAS-pat2390591- ELECTROLYTIC METHOD FOR PRODUCING OXYGEN - Janes.pdf

It also includes some info on making the cathode itself (methods and materials are well within range of home-shop, btw)


If I have my numbers right...

1 gram mol. weight of any gas is about 22.4L at STP.

So O2= 32g/22.4L, and a cuft= 28.25L. So a cuft of O2= 40.35g

Assuming a 50amp current-level through 8 cells @ 1.4v/cell, your power-rate would be about 500whr; so about 150g/hr of O2 production.

That'd be roughly 100 liters/hour...not too shabby. (equals 4 cuft per hour)

The nice part is that the price is right. At 10 cents/khw, you're looking at only 5 cents per hour to run at this rate; or about a penny per cuft. That'd be about $2.50 for the typical 250 cuft welding cylinder...which the welding-gas place charges around $30 bucks to fill.

I believe those little $15/12vdc tire-inflator compressors are totally oilless (teflon ring I think?), so with a little care, you should be able to compress the O2 to around 100psi, into an empty 5-gal freon or propane tank for example. It'd probably be prudent to flush either of those tanks with N2 first... :D

That'd give you a decent storage-volume; and a more convenient pressure for later use in experiments.

The biggest problem with air-cathodes is their fairly low current-density capability. However, a LOT of work has been done on this issue over the years. If there's any interest, I'll post some info I have on that; but this may not be the right thread for it anyway...??

In any case, with a cell that doesn't evolve hydrogen, physical design and construction constraints are much relaxed; making it a lot easier to just use large-area electrodes to get around the low current-density limit.


fyi, I did a search for 'electrolysis', but did not find a thread specifically about producing oxygen. So, since it has already been discussed in this one, I went ahead and posted here. But if there really isn't an oxygen-thread yet, perhaps it'd be worth starting one?

edit: but in another search, just came across " Generating Oxygen Gas for the Production of Nitric Acid - Archive File"; which seems like it's still an active thread; so maybe this belongs there.

[Nitric-producer]

All the reactor seals are done using Silicone sealant, I bought the all purpose stuff for sealing in kitchens. This includes all the inlets/outlets of the reactor. Most seals used PTFE tape alongside the above.

The terracotta pots where dried in an oven before construction started, to remove any moisture. The dessicator dries the air entering the reactor, which means water content is very low. After weeks of running the inside of the reactor showed no signs of corrosion anywhere - apart from the aluminium electrodes - but I assume this is because of the high energy spark.

I used epoxy resin on the bubbler seals, it seemed to stay in hard lumps, but lost its adhesion to the surface. I then tried silicone sealant, which dissolved even quicker. The current design use's nuts and PTFE tape, which so far has held up completely, however was difficult to make.

However although it took a while to setup, this method actually works. If left on for a few days I could produce 1L of 50% acid, and it feels good knowing you made it from air and electricity. The project is currently on hold, as I am attempting to design a unit which produces anhydrous Nitric. :D

[Alexires]

While looking for a source of NST in Aus and comparing microwave high voltages with them, I found this (http://www.rtftechnologies.org/emtechnologies.htm). Rather interesting. I think I'd rather get a ignition coil from a car than buy a NST.

This site (http://amasci.com/weird/microwave/voltage2.html) is interesting too

[stupid939]

OK, I finished making the setup similar to N-P's, and it is running right now. I took a lot of pictures, and I will upload them to rapidshare or create a web page if someone would like them.

After I built it, I laid it out on the table, and I decided that it takes up way more space than it needs to. This is mainly due to the rigid, braided PVC tubing that I bought, because it does not alloy me to push everything together. I also do not want to stick the current set-up outside because I do not want it to get drenched and ruined in the rain (if I forget about it).

These reasons have all caused me to take on a similar project, but instead of spreading it out on a table, I will compact it into a small, box-like setup. I will have a roof to protect it from the rain, and when I want nitric acid, I can just flip on, let it run for a few days, and replace the jars.

One problem with my current setup is that the PVC reactor housing gets too hot after awhile, so I will switch to the terracotta pots and see how that works. Another problem is with my bubblers. I am currently using brass tubing to extend down into the water, and this may be a problem because it contains copper, zinc, and sometimes lead. These may lead to nitrates being formed, so I will need to switch to pvc or aluminum.

[stupid939]

Ok, I let my reactor run for about 12 hours and today I tried to neutralize a little bit of it (it was acidic to litmus). I tried barium carbonate and sodium bicarbonate, but the reaction was very slow, and I could only see a few CO2 bubbles.

I am remaking my reactor using all pvc and aluminum for the bubblers because the brass is not holding up too well, and I thought about something. Since the reactor works so slowly, could it be that the NO2 is not making its way to the bubblers as efficiently as it should? A quick check showed that at 21°C, NO2 has a specific gravity of 1.58. I do not know if this would affect the production that much, but would it help to move the "out" tube towards the bottom?

[megalomania]

Moving the air inlet to the top and the the exit tube to the bottom might not be a bad idea.

UV radiation emanating from the electric spark will decompose some of the NOx gasses. Considering how large the container is, and the likely flow rate of air from an aquarium pump, I would say the NOx gasses are exposed to UV for a significant period of time, especially if they are dense and tend to mix downward. Reversing the flow of gas such that the air that is exposed to the arc, and thus contains the NOx, is removed from exposure to UV light as rapidly as possibly should increase yields.

The formed NOx gasses are also heated longer if they must pass up into the container and then into the tubing connecting the bubblers. By forcing the gasses directly into the tubing and into the bubbler with the shortest delay you might avoid some decomp.

[Heat]

By the way, keep in mind that one way to increase yield is to use a DC arc under a magnetic field in order to spread the arc into an oval shape. To do that, you would build a simple 4 diode rectifier, and connect it to the output of your NST (or whatever you're using). And place two strong permanent magnets on both sides of the arc to create the magnetic field. This is what they did in the industrial reactors.

Oh, and I remembered the biggest problem I had when I had my reactor going: People coming to my house and saying "What is THAT?! What the hell are you doing?". Anybody else have this problem?

I can't just tell everybody that I'm making nitric acid, and no other explanation really works. I remember telling the stupid ones that I'm doing an experiment, and they would shut up. The slightly smarter ones, I made up something about generating NO2 gas for a study on air pollution.

Since I live in an apartment, I can't really hide it any more than putting it in a corner of my room. So any friends or family that come to my house will see it.

EDIT: I don't think that moving the air inlet to the top would be a good idea. I don't imagine the flow from an aquarium to be strong enough to overcome the hot air's tendency to stay at the top of the container. What I'd imagine happening would be that you'd have an accumulation of NO2 gas at the top of your container, which would slowly creep downward until it reached the exit tube at the bottom. So I think you would actually be exposing the gas to the UV light for much longer. Another problem is that the top of the container would get VERY hot. I remember that my exit tube (at the top) was very good at removing the hot air. If you put the exit tube at the top, the NO2-rich hot air would get sucked out of the container very quickly.

Another problem with NO2 accumulating in the container is that NO2-rich air cannot sustain an arc as well as normal air. (So the arc will go out.) Try it, set up a jacob's ladder under a jar. When the concentration of NO2 gets above a certain point, it will stop working.

[stupid939]

OK, well I thought about both sides of this (hot NO2 rising vs. the density of the NO2) and I am not quite sure which one would work the best.

I will use the setup that I am currently constructing and see how it works. It will have the desiccant chamber directly below the reactor, and it will pump (slowly) the air directly up, through the arc, and into the tube leading to the bubblers. The reactor will be constructed from two terracotta pots with holes on the top and bottom so that the air will make a path straight (hopefully) through the chamber. I hope that I explained this well enough, and if need be, I will provide a crude diagram.

BTW Heat, that is an interesting idea to spread the arc out. I may try it, if time allows, and report my results.

[megalomania]

Nitric-producer, in the close-up picture of your spark gap are those square things ceramic standoffs, or what?

[Darkover]

Just fyi, while Heat is right. It's not nearly so easy as put some diodes together. Your gonna need to find 4 scrap microwaves for there HV, 12kv+ diodes (or buy em, but I'm poor). Use corona dope or pot the diode bridge (again I'm poor, submerge the bridge in mineral or motor oil) to keep the spark from jumping between diodes.

[Nitric-producer]

I don't really think 12 hours is enough time of operation. It took me 3 days of straight running to produce about 1L of 50% acid. There are too many factors which cause the NO2 to "disappear". Until we work out the most efficient way of doing this, Im afraid your just going to have to leave it running a little longer :( .

Mega: After many failed attempts of producing a reliable spark, I made these "ceramic standoffs" ( as you refered to them). I had such a high voltage that occasionally the spark would jump onto the outside of the pot, and sometimes to ground (very scary). They are simply white plastic nuts. I made them from a chunk of heavy duty plastic and tapped them - so the electrodes would screw through! They turned out to be very good at holding a seal as well as being insulators.

[stupid939]

I am aware that running the reactor for 12 hours is not enough time to produce a very large amount of acid. I have to run it on and off because I do not want to leave it running while I am at work. Just in case something goes wrong, like tubing becoming corroded and slipping off, leaving the house to be filled with NO2 and NO. I also do not want to put it outside because it may get rained on.

I will have it run continuously when I finish my new setup, because it will be contained in its own little wooden house (it will even have a roof). I am working on the CAD drawings right now to get the layout how I want it, but it will come together soon. The reactor is almost complete, it is mounted on the desiccator, and the bubblers are done. While I am working on my project, you can see what kind of progress I am making. Some of the pictures have bad shadows because the lighting where I am constructing it sucks.

Current Setup 1 (http://www.free4up.com/ShowImage.aspx?fn=120027009164225.jpg)
Current Setup 2 (http://www.free4up.com/ShowImage.aspx?fn=093167177177175.jpg)
Current Setup 3 (http://www.free4up.com/ShowImage.aspx?fn=059195035206219.jpg)

New Assembly (http://www.free4up.com/ShowImage.aspx?fn=136206090231249.jpg) - This is basically my new setup. The NST and pump are not in there because they are being used.

Bubbler Pieces (http://www.free4up.com/ShowImage.aspx?fn=195155078066252.jpg) - This is what my bubbler is composed of. PVC and aluminum are the only materials that nitric acid will touch, with the exception of the teflon tape that seals the lid to the jar. The aluminum tube is pressed in on an arbor press, and is air tight.

Bubblers Assembled (http://www.free4up.com/ShowImage.aspx?fn=224148195128188.jpg) - Here are the assembled bubblers. After I glued them with the PVC cement (PVC resin dissolved in Acetone/MEK), I epoxied them for strength.

Desiccator and Reactor (http://www.free4up.com/ShowImage.aspx?fn=092085189248227.jpg) - As you can see, the desiccator bottle screws off for replacement, and there is a hole directly under the spark gap. The gap is not evenly spaced in the picture because one bolt it adjustable for the size of the spark gap.

Spark Gap (http://www.free4up.com/ShowImage.aspx?fn=079003151178071.jpg) - A close-up picture of the spark gap and the hole leading in from the desiccator.


The only thing that I am worried about is that the nitric acid may eventually attack the PVC resin (the cement) and then the epoxy. I may also end up putting in a acrylic window so that I can see into the reactor. It will make it a lot easier to adjust the gap.

BTW, On my reactor, I have noticed that the PVC near the top of the chamber has reddened and this tells me that the NO2 is, in fact, collecting at the top. There is also some slight leakage at the adjustable bolts, but that is nothing that a wrap with teflon tape wouldn't fix.

What do you all think?

[Alexires]

Not a bad set up Stupid939. Might I make a few suggestions? (I'm going to anyway)

In both setups, your reaction chamber is WAY too big. Think about how much NO2 can be contained in there compared to a chamber just big enough for the reaction. Looks like (just guessing) that your spark gap is about 10mm. Why not have that in a 15-20mm ceramic/plastic/whatever chamber instead of a pot. That way less exposure to UV light.

If you can't do that, consider getting a piece of stainless steel plate (only needs to be thin), drilling a few holes in it (just enough for the air to get through) and putting it over the top of the spark. Make sure it is insulated, and that is another way of preventing UV decomposition (not as good as the original).


Hot air rises and all that jazz. If you really wanted meaningful data to try and work out the spec. density of NO2 in the chamber, measure the temperature.

Let the fucker run for a few hours with the hoses and air pump/filters/blah connected and again for a few hours but with the reaction vessel fairly sealed (don't seal it tight otherwise you will have a problem with pressure build up). The temperature in the vessel with the pump attached is what I would call the "real" value and probably what the average specific density/temperature of the NO2 would be, but also take into consideration the temperature in the reaction vessel without air running through it. This will tell you what you might expect in "hot spots" or peak temperature.

I'm expecting the NO2 to rise out of the chamber, so you might as well have the air intake near the bottom and the vent at the top.

If you wanted to be really tricky, you could then pass the NO2 fumes from the reactor through a "condenser" set up. Maybe a PVC tube coiled in water with a few "baffels" in it to mix up the air as it goes through.

After this, you could pump the air into a cooled "settling chamber" where the (hopefully) cool NO2 fumes would sink to the bottom of the chamber. These are then passed through the water setup.

Remember, spheres (bubbles) have a shit Surface to Volume ratio. Either find a way to make smaller bubbles, or strech them out (another plate in the water to flatten the bubbles). Here are a few ideas for that.

When the bubbles are being pumped into the water chamber, have the chamer mostly full with a mechanical stirrer in there. Magnetic would be SO much easier for this.

As the bubbles come into the chamber, they are caught in the rotating water (thus breaking them up a little). On the outermost part of the water chamber, have a kind of mesh maybe, or a sheet of metal (verticle) with a few holes drilled in it. This will help to a) flatten the bubbles (increasing surface area to volume ratio) as well as b) break them up as they go through the holes. Just before the bubbles leave the first water chamber, have another sheet of metal (on the horizontal plane this time) with some holes drilled in it. Again the bubbles need to flatten out and increase the surface area.

Instead of this (if you're cheap, like me) you could fill the bottom of the water chamber with ceramic chips/glass chips/something non-reactive. Pump air into the bottom of that and as it rises, it will be mixed fairly well with the water and divided into smaller bubbles. You might have some trouble with all the water in between the chips have a higher HNO3 concentration than those outside the chips, but I doubt this will be an issue, or just fill the whole container with chips.

[stupid939]

Just what I expected to happen, did. While I was at work, I think my dog pulled on the tube leading out the door, and pulled the whole setup over. Both of the bubblers fell off of the table, and one tipped on its side. Luckily, everything is sealed, and it only pumped about 750ml of my ~2L out of the first bubbler. Everything is fine, and this just gives me one more reason to construct my outside reactor.

Alexires, you have some good ideas. I will design a reaction chamber in CAD, and I will post a few JPGs for everyone to look at. I will most likely construct it in the same manner, but I will use 3/4" or 1" PVC tube with at least one acrylic window. The nice thing about the reactor is that you can epoxy as many things as you want, and it is not affected by the NO2. I also considered plastic welding, but I figured that I may be able to do it with a modified soldering iron that blows hot air. Below is a link to a kit.

Plastic Welding Kit (http://www.malcom.com/products/pwk.php)

I could also make my own reactor out of anchoring cement, and it would be similar to the terracotta pots. This may or may not work, because I have not exposed the cement to nitric acid or NO2 (it seems to be fairly inert though).

If I use PVC, the only problem that I can see is that it may get to close to the arc, and possibly melt. I noticed that in my current reactor, the PVC softened up where the bolts touched it, yet the epoxy was fine. I will work on it and report back with updates.

I may also build an aluminum plate screen above the arc to prevent UV exposure. This would be fairly easy to incorporate into my smaller design, and it should take some of the heat off of the tube leading to the bubblers.

I have a hot plate/magnetic stirrer that would be perfect for the bubblers. The heating element went bad, and I can't find a close enough match for it, so I can't use it much for syntheses. I have some teflon stirring bars that would also be suitable, and I do not use them very often. I may just incorporate this into my new "house" design as an optional luxury.

[stupid939]

OK, I have been working on drawing my setup in Inventor for the last few days, and it is looking pretty good. Inventor does not have a good capturing program built in, so all of these are edited screenshots. Here they are:

Assembly - Isometric View (http://www.free4up.com/ShowImage.aspx?fn=201100168238038.bmp)

Another Full Isometric View (http://www.free4up.com/ShowImage.aspx?fn=229104049020143.bmp)


Assembly - Front View (http://www.free4up.com/ShowImage.aspx?fn=138177007217229.bmp)

Reactor and Desiccator (http://www.free4up.com/ShowImage.aspx?fn=110022178052092.bmp) (the desiccator is the bottle below the reactor chamber)


Reactor Cutout View (http://www.free4up.com/ShowImage.aspx?fn=015255082116249.bmp) (notice the aluminum screen to cut down on UV exposure)


Bubbler (http://www.free4up.com/ShowImage.aspx?fn=234013208135122.bmp) (The only thing nitric acid will touch will be PVC, aluminum, and glass)

I couldn't really draw the tubes, but I'm sure that you can understand how it works. The black thing in back on the bottom shelf is the NST, and the black thing in front is the pump. And above that, I even drew in the magnetic stirrer. I have everything built except the wood pieces, but that would not take long.

I would enclose all of this, and change the roof so that water would flow off of it, but this is the basic idea.

Suggestions?

[Alexires]

Stupid939 - Excellent work. I especially like your representation of the small grate/grill in the upper part of the reactor. Exactly what I imagined it to be. Maybe you could have a 90* piece on the PVC just before the grill there. Light travels in straight lines(ish), so any that does get through hopefully get stopped there.

The next step is to build it and see how it goes with temperature dissipation. You might want to think about having a kind of cooler/condenser set up running thorugh it just after the reaction chamber, otherwise you might have a problem with your water boiling in your collecter vessels.

Also, while in a pet shop the other day getting my water pump and air pump for this project, I espied one of those stone bubblers they have in aquariums. If it is resistant to acid/acid proof, it would be perfect to increase the surface area/volume ratio of our collection vessel.

If I remember correctly, gas solubility is the opposite of solid solubility. Eg. The lower the temperature of the liquid, the more gas you can get to dissolve in it. Henry's Law I believe. Hence, the colder we can get the water, the more NO2 we'll get dissolved in it.

Cooling will definately need to be a part of this experiment.

Looking at your design stupid, perhaps the reactor outlet can lead directly into a freezer where the tube circles a few time through acetone in there. Perhaps have a junction point that is metal to improve dissipation of heat and have the collection vessels in there as well. The only problem you might have with that is that the water in the vessels freeze, but if the air coming through was above 0*C (which I'm sure it will be) it probably wouldn't be a problem.

I expect that with everything stated above, you probably can make this for about $200-$300 (if you use an ignition coil instead of an NST).

You can get ignition coils cheap on ebay and find various plans to make a spark gap with them on the net. If someone with electrical know-how (I'm hopeless) could PM me in regards to making an ignition coil work for a spark gap, that would be great.

[jpsmith123]

I came across the following reference that makes me think it's possible, but I have no idea of the efficiency/practicality of the process. Maybe somebody can get the paper?

Nitric Oxide Formation by Ultrasound in Aqueous Solutions
Misik, Vladimir; Riesz, Peter
Radiation Biology Branch, National Cancer Institute, Bethesda, MD,
J. Phys. Chem. (1996), 100(45), 17986-17994

[stupid939]

I have been busy for the last few days, but I have some bad news about my latest design.

When I finished building it a few days ago, I put it together and let it run for about 20 minutes. I noticed that the bubblers were filling up with what looked like water vapor, but I could smell burnt PVC. If you looked closely at the exhaust, you could even see little puffs of smoke come out of it. Damn...

I guess that I will either make a similar chamber out of aluminum, or I will use a large reactor with a better design to cut down on NO2 breakdown. I may try the flowerpot reactor, because I know that it will work, but this really disappoints me. I based this design off of suggestions made by Alexires, so do you have any suggestions other than a cooling system. I don't think that the bolts and the chamber could be cooled fast enough to keep the PVC from burning.

[Darkover]

I've both magnetically ballasted a pair of MOT's and used an ignition coil. Believe me you don't want to use either. One very simple reason in both cases extensive wiring is needed and we’re talking voltages and currents way beyond what is needed to kill you with a single jolt. Anything much past 20kv will instantly paralyze you btw, meaning your ignition coil looks very cool but wired the wrong way or with the wrong parts and it is very lethal. A neon sign transformer is designed to produce the voltages needed at the required amperages and do so forever without overheating or shorting out. Ignition coil driver circuits need (usually) 12 to 30 volts DC at a few amps, so in addition to the crazy ball of wires and parts that’s hanging off the side of the coil you need a transformer and rectifier sitting beside them. A neon sign transformer can be had used from a lighting place in any major city for peanuts. By the time you’re done scrounging for parts and soldering everything together both of the alternative power supplies (if they haven’t killed you) will cost more than the used NST.

[Nitric-producer]

I am in the process of building a high voltage power supply using an ignition coil, just for fun :D .

Darkover: I can understand where you are coming from, but at the end of the day high voltage experimentation is always going to be dangerous. If you give it the correct respect it can be safe. It took me ages to track down my NST, mainly because everyone wanted it for experimenting! The parts to build my ignition coil, where bought for about $40. And I plan on enclosing it in a case with proper cooling. If you can get an NST easily, then I do however recommend it!

I will post back my results on using this power supply in the Nitric reactor.

[Darkover]

I take some of that back, I went to the usual watering hole for a NST and the prices have spiked, I picked up another 15kvolt nst but this one for 100 bucks. Still a good deal refirb in new condition, but not the 15 dollars I paid for his same era Allanson 12kvolt brother 2 weeks ago.

If you’re going for budget high volt power supply, use a TV fly back or an ignition coil. Stay away from a MOT controlling the raw current these will draw is difficult and dangerous for those who don't know how.

[Alexires]

Urgh. Sorry about that stupid, I was worried about something like that happening in regards to the PVC.

Is it burning where the bolts come through (contact), or is it burning worst near the spark all the way around and tapering off (radiation)?

Either way, you will either need to increase chamber size or use something that can take higher temperatures (like Al). An enlarged reactor will lead to decomp of NO2, so probably end up going aluminium, huh?

Again, sorry stupid. I haven't built one of these. I'm working on it, but I need to pick up a transformer to attach to my ignition coil. I am just expanding on your original set up. This is just an exercise in logic at the moment for me, until I get all the parts to start work.

I suppose the reason that we aren't using aluminium orignally is because of fear of hot nitric eating it away. Either try it with just Al, or you could actually heat the air coming in or Aluminium up. This way, even if there is moisture in the chamber, it won't matter as it won't condense on the sides.

If you are willing to give it a go, that would be great. Otherwise, you can wait for me to buy all the shit I need (probably a few weeks) and I'll do it.

Any other problems besides that?

PS. If you find that you still need PVC, you might be able to replace just the small holes where the bolts come through. Instead of just screwing them through the PVC, perhaps use something temperature resistant that is also a good insulator to screw the bolts into, and then this is screwed into the PVC.

This will only work if the burning is from contact though.....

[plutobound]

Maybe somebody can get the paper?

Nitric Oxide Formation by Ultrasound in Aqueous Solutions
Misik, Vladimir; Riesz, Peter
Radiation Biology Branch, National Cancer Institute, Bethesda, MD,
J. Phys. Chem. (1996), 100(45), 17986-17994

I downloaded a .pdf copy of it. I'll post it on rapidshare this evening.

[stupid939]

OK Alexires, I dissected the chamber and the burning was where the bolts contacted the PVC. There was also some burnt PVC above the holes, and because I only ran the reactor for about 20 minutes, I think that the chamber needs to be replaced anyways. I will try to make the reactor out of aluminum, and I think that it will turn out fairly well, especially because I can braze aluminum now (see my post in this thread (http://www.roguesci.org/theforum/showthread.php?t=4531&page=2)).

I would like to follow up on this project to be able to make nitric acid very cheaply, and also to contribute something more to this forum. I will follow a similar design using mainly aluminum, and I think that my dessicator should not leave any water vapor in the reactor, and like my first reactor, the chamber should be fine.

[Nitric-producer]

I apologise if this is a dumb question. However when reading up on simple transformers, it occured to me why not make our own step up transformers? Can anyone explain to me why you cannnot just build a simple step up transformer - and use it for high voltage experimentation? Sorry my knowledge on electronics is limited.

[Alexires]

Nitric-producer - I think you just stumbled upon why some of us buy it instead of making it - because we don't know how to make it.

Personally, I don't know a resistor from a brick. Certainly, if you had the knowledge of how to build it, you might as well do it (probably heaps cheaper), but for those of us that don't know and don't have the inclination to learn at the moment, best to buy the cheap parts. An ignition coil for $30, a variable step down transformer for the same and you are set....

Stupid939 - Again I apologize, I should have expected that to happen. You might have turned it of at the right time, any more and there might have been a case of PVC fire :eek: .

All the advice I can think of now is that it might be possible that whatever you use to weld the Al might not be resistant to NO2. Only really one way to find out. If it isn't resistant, you might get away with coating it with a 24hour 2-part epoxy (if it doesn't get too hot).

Also, your Al should hold up to NO2 if the air is dry. If you have something lying around that you can make cold (constantly), try putting that before the desiccator. The H2O in the air should condense on that and reduce the work the desiccator has to do.

Other than that, good luck and I look forward to hearing of your success.

[Darkover]

I've wrapped my own transformers. Couple reasons why buying is easier than making, imagine wrapping a wire the thickness of 10 human hairs around a metal core 10,000 times. Transformers like the type used in car audio to output power to cold cathode and electroluminescent wire have secondary wires the thickness of a human hair imagine breaking a wire on turn number 9,543 and having to start over.

The transformers I’ve done were all toroidal, that is, donut shaped. With a power supply like an NST the voltages require that the finished transformer be potted (submerged in a material of extremely high dielectric strength, under vacuum yet) otherwise the transformer may just arc within its own wires rather than where it’s supposed to go. It comes down to price, even at 100 dollars with the ability and experience to wrap my own NST the great lengths which a transformer like that needs buying it is cheaper.

For the curious a transformer is simply many wraps of one wire (the primary) and many more (step up), or many less (step down) of the secondary. Only ac voltage may be used in a transformer as it’s the (very simplified) push pull effect of ac voltage that magnetizes the core and makes the transformer work. Transformers with many more wires than the simple 4 have what’s called center taps, that is a wire is connected to say halfway along the secondary giving you half the voltage output of the secondary if needed. Computer power supplies and audio equipment do this very often. It allows a single 110v input to provide power at several voltages and amperages. NST do this on the secondary to limit the potential with respect to ground. Look on the side of your NST you should see a screw with no visible purpose just screwed into the side of the asphalt.

Confused yet ?

[plutobound]

I downloaded a .pdf copy of it. I'll post it on rapidshare this evening.

Sorry I'm a day late. Minor emergency. Here is the link to the article from the Journal of physical Chemistry:

http://rapidshare.com/files/29552933/jp961522x.pdf.html

[Heat]

Like I said, the heat from the arc is a real problem! You have to realize that we're talking about 3000 degrees Celsius. You can't just glue your electrodes to a plastic container.

What I did was suspend my electrodes in the air using copper wires. 15cm or so of wire is enough. I also wrapped copper wire around my electrodes to act as heat sinks and help cool them down.

I can't stress this enough: The arc is *very* hot; comparable to a small blowtorch. My container was about 30cm tall, and still the plastic and glue at the top couldn't take the heat. So I don't recommend a small container at all!

If you're worried about UV light destroying the NO2, you can try to put a few sheets of aluminum around and above the arc to block the light. Just don't get too close, since the arc will burn through aluminum. In the end, losing a little NO2 due to UV light is much better than losing your reactor due to heat.

By the way, I strongly advise against leaving your electrodes sticking out with no insulation.

[tareg_3d]

in this project Birkeland-Eyde reactor i need some explantion ,about the plasma arc .we know we have in the air netrogin andd oxygen and hydrogen .this acr it is inif to contact hydrogen with oxygen and i it can be do ,this water effect to electolet

[megalomania]

I just have a bit of pedantic foolishness I would like to get off my chest regarding the Birkeland-Eyde reactor. This is NOT the proper name to describe this particular method of generating nitrogen or nitric acid. In doing my formal writeup of this procedure I have acquired just about every book that has anything to do with nitric acid manufacture, including a rather complete history of the process.

More properly this should be called a Cavendish sparking apparatus, or a Cavendish reactor. Lord Cavendish was the first to pass electric sparks through air to produce nitrogen dioxide and nitric acid from 1781-1784. He developed the sparking apparatus, which is identical to the process we are using here.

The first nitric acid manufacturing process to take advantage of Cavendish’s experiments was an English patent in 1859 by one Madame Lefebre. Although this patent included specifications for a large scale manufacturing operation, electrical power generation was still too much in its infancy.

The first actual manufacturing process of nitric acid by the electric arc was the Atmospheric Products Company, in Jersey City, NY, run by Bradley and Lovejoy in 1902.

It was not until 1903 that Birkland and Eyde first began to develop their process, construction of the actual plant was a few years later, and it was quickly superseded by other electric arc operations. Every electric arc method was eventually doomed by the Haber process.

There you have a brief history of the production of nitric acid by electric arc, with the Cavendish reaction/method/reactor.

Now then, tareg, just rephrase your question in English and we may be able to help…

[nbk2000]

Looks like a machine translation to me. IP resolves to Germany, as I've been inviting people from a german forum here.

[Alexires]

Mega and NBK, I think that he is concerned as to whether H2O produced in the reaction (from atmospheric hydrogen and oxygen) would has some effect on the electronics? Perhaps the spark gap itself?

Tareg_3d - The amount of hydrogen in the air is 0.00005% as compared to nitrogen's 78% and oxygen's 21%. The amount of water produced as an unwanted byproduct would be so small and insignificant that it would have no effect on the outcome.

The spark gap would be so hot that water wouldn't precipitate on it, and other than that, your reaction should be sealed so that air pressure (used to push the NO2 gas through the water) wouldn't be lost. Anything condensing in the reactor during initial operation would evaporate as the temperature rose.

Fear not the horrors of Dihydrogen monoxide...

[megalomania]

Actually, with the presence of water vapor in the air due to the days humidity, and the long term use of this device pushing a rather large volume of air through it, there is the distinct possibility of nitric acid attacking metallic components.

This is why placing a desiccant bottle inline with the air flow, before entering the spark, can in all practicality eliminate this problem. As you may observe in the pictures stupid939 provided in post 123 ( http://roguesci.org/theforum/showpost.php?p=90105&postcount=123 ) he uses a mason jar. I myself use a large 3-quart pickle jar filled with calcium chloride with a length of glass tubing glued into the lid for the inlet, and a short bit of plastic hose barb glued in for the outlet.

[Alexires]

Megalomania, I made my post with stupid939's setup in mind, sorry if that was unclear.

Just curious, how often would your CaCl2 need to be changed (on average)?

[stupid939]

Sorry that I haven't posted my progress in awhile, but I had a little setback. Too much rain and no sump-pump caused my basement to flood. This included my shop and downstairs area, so it is a little hard to work until everything finds its rightful place again (it was in need of a cleaning anyways).

Just before the disaster, I finished most of my reactor made of mainly aluminum. I used homemade threaded teflon bushings to support the bolts. When I took temperature readings on my big reactor, I got a maximum of 180°C. Teflon has a melting point of 342°C, so I should be fine (side note - the ° is made by: alt + 0176). It looks pretty nice (except the fact that it is covered in epoxy), and I just need to finish up the inlet and outlet tubes. I will still put in a screen to cut down on UV breakdown, but I think that I will also put a bend in my tubing going out. I will attach pictures if anyone would like.

[Alexires]

Hit me with your pictures stupid939, I'm always eager.

Hopefully the teflon holds up. Spark gaps can get pretty hot....

[stupid939]

OK, I finally overcame my laziness and depression of my shop getting flooded and I took pictures of my new reactor. All of the joints are covered in epoxy because the Aluma-Weld stuff that I used left a few small leaks. There were also some leaks where the "bushings" slid into the aluminum tubing.

Top View (http://www.free4up.com/ShowImage.aspx?fn=095163160113158.jpg)

Isometric View (http://www.free4up.com/ShowImage.aspx?fn=078156014128150.jpg)

Side View (http://www.free4up.com/ShowImage.aspx?fn=115051205018164.jpg)

Another Top View (http://www.free4up.com/ShowImage.aspx?fn=157049201243134.jpg) - Notice the homemade PTFE "bushings/nuts"

Now I just have to make and fix a top and bottom to the body and it should be ready to use. OK, now it is suggestion time. I was thinking of a taller tube for the reactor body, and I want to use something else for the bushings, but it cant be conductive.

[Alexires]

Thanks for the pictures stupid. Looks like you go a little excited with the holes in the aluminium *grin*.

Next time you take a picture, would you be able to put a ruler next to it so we have an idea as to how big it is?

Looks quite exciting. That chamber is going to get hot, thinkest me. I think you might have some problem with the PTFE decomposing...

*sigh* What a pain in the arse. Perhaps we might need to change our approach in regards to the placement of the sparkgap. Instead of running it through the outside of the chamber, perhaps we need to have the leads running on the inside of the chamber but insulated?

What do you think stupid? Give it a test run and watch out for the flourine....:eek:

[nepsco1]

I have not been on in a while so I apologize for chiming in at this late date. I have some anecdotal information that may be helpful. I ran a DC Plasma Arc facility for several years with a Plasma Energy Corp. plasma torch operating at ~300kW, 400A, and a sinusoidal fluctuation of voltage from about 580 to 700 VDC. If we ran air as the plasma medium we created in excess of 100,000ppm of NOx in the reactor exit gas. (That was the limit of the analyzer, by a crude dilution I believe that the actual concentration was about 130,000ppm.) We scrubbed the gas with NaOH and water and created a solution containing high concentrations of both nitrite and nitrate.

Thus, the acids created on water contact were both nitrous and nitric. As I remember the break down in the reactor exit gas was ~60/40 NO to NO2.

The reactor was refractory lined and operated at ~1,200ºC.

This all could be mocked up using a welding shop plasma cutter and a small reactor lined with a cheap castable refractory with an insulating board layer between the refractory and the steel shell. If the plasma cutter is available, then the rector materials shouldn't cost more than $100 and could be a lot less.

I don't know if this is helpful, but I thought some of you may find it interesting.

[nightandday]

@stupid939

For sealing the electrode feedthrough, you can use gypsum. After solidification, drive out free water by heating to ~200 °C for 1 hour. When dry, gypsum is a good insulator and is heat resistant up to 800 °C.

[megalomania]

Hey, stupid939, don't they sell T or cross fittings where you come from? Wouldn't using one of those make life simpler and less epoxyified?

[atlas#11]

Microwave ovens all have a nice powerful ~2Kv transformer in them. The voltage isn't high enough to jump a great distance, but if your pumping air through it you should be able to rig something up.

I've had plans to do something like this for a long time, but never put any effort into it, I just cracked open my fourth oven this morning so I may give it a go. I've got plenty of transformers laying around from my Tesla coil experiments. If your looking to turn an ignition coil into a source you may want to learn how to make driver circuits for solid state Tesla coils, roughly the same thing.

Microwave transformers will draw a lot of juice and should be quite efficient at turning nitrogen and oxygen to nox, You'd probably have to pump quite a bit of air through it to keep it cool. I'm thinking I'll just go over to the art center and grab a big block of pottery clay to make the reactor and use some tungsten welding electrodes for the anode/cathode. Could make a nice weekend project.

[stupid939]

Mega - I am not sure where you can buy aluminum T or cross fittings. Copper may be usable, but I am not sure how it will react with NOx.

We do need to come up with a new design that will cut down on heat, UV exposure, and ease of construction. I may try the reactor that I just built, but it may take awhile because I still do not have much of a shop to work with (since the flood). An alternative that I mentioned earlier would be to construct it from a cement/ceramic material. Plaster of paris or Anchoring cement would be easy to cast with threading/electrodes incorporated into it.

[megalomania]

I was going to wait until I actually get the thing build, but I have a few tools for the project on backorder for a few weeks, so...

My design for the reactor will use fluorescent light bulb tubes. These bulbs are cheap, plentiful, and seemingly easy to work with. They are made of Pyrex glass, which enables them to withstand high temperatures, and being glass, are inert to chemicals and non-conductive.

The thinness of the glass should make them easier to handle, but mine is giving me trouble. I have all the parts I need, I just need to cut the glass to shape. Bottle cutters are expensive it seems, glass cutters do not work well on curved surfaces, wrapping the glass in string and setting it on fire does not give a very straight cut all the time... I spent a lot of time looking into DIY glass cutting over the last couple of weeks, there are many techniques, but I am going with the tried and true favorite, a diamond cutting tool.

Seeing as how I am cheap, or rather I want to stretch my limited funds, I ordered a kit containing a variety of diamond coated cutoff wheels and grinding tools for working with glass. The Dremel is my friend, yours too, but the cost of one bit at the big orange hardware store was only slightly less than a whole kit with several pieces. I just have to be willing to set aside instant gratification (I got the cheapest shipping, and I think it must be coming direct from Hong Kong).

Anyway, let me tell you my vision. The main reactor consists of a glass tube. The ends are capped with clay that is cut and molded to perfectly fit the ends of the tube. The clay is low temperature firing stuff that can cooked solid in the oven. I will mortar the clay ends on to the glass. By pressing the glass tube into a thick plug of clay I can create a good seal even before applying adhesive. The clay also allows me to mold a threaded nut and a hose barb into the material before firing. I found about 10 pounds of this clay while cleaning out something in the garage. How serendipitous.

I will fit two lengths of a threaded rod through the center nuts in the clay caps. These will help make the spark adjustable by moving the rods closer together or farther away as necessary. One of the threaded rods, the one opposite the inlet of air, will have a pair of nuts and a large washer attached to it. This metal shield fits inside the glass tube, but still allows the reacted air to flow around it at the edges. This is a UV shield that will block the light after the reaction is complete. This means I don't have to have some permanent screen fixed inside anywhere, it fits quite nicely within the tube.

The tube itself is placed inside a cheap semi-disposable plastic container. I cut round holes into the rectangular container so the tube just fits into them. The container is filled with cold water, and depending on how hot this water gets, I may hook my garden-hose-to-tubing-barb adapter, along with a pair of hose barbs for the container, to circulate a constant flow of cold water. The electrical contacts and air inlet/outlet never contact the water, the tube is submersed at all times, and I can still see inside the reactor and gauge the progress of the spark.

I hope I thought of everything... Go ahead, start your criticisms of my using a light bulb. And, yes, I did clean off the white stuff on the inside.

[Alexires]

Mega, If I may?

As I understand it, you have two nuts embedded in the clay which you will screw the threaded rods into. The will be both slightly off the vertical axis, allowing you to screw them in and out to adjust the spark gap. The large washer will be attached to the one afar from the air input and this washer will sit above the spark gap on the end of one thread (obviously threaded a few extra cm above the other rod to allow for this).

How were you planning to submerge it all in water? Were you going to just cover the clay end cap and all associate attachments with the epoxy god?

How are you going to pass the NOx fumes from the end of the pipe into your mother liqueur?

[stupid939]

I think that Mega was going to have the glass tube going through his water container, and have extra tube stick out of the container. The clay and electrode ends will then be out in the open so that he can adjust them. Here are a few sketches that I made (this is how I interpreted what Mega said).

Iso View (http://www.free4up.com/ShowImage.aspx?fn=026139010114212.bmp)

Front View (http://www.free4up.com/ShowImage.aspx?fn=005132087181202.bmp)

The large block is water, the tube going through it glass, etc. I think this would keep everything cool and it is a good idea. It is also cheap, but the only down side is that it requires a cooling system. How close to finishing are you Mega?

[in_flames]

Mega, assuming stupid's digram of your reactor was correct I have a few suggestions to make.

My first idea would be to cut the flourescent tube (if possible) into shorter lengths. I do not see any point of having a gigantic tube where the reaction is only taking place in a few cm. With that you could possibly even go without the washer as the clay cap is close to the arc blocking UV.

My second suggestion would be to make multiple of those small reactors placing them in parallel with eachother (assubing your power supply will allow for this). Thanks to your simple and small design I would say it is highly possible to integrate many reactor units into the one cooling tank.

My final suggestion would be to change the cooling tank to a flowing water system attached to a radiator and also cooling on the outlet pipe. Needing an extra pump would be an issue here but if its not too expensive I think it would enable the system to run much cooler encouraging NO2 formation.

Overall I think it is a good idea and if it works well I will be constructing something very similar.

[megalomania]

While I could not view stupid939's pictures, I think you guys have the gist of what I wanted to do. I cut a hole in the side of a plastic container, seal in the tube so that the ends stick out at either end, and I can manipulate the threaded rods to adjust the spark gap because it is not in any water.

Using multiple sparking tubes might be a good idea, especially if one wanted a higher production environment. I guess one of those very long but skinny plastic troughs you use when wallpapering would come in handy for that (these things allow a roll of wallpaper to be submerged in water, about 3 feet long, 6 inches wide, 6 inches deep, and dirt cheap). A parallel configuration would have the same voltage from your power source, of which a high voltage is needed to produce a spark, so only the current would divide with the addition of each apparatus. I don't know how a reduced current would affect the system, could be good for a few, bad for a lot. Anyone with electrical knowhow care to fill me in on that one?

There is no reason to have a long fluorescent tube, it only needs to be long enough to contain the spark. I wanted a longer tube to keep some of the heat away from the end plugs and the epoxied fittings therein. A longer tube should also facilitate better cooling of the inside air. I never really planned on building a million of these, so I have enough glass to last a while even using a long one.

The washer in the tube is entirely an optional feature. The total cost of the washer and the two nuts that hold it in place was 17 cents, so I was willing to splurge. This is a minor feature that may have only a marginal impact on yield, but for 17 cents there is nothing to lose by adding it. UV light does have some measurable impact on the decomposition of NO2 molecules, but it can also promote the oxidation of NO.

I won't speculate on a flowing water system until I see how hot mine actually runs. It will be simple enough to add if need be.

[stupid939]

I re-uploaded the files to a reliable site (imageshack). Sorry about that.

Iso View (http://img412.imageshack.us/img412/1908/iso1mn8.png)

Side View (http://img155.imageshack.us/img155/6879/frontmc3.png)

From what you further described, I feel that I accurately drew what you are building. I would agree with keeping the tube longer because of heat dissipation. I would also try to keep the diameter of the threaded rod as small as it can be while still being able to support itself and possibly a nut/washer assembly. I would think that this would keep the assembly as cool as possible. This assembly could also be built vertically to allow for small diameter rods.

Also, remember to seal the threaded rod with teflon tape. When I didn't, I could notice trace amounts of NO2 reacting with my epoxy.

I have not been able to work on this project lately because I have had to move everything around because of the flood. Now that everything is finding it's place, I will be working on and testing some designs. As usual, I will take pictures and share my experiences with all of you.

[Bodypain]

Few years a go i use Rumkorf coil, but there was only o3 not no2, there is another way like in circural welding use two graphite electrods, in this way dont need coil.

[ETCS (Ret)]

This discussion has grown greatly. My congratulations to those who are experimenting with the small scale production of a very useful material.

Much research has been done, particularly in Russia, on such small scale nitraters and the results are very encouraging. What you are seeking is definitely within your reach.

It is possible to obtain very high voltages with ordinary transformers. The key is to energize them with "non-sinusoidal" input pulses. This is how automotive ignition systems work and the voltage multiplication in an ignition coil so driven is many times the "turns ratio" increase that would be accomplished with a sinusoidal input - such as from the home power mains.

Due to the heat problems many of you have verified, and the need for keeping the reaction products sufficiently cool so as not to waste energy, pulsed high energy arcs are much more efficient. The continuous, low energy arc produced by the Neon Sign Transformer, while impressive in appearance, is very inefficient for the purposes you desire.

The high voltage output of whatever transformer system you use is best rectified with a high voltage diode string and applied to a high voltage capacitor to store enough energy to drive an intense high energy arc in very brief pulsations.

The diodes themselves need not carry a large amount of current as they will not be in the capacitor discharge path which sustains the arc briefly when the voltage has built up sufficiently.

The high voltage capacitors can easily by constructed and only about 40 Picofarads is sufficient at a voltage rating of about 50 Kilovolts.

An ignition coil system driven at several Kilohertz would be capable of producing high energy discharges at a rate of about two to three hundred per second.

The heat generated would be quickly dissipated in the normal air flow and the efficency of the process will be enhanced.

There is a trade-off however. The high energy discharges are noisy and may be an irritant for some. But, it is possible to design the system such that the noise is sufficiently attenuated, or muffled, so as not to be a great source of distraction.

May I encourage you to keep up the efforts?

In time you will find the secrets to good success.

[ETCS (Ret)]

In the above description I inadvertantly said two to three hundred discharges per second, when it should be per minute.

Two to three hundred discharges per second would be far too rapidly.

[jpsmith123]

Hello,

I'm wondering, can anyone get the following paper and upload it? Thanks.

Title: Nitrogen Fixation into HNO3 and HNO2 by Pulsed High Voltage Discharge
Author(s): Bian Wenjuan and Yin Xiangli
Publication date: June 2007
Volume: 9 Start page: 288
Publication: Plasma Science and Technology
URL: http://stacks.iop.org/1009-0630/9/288

Abstract:

Plasma processing induced by discharge offers a unique way to activate nitrogen molecules. Direct nitrogen fixation into water can be realized through this approach. In this study, air or pure nitrogen gas was used as the major nitrogen source bubbled into the discharge reactor. When a discharge occurred, nitrogen was dissociated to active species to take part in the aqueous chemical process. HNO3 and HNO2 were produced. The nitrogen fixation process was influenced distinctly by the presence of hydroxyl radicals. During a discharge of 21 min, HNO3 was the main product and occupied 95% of the total nitrogen content in water. Its concentration was 1.36 × 10-3 mol/L-1 with bubbling air and was 1.53 × 10-3 mol L-1 with bubbling nitrogen, while the yield was 2.32 × 10-8 mol J-1S-1 and 2.06 × 10-8 mol J-1S-1, respectively.

[megalomania]

I found two issues online in my journal center, but only up to Feb 2007. I thought it odd that there would be only 2 issues ending 8 months ago, so I checked a little deeper. It seems they were sent by accident, and the library does not have a license for them. Of course this does not help you, jpsmith123, but I tried.

The article sounds interesting, though, so I have requested it the long way. It will take a few weeks most likely.

[jpsmith123]

Thanks for your efforts, mega.

[Alexires]

Sorry jpsmith123, I tried to get it too with our subscription, but no go.

It is a new journal, and they don't seem to have a subscription to it yet. I tried to buy it, but not being a sheeple and owning a identity card (read credit card) makes these things difficult.

[black mamba]

jpsmith123 I believe this is what you're looking for. I just got access to this journal. If you need anything else, let me know.

[megalomania]

This is a very interesting article indeed. I especially like the simplicity of the design, acupuncture needles as electrodes inside capillary tubes as gas bubblers. If an American had written this experiment they probably would have had glass blowers build them a custom delivery system made of platinum costing thousands of dollars.

I am a little disappointed at the yield, but this is a small scale laboratory experiment, so it is not optimized for quantity production. I assume based on the abstract that their intent with conducting this research to begin with is to determine if it is economical to conduct this type of reaction. Certainly the conclusions of the article are not breakthrough, it has long been known that electricity air and water produce nitric acid.

The calculation of the rate of reaction seems to be the real heart of the paper. Using their calculations, a rate of formation of nitric acid of 2.06 x 10-8 mol J-1S-1 means a 100 watt system would produce 2.06 x 10-6 mol/S, or 7.416 x 10-3 mol/hour. It would take 134 hours of constant operation, for a 100W system, to produce 1 mol of nitric acid.

Since more wattage means more acid being produced per second, does anyone happen to know what a reasonable upper wattage limit would be for a improvised home based apparatus of this type? A 100W system should be obtainable at the low end, a system of several hundred watts, maybe even a few thousand could be doable, but I don’t have the electronics background to say how high one could “reasonably” expect to go. I say “reasonably” meaning using the kinds of electronics the average person can be expected to have on hand, or to acquire without much trouble or cost. I am also lowballing my estimates because there are many other cost factors involved here, the most significant of which is the energy used to distill the dilute acid.

A 562W system would be required to produce 1 mol of nitric acid every 24 hours. Also of concern is how concentrated the acid can get. I would expect some nitric decomposition at increasing concentrations. This system may only be feasible in producing nitrate solutions by periodically flushing the zapper water and neutralizing with an appropriate base (ammonia, sodium bicarbonate). At least it can produce nitrate salts from which nitric acid can then be obtained.

Assuming you do have a 562W system running for 24 hours, and assuming an electricity cost of $0.08 per kilowatt hour, it should cost you $1.08 to produce 1 mole of nitric acid. Factoring in 1 mol of nitric acid is 63.012 g, and pure nitric acid is 1.51 g/mL, then 1 L of 100% nitric acid would cost you about $23.96 in electricity. That’s comparable to what you could buy it from overpriced scammers, but I think industrially they can make nitric acid for about $1 per gallon.

[nbk2000]

It'd be worth $26/L to have NO ONE know you've got nitric acid. :)

[jpsmith123]

The apparatus is interesting as it seems relatively simple and compact (and BTW I fully agree with your assessment regarding the equipment implications of this work being done in a country other than the U.S. - I've made the same observation many times regarding the use of off-the-shelf materials and clever improvisation).

Anyway, the main value of this paper, IMHO, is the innovation of putting the HV discharge, air and water all in one spot.

As far as yield is concerned, it looks they didn't get around to trying to optimize anything yet, so it may be possible to improve the efficiency substantially.

Lastly, perhaps a neon sign transformer will work as-is for this application...there may be no need for spark gaps, pulsing, rectification, etc.

[megalomania]

I have been briefly reading up on the rotating spark gap they mentioned, that might be a useful thing to use to increase the life span of electrodes. As for the yield, two things occur to me. First, since this is a pulsed system it is not continuously operating, so the energy usage might be substantially lower. That’s probably why they calculated their yield in joules. Second, given the small volume of the reactor (100 mL) yields of a larger system would likely be much greater. A higher voltage should produce longer sparks, which in turn should lead to greater yields.

Now here is a system that could benefit from the Nafion nitric acid concentration method. Make up water could be slowly added to the reactor causing the dilute nitric acid to overflow into a water tank. A coil of Nafion tubing, or another suitable water permeable membrane, is immersed in the acid solution. The air for the capillary bubblers is blown through this tubing pushing wet air back into the reactor.

A low powered lab scale system could conceivably remove enough moisture from the nitric acid reservoir that it becomes its own source of make up water. A suitably inexpensive length of Nafion tubing would be measured to remove sufficient moisture approximately equal to the rate of nitric production. The reservoir acts as a cooling system as well, as the warm overflow water trickles into the large reservoir it cools to room temperature, and the cooled moist air inside the Nafion tube acts as the main source of cooling for the reactor. Evaporation of nitric acid could become a problem at higher concentrations unless the reservoir is sealed.

With nothing but an air pump and a neon sign transformer as the big equipment, and electricity, air, and water as the reactants, the system I just described could eventually produce 75-80% nitric acid on a continual basis. The rate of acid production would depend only on the scale of the device. Conceivably, experimenters could produce sufficient nitric acid for basic lab work, small scale experiments, and chemical tests using only a small scale system. Those desiring greater quantities of acid would have to invest in a much larger system, but I think this could be at least be divided into multiple systems using multiple transformers if a gigantic single system is impractical (multiple reactors in parallel with a common reservoir using inexpensive surplus transformers vs. an exponentially more expensive single system with an industrial transformer).

It is well worth it to have a means of producing nitric acid independent of fedgov regulation. Factoring in shipping and handling costs of acid shipments alone, which greatly exceed $26 per liter, and you are already ahead of the game. A large manufacturer might not benefit from this technology, but it is economically feasible for the small scale producer.

[gaussincarnate]

This is a little off-topic, but this is the most relevant thread that I could find. If nitric acid is produced commercially via the oxidation of ammonia at 850 degrees C (or thereabouts) with a platinum gauze catalyst, then would it be possible to produce nitric acid in a somewhat related manor (via oxidation)? I was wondering if electrolysis of a water/ammonia solution would form nitric acid, since water will break down before ammonia, releasing oxygen and hydrogen and hopefully oxidising the ammonia in turn. I think that it may have to be carried out at a higher temperature to encourage the oxygen to react instead of just bubble out. I used the search engine and meandered about the internet for some time, but I could not find anything on this process. I hope that means that it is not used often and not that it does not exist, but there is only one way to find out. I was just wondering if anyone has ever heard of this before, if anyone has ever tried it, or if anyone thinks that it might (or might not) work. Thank you.

[megalomania]

Electrolysis of a water and ammonia solution would produce hydrogen and oxygen. If you are lucky, you will decompose your ammonia as well. Any nitric acid that did form, and it would be a very small quantity, would react with the excess ammonia to produce ammonium nitrate.

A higher temperature would only serve to vaporize the ammonia in solution, which has a rather low solubility in hot water.

Again, I am not saying you can't make nitric acid this way, just that you will have a virtually nonexistent yield. Unless you employ some rather fancy solvents or exotic setup, no nitric this way. Don't take my word for it though, if there is a method to do this, you would be most likely to find it by checking the US patent database for ammonia electrolysis (freepatentsonline.com).

What you can do is electrolyze nitrate salts in a divided cell to obtain nitric acid and alkali hydroxides. This is probably a lot more trouble than it is worth considering you can do the same thing by heating the salt with sulfuric acid. If you can go through all the trouble and expense of setting up a divided cell electrolysis, you can get sulfuric acid and glass distillation equipment.

[ProdigyChild]

I've been playing with pulsed power quite a lot, recently. Thanks to wind power plants and hybrid cars, extremely rugged electronic devices have become affordable to the home experimenter: IGBTs.
I've build a ferrite rod core transformer, that can produce peaks of up to 60kV, 20us, exponential decay. Not that impressing, you'd say. Right, but:

The transformer can be build easily: single layer of wire on cardboard tube (toilet paper)
No insulation problems, because it's 30cm long
Easy power dissipation
Not too much windings, only a few hundreds, single layer
Only a few Ohms of DC impedance
The core can be built from ferrite torroids or other cores by stacking
Secondary output ist still a few amperes peak.


The major drawback is the electronic part. To get 100..200V of voltage per winding, you have to switch about 1000V at 500..1000A at the primary side. This is, where the modern IGBTs come in. 1200V/800A device can be obtained for about 60$ from EBAY. Driving these parts isn't too easily, but I could provide a schematic and layout. It can be powered by 12V or 24V

This approach gives me the freedom to build HV-pulse-generators accoriding to my specification. However, I can't produce DC with that.

I wonder, if this device produce NO3- in the way described above. I should check that.

At least, it can act as the ignition part of a high power arc, directly powered from the 230V line. I can't run that beast for more than a few seconds, without well venting the room (NOx) :D

[nightandday]

You don´t need such efforts. Microwave oven transformers (MOT) are best suited to build up power supplies for driving electric arc furnaces.

Two MOTs should be connected in series on primary and secondary sides, to reduce current and avoid overheating. Use 3 or better 4 such pairs parallel. Then you will have enough power (2000 V and 2 A). So, the first thing to do is to collect MOTs from old microwave ovens. 12 MOT´s are sufficient, 16 are better.

[megalomania]

Some months ago I learned the lifetime of transformers quickly degrades when used for long periods of time in the type of usage making nitric acid would entail. This means you will likely need a constant infusion of transformers even for casual production of nitric acid. I have been trying for months to get my hands on microwave ovens of any stripe, and I only have a few. Only a very few people could reasonably expect to scrounge enough electronic parts, and they are likely well connected to electronics sources already.

ProdigyChild seems to offer a preferable alternative by using an inexpensively made sacrificial transformer made from other robust components. I don't know that much electronics, but I gather an IGBT should last for quite some time.

nightandday's suggestion of multiple transformers in parallel might also alleviate premature transformer degradation. It is unnecessary, and probably unsafe, to have higher amps. The voltage should be quite high only to initiate a spark, and the current be minimized to reduce the cost of operating the device.

Ideally I would think producing as long of a spark as possible using as little energy as possible would maximize NO production per dollar spent.

[ETCS (Ret)]

The Microwave Oven Transformers as sources of the high voltage are promising. In fact just one with a sufficient number of voltage multiplier stages (diodes and capacitors) would be able to generate enough stored energy to produce a 20KV or more pulsing arc.

If the primary of the Microwave Oven Transformer were driven electronically with a capacitive discharge circuit of 300 volts by means of a Thyristor, then the pulsed output voltage at the secondary would be in the vicinity of 10KV or more before multiplication.

The historic Nitrogen Fixation Processes using the electric arc are:

Birkeland-Eyde process (1905) successfully implemented in Norway used water cooled electrodes with a magnetic control field at D.C. 5000 Volts, 200 Amperes.

Bradley and Lovejoy process (1902-1904) implemented briefly at Niagara Falls used a rotating hub with spikes style electrode that produced 9,250 arcs per second at D.C. 8000 Volts, 750 Milliamperes.

During the time those processes were in successful use the efficiencies were limited by the thinking, electrical capabilites and knowledge of the period. Modern research and trials have produced Electrical Nitrogen Fixation processes which are more efficient but still not competetive with the ammonia process for industrial scale production. However on a small scale for modest production they are very attractive.

The modern processes are based upon the Nitrogen Fixing power of lightning and have shown that very brief high current electrical discharges through air are very effective.

The electrical energy is stored in high voltage capacitors, then the high voltage discharge into air is either stimulated or allowed to occur spontaneously in a repetetive manner.

A very interesting and enlightening paper on the chemistry of lightning produced Nitrogen Oxides is the Yujin Wang Thesis.

[ProdigyChild]

I'm itching to read the pdf ETCS provides, which is awaiting approval at the time of my writing.

Thanks Mega, for clarifying what I failed to communicate clearly: The aim is to build an arc generator that's easy to build from easily available components and that does not suffer of degradation.

Right at the moment I'm addressing the problem of how to reduce the electrode wear. We all know, that needle-shaped electrodes perform very well in terms of igniting a long arc. However they're vaporized in the twinkling of an eye if loaded with a current (pulse) that can produce noticeable amounts of NO. That's why I use rather smoothly shaped electrodes. I put up with the fact I have to use extreme voltage to ionize the air. But with these electrodes I still have considerable wear, mostly (I hope) because I'm using a rectifier/capacitor/inductor-circuit to limit the power drawn from the 230V power line. This construction results in short pulses of 1-2ms of current at about 50A at a repetition rate of 50Hz. I hope, I can reduce the sputtering of the electrodes by using a switch mode electronic regulator to limit peak current. More precisely: to SHAPE the arc current to whatever turns out to be the best compromise between electrode wear, efficiency and speed.

The Jacobs-ladder approach can be applied to my system, too, although in a slightly different way: if a strong magnetic field is applied at the arc's location, then an arc that normally looks like ball of 8mm in diameter is spread out on bent area of estimated 2cm^2. This improves electrode durability and probably efficiency. I hope this is still applicable, when I reduce the peak current.

[megalomania]

ProdigyChild, do you have and published material or advise to pass along concerning the magnetic spreading of the arc? I searched for this some last summer, but I didn't find much since I am not exactly sure where to begin or search terms to use.

The greater the volume of the arc, the more NOx gets produced. I found the theory, but I could find any information on how to use a magnet to spread an arc. The theory is nice, it seems very sound, but where are the practical details, the how-to, and applications of the theory?

Since I am really unsure as to how I could test the spread of the arc, how am I supposed to tell if just sticking some magnets near the electrodes works or not? I highly doubt it is that easy...

Indeed the ammonia route (Haber process) is more efficient, but the start up costs for all the specialized equipment is very prohibitive. If you have anything less than extreme high pressure tanks, furnaces, syn gas production, hydrogen and nitrogen reclamators, ammonia liquefiers, etc., you will waste a lot of money. Can all this equipment be made on a small scale? Not without a very significant investment of money and materials. The electric arc route wins hands down on the small scale because it uses cheap readily available materials.

What's your option, do it yourself and gripe about spending a few cents extra per liter of acid compared to what it costs industry, or spend 1000x what it costs and have some chemical supplier ship your acid?

[ETCS (Ret)]

The Yujin Wang Thesis can be downloaded here:

http://www.ireap.umd.edu/ireap/theses/YujinWangThesis.pdf

It took me a little digging to find the URL for the download, but fortunately, it was still on the list.

[ProdigyChild]

Takes some time to read the Thesis. I wonder, what electrodes they uses to discharge a 1000uF Capacitor @ 10kV :eek:

@Megalomania: No, I don't have much published material. What I know comes from much experimenting and some reading about HID lamps. High pressure sodium vapor lamps raised my interest recently because the have up to 140 lm/W, while LED's are still below 100lm/W.
Spreading an arc is really as simple as putting a medium strong magnet below the arc. If the north pole is on top and the south pole on the bottom and the arc is in the middle of the magnets pole, then the arc will spread horizontally. Same is true if you exchange north and south or invert the current flow. The effect is pretty strong. You don't need that neodym style of magnet.

Todays activities:
I have a prototype running, and made a few experiments. Let me describe the setup a little bit. It consists of 2 parts: the ignition circuit and the main power supply circuit.

The ignition circuit is connected in series with the main power supply circuit and strikes through the air 50 times per second, when I press a button. It creates a 0.5-1mm thin 'thread' of ionized air. I use at most 0.1J for this on the primary side of the HV transformer. No idea how much I have left of it on the secondary side. It's basically discharging a 220nF capacitor (FKP1) charged to 600..1000V over the primary of the transformer.

The main power supply is a 'step down' 'buck' topology constant current regulator. Key parts for those who care: UC3845, IRF840, DSEK60-06, 6.8mH coil. I use a rather low switching frequency at the moment, because I want that toy to withstand short circuit for a long time. What is does! :D
If no load is present, the voltage rises to 320V. If I short it, the the voltage drops to zero, while the adjusted current is maintained. When I open the short, a massive arc appears. The current can be adjusted from zero to 5A at the moment. Shorting the supply isn't spectacular at all, since it's output is mainly inductive, only 150nF of capacitance in parallel. Although the analog input would allow current shaping, I only switch constant current on or off.

So, what have I found so far?

a) I cannot keep a low current (e.g. 0.5A) arc burning. I have to use 3A or more to reach a length around 10mm. I'm a bit disappointed about that.

b) Similar problem: In a setup, where I can strike through 20mm of air with the ignition circuit, I can keep the main arc burning only up to 10mm. The main arc does not appear at all! (I believe, it's roughly the same arc length I can reach, when shorting the power supply and then slowly pulling apart the electrode bars). Increasing the maximum current helps a little bit, so does using more energy for pre-ionization.

c) Spreading the arc with a magnetic field is counter-productive in terms of stable arc length. A strong magnetic field can reduce the maximum arc length to nearly zero. :eek:

d) I have the impression that steel electrodes allow much longer arcs than copper ones. I should examine using electrodes of the same shape and size and only different in material. I do not use Tungsten electrodes although I have some. NO2 can be removed by venting the lab, Tungsten dust can't.

e) The good news is: I definitely have much less electrode wear, although still far from an acceptable level.

Experiment details and calculations:
1) Ignition transformer secondary coil: 0.8Ohms (DC), wire diameter 1.0mm, 200turns, coil length 220mm, diameter 44mm; reliable arc-over (ignition) about 8mm.
At an electrode distance of 8mm and a current of 5A I read 50V of arc voltage. Reducing the current to 2A results in 70V arc voltage and somewhat unreliable ignition. The power released is roughly 250W in the first case, 140W in the second. Power dissipation of the coil is 20W and 3.2W respectively.

2) Ignition transformer secondary coil: 15Ohms (DC), wire diameter 0.4mm, 500turns, coil length 220mm, diameter 44mm; reliable arc-over (ignition) about 20mm.
At an electrode distance of 9.5mm and a current of 2A I read 90V of arc voltage. At 3A I read 85V arc voltage. The power released is 180W in the first case, 255W in the second. However, the high DC resitance of the coil eats up 60W and 135W.


The measurements show, how difficult it is to release power into the air, rather than into the the equipment. It's remarkable, how low the arc voltage is. It's surprising to me that I can't stretch the arc longer. Perhaps it's because my circuit isn't ideal - it presents a positive resistance to the output.
The current is not that constant. Apart from that I can see, that the arc is really hot and the air flows upwards and extinguishes the arc. When I arrange the electrodes vertically I can indeed get considerable longer arcs. Of course, all the hot air hits the upper electrode then with obvious consequences...

Any suggestions about extending electrode lifetime?

[ETCS (Ret)]

In order to minimize the large power losses as heat it is necessary to use a stored energy discharge system of pulses. The electrical process of charging the high voltage capacitor with a relatively low current will be quite efficient.

When the voltage becomes high enough to arc across the electrodes (selt-initiated) the discharge current will be very high and very brief. This generates a huge instantaneous power and very high temperature to form the nitrogen oxides and ozone, and because of its brevity allows for rapid cooling of the gasses to preserve the oxides before they decompose.

The pulsed discharges will greatly prolong the life of your electrodes since they won't be overheated by a continuous arc.

You'll find a great deal of useful info in Yujin Wang's extensive tests and analysis.

[megalomania]

I read somewhere that using spinning metal disks as electrodes reduces wear because the hot arc only contacts a point on the metal briefly. This is one of the reasons I incorporated a steel washer into my glass tube reactor design. Rotary spark gap is the proper term for this I believe.

[ETCS (Ret)]

The high powered Tesla Coils built by Tesla Experimenters still use the "Disruptive Discharge" method Tesla used to feed the primary winding.

There are several very good Tesla Coil websites that go into good depth on the construction of durable spark gaps, and some of them explain the use magnetic field quenching to control the discharge.

When you find one of the Tesla Coil sites via search engine, it will have links to several others. They're a very supportive and cooperative community, not to mention very capable technically.

You'll find a lot of very helpful info.

[ProdigyChild]

I've read parts of Yujin Wang's thesis. Really impressing, lots of ideas that will help me!

But I'm a bit disappointed that he reached only 4cm main arc length, even though the Marx-generator could strike through 20cm? An why the hell wait for 80us after the Marx-generator triggered? Probably this is the reason. Or the cascading of 2 spark gaps (main arc+SF6 triggered gap).
If I can get nearly 1cm with 320V he should be able to ignite a main arc of over 10cm I would say. Give me that capacitor bank, I'll have a try! ;)

I've thought about my limited current approach and I fear it's a nice experiment but not efficient in the end. A better approach could be to ionize the air and then send a burst of medium current pulses - say 20A - through the channel. The time between two pulses tweaked to let the air cool down a little bit so that the next pulse has a large voltage drop again. That way I could transfer much more heat to the air.

A disc electrode need not rotate all the time. If the rotation is an oscillation only, you still have the benefit of a better distribution of stress. Such an oscillation can be excited by a coil from outside the reaction vessel. No trouble with sealing, wiring or motor corrosion.

[ProdigyChild]

Hi all, I want to provide a photographs of the arc under the influence of the magnetic field.

1. photo
I placed a strong N52 magnet at 7cm below the arc. The image was made by exposing for about 1s at daylight with tiny aperture and switching on the arcs repetitive ignition for as short as I could do by hand.

2. photo
Same as above but magnet removed. Also there's no chance to have a short period arc as it does not quench any more without the magnetic field. This image gives you an idea on the size of the arc without B-field.

[Updated:]
3. photo
Now using electrodes arranged like a Jacobs ladder. On the bottom you can see the N52 magnet again. Again a long term exposure.
The arc lives for about 1second and travels in that time from bottom to top. The initial few cm are heavily accelerated by the magnetic field. Otherwise it would stay at the bottom and melt down the electrodes. The arc you see uses no more than 200V after ionization.

Holy shit! I can't write down all that comes to my mind right now. I think about using an array of magnets all along the electrodes to speed up the travel of the arc.
I also wonder if the arc would leap over a gap. Over to another pair of electrodes of low voltage (100V?) but obscenely high current easily controllable by a few power MOSFETs. The more current the stronger the propulsion of the arc in a magnetic field - we could accelerate the arc like a projectile of a rail gun! This propulsion could be used to let the arc travel through the air at enormous speed and leave behind a low pressure area that 'freezes out' the NO as described in the thesis pdf. Finally fresh air is sucked in again and we give it another high energy flash!

I stronly believe, that modern electronics has just given us the tools to produce NOx with an ease and efficiency not imaginabe before!
[OMG this sounds like the words of a politican...]

[Updated again:]
Yes, the arc can leap over a gap!
I placed a 500uF capacitor charged to 300V on to of the arc shown on photo 3. It discharged with a loud bang, i.e. the inductance of the transformer coil was skipped and the arc found a ultra-low impedance current path. I have to check the reliability of such a leap over a gap of course. In case of success, I need to shorten the Jacobs-ladder setup shown on photo 3 and optimze it to a plasma 'gun'. This plasma gun can then be used to inject ions between the rails-electrodes of a high current arc. The high current arc supply does not need to be able to produce thousands of volts any more - this makes the design much easier. High impedance coils can be omitted allowing for extremely efficient power conversion from AC line to the arc and for MUCH higher currents at even lower power dissipation.

Another experiment to carry out soon will be the measurement of the arc's traveling speed at the lower end. At the lower end its considerably faster than at the upper part.

[nightandday]

If you use it right, MOTs are well suited to build up power supplies for elecric arc furnaces.

MOTs used in general type microwave ovens (not inverter type) are single-phase dry-type transformers with iron-cores and copper coils, designed to operate at 50 - 60 Hz.

Here are some technical data of a typical MOT (from Microwave oven 230 V~, Input: 1150 W, output: 700 W):

weight: 3.2 kg
transformation ratio: 10
ohmic resistance of primary coil: 3,0 Ohm
ohmic resistance of secondary coil: 250 Ohm
reactance of primary coil: 1.5 Henry
reactance of secondary coil: 65 Henry
nominal voltage: 170 V~
rated power: 300 VA (derived from weight)

At 230 V~ primary voltage:

no-load loss: 75 W
no-load primary current: 2.1 A
secondary voltage: 2.1 kV
short circuit current (secondary): 1.7 A


At 115 V~ primary voltage:

no-load loss: 15 W
no-load primary current: 0.26 A
secondary voltage: 1.16 kV
short circuit current (secondary): 0.93 A

MOTs in microwave ovens are overboosted. This is only possible for short periods of time and with forced cooling. For continuous operation of MOTs, primary voltage must be < 170 V~ and output power < 300 W or secondary current < 300 mA.


This arrangement of MOTs is good enough as continuous power supply for electric arc flames.

http://rapidshare.com/files/95715669/MOT_Batterie.pdf.html


Note: reactance is required in the circuits of an arc furnace to give stability and to limit the current. Using DC, an ohmic resistance (e.g. 500 W Halogen lamps in serial and parallel connection) is required, causing heat losses.

[nightandday]

The dissertation by Yujin Wang (University of Maryland) gives the following information about the NO yield of laboratory sparks.

"... studies ... reported ...the number of NO molecules per unit of discharge energy ... as 2 to 17*10^16 NO/J" (p.8)

"... the NO yield of a lightning stroke is usually determined by two parameters: the NO mixing ratio when NO is "frozen out" from a spark channel and the amount of air mixture involved." (p.90)

"...correlation between NO production and spark energy is very complicated..." (p.91)

"The observed pNO (NO production per unit energy) is greater than the previously reported results of simulations or observations in laboratory sparks. ... The pNO by a simulated spark with peak current of 30 kA ... is 40*10^16 NO/Joule in our experiments. This discrepancy of the pNO values may be caused by the different energy accounting used in our results. In most previously reported works, the stored energy was used as the energy to calculate NO... In our experiments, only the energy dissipated in a spark was used as the the energy to produce NO. The diagnostics of experimental sparks ... has showed that less than 1% of the energy stored in the capacitor bank was dissipated in the discharge channel. If this stored energy was accounted as the energy to produce NO, pNO would be 0.15 - 0.30*10^16 NO/Joule ..." (p.92)

"...water has little effect on NOx production..." (p.94)


Notes:

Conversion: 10^16 NO/J is equivalent to 3.77 g HNO3/kWh. (1 kWh = 3.6 MJ)

The maximum yield reported for sparks in air is 17*10^16 NO/J. (Chameides, Nature 280, p.820)
This corresponds to 64 g HNO3/kWh.

The maximum yield reported by Wang is 0.3*10^16 NO/J (with respect to real input energy stored in the capacitor bank), which gives only 1.13 g HNO3/kWh.


For comparison:

The reported yield of Schoenherr reactors (using a single arc flame in a long vertical tube without magnetic field) is more than 80 g HNO3/kWh (best values are about 100 g HNO3/kWh).

The Birkeland-Eyde reactor is more complicated and less effective:
"... the yield was between 500 and 600 kilogrammes of anhydrous nitric acid per kilowatt-year". (i.e. 57.0 - 68.4 g HNO3/kWh)
K.Birkeland, Proc. Faraday Soc. VolII-T5, p.108 (1906)

[ProdigyChild]

I've tried to build a suitable reactor. For the first try, I used a cylindric glass of 10cm diameter, 22cm length. For the electrodes I used copper pipe, 8mm diameter, 20cm length. To get the vessel sealed, I used a PCB-board with 2 separate areas of copper. Through each of the areas a 8mm hole was drilled, an electrode tube put through it and finally the tube was soldered to the copper area. The copper area serves as current connection. The class vessel is put onto the PCB-board with the electrodes sticking 18cm into the cavity to the vessel. As the electrodes are tubes air can be pumped into one of them and sucked off the other. This serves both gas throughput and cooling.
I'm really convinced that using a magnet to move the arc is the way to go. So I'm using a STRONG magnet like in photo 3 of my previous posts to accelerate and guide the arc all the way along the electrodes. This can be done from outside the reactor. On the last 2.5cm the electrodes are kinked outward so that their distance increases to 3cm and the arc is quenched there. The shortest distance between the electrodes is 3mm and I must tell you this is still too much for reliable ignition with the current circuitry! The smooth surface of the electrodes makes it much more difficult to ignite the main arc even though the preionization arc strikes reliably. Even worse after maybe 20seconds of accumulated use of the first run the main arc refused to ignite at all!
I hople I can get over these problems by welding a small pin to the electrodes the make them ignite more easily.
From direct measurement of arc voltage and current I have to assume that up to 900W will be released inside the vessel thanks to the magnetic spreading of the arc :)
The total area the arc travels through is approx 7cm2. Not that bad, really.

Does anyone know if silicone rubber will withstand NOx so I can use it on the outlet of the reactor?
What kind of materials do you suggest at all?
Someone (nightandday I believe) proposed gypsum for fitting electrodes.
Is there a nonconductive nonvolatile liquid I could use to submerge the lower end of the reactor to have no NOx escape into my room? Destilled water has for too high conductivity for the high voltages used, unfortulately.

[ETCS (Ret)]

Good points.

It seems Wang was trying, on a small scale, to duplicate the current densities of lightning discharges, which are enormous. Lightning itself is not particularly efficient, by apparent design, because of the great excess of overcurrent.

The description I have of the Schoenherr reactors is that of a "long filament arc of low intensity through the tube," which, coupled with optimal airflow, probably produced the higher efficiency.

The setup can be "tuned" for greatest efficiency by limiting the stored energy, and therefore the current intensity of the discharge, to minimize losses associated with excess current flow produced heat, thus enabling more of the oxides to survive.

Interestingly, other studies have shown that Nitrogen alone, by electrical discharge, may be made to react with water to produce Nitric Acid.

Many fascinating possibilities spring to mind.

[megalomania]

I have never heard of the Schoenherr furnace until now. After a little research this apparatus sounds very similar to the setup used in US patent 4877589, Nitrogen fixation by electric arc and catalyst, that I want to build. The patent incorporates a tangentially added air tube that doubles as the holders for the electrodes. The air is circulated in a vertical chamber filled with tungsten catalyst coated alumina spheres. The air passes directly over the electric arc as it enters the reaction tube.

The Schoenherr furnace seems to be a vertical iron tube, a pipe most likely, with a central electrode in the middle along the entire length. The spark spirals up the electrode like a Jacobs ladder while air is inserted tangentially.

Adding the air at a tangent creates a vortex like effect (tornado) that circulates it more, increasing the likelihood that something will contact the electric arc, and this fast moving air will have a limited contact time. The longer the contact time the great the possibility of your nitrogen oxide decomposing back to nitrogen and oxygen.

I found this nice google book that had a chapter about electric furnaces, including a section devoted to nitrogen fixation furnaces. Electrician's Handy Book: A Modern Book of Reference by Thomas O'Conor Sloane is available in its entirety from google at http://books.google.com/books/pdf/Electrician_s_Handy_Book.pdf?id=SvUOAAAAYAAJ&output=pdf&sig=iA9DeCfWCZ-NoQCuGoD1Xlo6rzY

This book just makes the cutoff for public domain works it seems. I have attached the relevant pages about nitrogen fixation furnaces, pages 782-786.

This book reports the yields of nitric acid for the Schoenherr furnace at 65g/kWh, and for the Brickland Eyde (their spelling) at 67-70g/kWh.

I did see a study (I probably have it in my folder of nitric acid files somewhere) about producing nitric acid from an underwater electric arc with nitrogen gas being bubbled in. I forget what the conclusions were of this reaction.

[jpsmith123]

The process described in the paper by WENJUAN et al. (using HV pulses in water) has apparently been patented (or is in the process of being patented) in China...so the inventors and their sponsor must think it has some commercial potential. Here's the abstract from the European patent office:

Abstract of CN1903705
The present invention discloses a method for making nitrogen fixation in water and its device. It is characterized by that the nitrogen-contained gas is aerated into water, at the same time the high-voltage pulse discharge is made, the discharge electrode is positioned in the water. The pulse width of the described pulse discharge is 200-500 NS, the rise advancing edge of pulse voltage is less than 20 NS, the pulse frequency is greater than 50H2, peak voltage is greater than 10 KV and discharge time is above 3 min so as to obtain nitric acid solution. The device using said method includes the following several portions: gas chamber positioned in the bottom portion of main reaction chamber, several aeration micropores and several upwards-projected needle discharge electrodes which are set in the top portion of gas chamber, grounding electrode placed in said main reaction chamber, the output of high-voltage pulse power supply is respectively connected with discharge electrode and grounding electrode.

Unfortunately it seems that the full text of the patent is not available from esp@cenet.

################################################## ###########

Edit: There are several interesting sounding patents at the European patent office. Here's the abstract of an interesting Russian patent (unfortunately the document itself is in Russian):

Abstract of RU2116960
FIELD: nitrogen compound production. SUBSTANCE: nitrogen-containing gases are brought into contact with catalyst at atmosphere pressure and low temperatures, where catalyst consists of carbonyl complexes of transition metals, in particular, platinum group metals, in the form of solids, solutions or suspensions with neutral, acidic or alkaline medium. Nitrogen- containing gases may include reducing and/or oxidizing agents. Final products are ammonia or nitrogen oxides. EFFECT: enhanced process efficiency

[megalomania]

The general theme of the various furnaces and technologies seems to be air heated to nearly 3000 degrees and rapidly cooled gives the best yields of nitric oxide. I am of a mind to attempt a hybrid magnetically expanded arc combined with a tungsten catalyst system. The early 20th century was only just beginning to utilize catalysts when these technologies were being used, but modern chemistry has advanced catalyst technology to a formidable level.

I do not recall, beyond the O'Hare patent I just mentioned above, any type of nitrogen fixation process that actually incorporates a catalyst into the design. O'Hare uses a sparking apparatus similar to the Cavendish design, but with a catalyst. This simple structure benefits the third world locales it is intended to be deployed in.

A catalyst area immediately following a magnetically spread plasma arc might substantially increase yields. The O'hare design of air circulated catalyst spheres might interfere with such a spread arc, but a catalyst coated screen or honeycomb should be just as effective.

Incorporating something like a water cooled jacket outside the container that holds the catalyst might also help increase yields by providing a steep temperature drop for the formed nitric oxide. I wonder even if a tapered constrictor, like a funnel, could hold the catalyst, the wide end has a metal screen to hold in the catalyst spheres, the arc just below it, and the air is forced into a small area at the narrow funnel end where water cooling would be more effective because more of it is near the outer container. This design might also reduce the quantity of alumina catalyst spheres necessary, filling the volume of a cone rather than cylinder, and it might increase catalyst agitation because air pressure would be greater in the smaller volume.

[ETCS (Ret)]

The Experiments to Fight Hunger page has been found again:

http://www.frontier.net/~ohare/

There you'll find many thought provoking possibilities and innovations in dealing with the various methods of making useful materials.

Many downloadable diagrams and explanations.


Tried uploading a couple of samples,but as they are htm files, no joy. :eek:

[ProdigyChild]

At about year 1900 there was a lamp called 'Nerst lamp' produced by Westinghouse. It was better than carbon filament lamps and disappeared only when tungsten filament lamps become available. It used a rod of ZrO2 heated up by electric current. This rod is conductive thanks to the O2- ions that can travel though it quite well when heated to 1000-2000 Celsius.

So why not use this material as electrodes? It melts at 2715 Celsius. No problem with oxidation, because it's already an oxide :)
It's a bad conductor for heat - no idea if this is good (not that much heat loss) or bad (overheating of the electrode).

What's the drawback? Why does no furnace use that stuff?
The only drawback I see is the fact, that ZrO2 is an insulator at room temperature.

[nightandday]

Extracting information about the yield obtained by:

Bian and Ying, Plasma Science and Technology, Vol.9, No.3 (2007)
"Nitrogen Fixation into HNO3 and HNO2 by Pulsed High Voltage Discharge"

In their paper they write:

"...the applied voltage was 20 kV at a frequency of 150 Hz.
The distance between the electrodes was 20 mm" (p.289)

"...the energy input into the reactor was 52.3 W" (p.289)

"...100 mL of distilled water was pured into the reactor..." (p.289)

"After a discharge of 21 min, nitrate nitrogen concentration was 1.36*10^-3 mol*L^-1 with bubbling air..." (p.290)

"The content of nitrite nitrogen did not exceed 5%" (p.290)



Translation:

100 ml aquous nitrate solution of 1,36*10^-3 mol*L^-1 NO3- contains 8.57*10^-3 g HNO3

52.3 W during 21 min is 1.83*10^-2 kWh

Yield: 8.57*10^-3 gHNO3 / 1.83*10^-2 kWh = 0.47 gHNO3/kWh

Probably thats not good enough.

[ETCS (Ret)]

Alumina Aerogel, and other catalysts, is capable of producing Nitric Oxide by heat alone without any electrical power, by means of thermal cycling and controlled airflow.

As it converts to Nitrogen Dioxide in the air stream it may be used either for creating a Nitric Acid Solution or for Direct Nitration of Carbohydrates.

O'hares web pages have the details of the process and several ideas on enhanced efficiency of electrical production of Nitrogen Oxides as well, using bundles of Tungsten welding electrodes as both plasma electrodes and catalyst among them.

http://www.frontier.net/~ohare/solar_powered_nitrogen_fixer.GIF

http://www.frontier.net/~ohare/vortexplant3.GIF

http://www.frontier.net/~ohare/aluminanitr.htm

http://www.frontier.net/~ohare/threetogthr.GIF

http://www.frontier.net/~ohare/Nitrogen_cellulose_fertilizer.GIF

http://www.frontier.net/~ohare/Fertilizer_from_Air.GIF

http://www.frontier.net/~ohare/biogasnitrogen.htm

[FUTI]

Just a random thought...are the various methods (or at least some of them) proposed and used for NOx generation mutually incompatible or can they work in synergy kind action? Rapid heating followed by discharge followed by UV light (or any other tool and source arranged in any possible way)... I hope I explain this in an understandable way. I like idea of using metallic oxides and also magnetically spread plasma. Those ideas bring little life in this thread.

[ETCS (Ret)]

Prodigy Child's demonstration of High Voltage (~20KV) initiated Charged Capacitor (300V) plasma discharge, in #188 above, is very productive.

This is the method used for "Plasma Ignition" in certain automobiles for greatly improved operation of the Internal Combustion Engine. The Charged Capacitor for this application will work with as little as 110 Volts of charge.

So a rather feeble Very High Voltage source could be effectively employed to "trigger" a charged capacitor high current plasma discharge through air in repetitive pulses. That would significantly simplify the power source to the Nitrogen Fixation device.

As it turns out, there are a lotta ways to skin this ol' Cat!

[ProdigyChild]

@ETCS: when the triggering device uses P = 800A x 1kV it is not exactly 'feeble'. It must not be feeble, otherwise it can't drive the parasitic capacitance of the electrodes.
But of course you're right when comparing the average power of the two supplies. The trigger power is neglectable.

I observed a few days ago, that a very high voltage pulse (2cm..4cm arcover) could NOT trigger a high current discharge of a capacitor at 300V, but between 600V and 1kV the capacitor was again happily discharging, even if I limited the current with a series resistor of 50-100 Ohms (i.e. 20A discharge current at most).

So I've built a powerful line voltage booster that can step up rectified AC to 500V easily. I fed the 500V output voltage into the circuit shown in post #188. OMG! I could draw vertical arcs of 9cm length at estimated 2-3A of (now really constant) current.

I thought I could ignite such long arcs with the high voltage ignition device, too. So I pressed the HV ignition button and tried to adjust the electrodes to the maximum HV arcover length. Obviously I had no third hand free to press the main power button at the same time. But the arc ignited anyway?! The MOSFET got into avalanche conduction and exploded in a huge fireball along with the PWM driver, a small capacitor and ALL resistors in their vicinity...

Yes I'm stupid, because I should not use a varistor with a voltage rating greater than the MOSFET's!
The curcuit is really damaged, even some PCB traces have vanished.
What a bad setback.

However from the short experimenting time I'm quite convinced, that using a moderate high voltage of 400-800V would be very advantageous to yield much longer arcs. 800V is well above any recitfied line voltage. Using a step-up converter to boost line voltage makes the people using 230V line voltage and those using 115V more or less equal. Power factor correction is possible, too.

@ETCS: have you read this? http://carambola.usc.edu/research/coronaignition/coronaignition.html
(I searched the web using your keywords ;-)

[ETCS (Ret)]

Prodigy Child,

The sudden discharge of a capacitor can unleash a spectacular and very destructive explosion - not what we're looking for necessarily, but impressive in its power.

It is very gratifying that you witnessed the event without any bodily harm!

I'd be very much interested in seeing a schematic drawing of your test circuit. I'm having some difficulty visualizing how the MOSFET fits in.

I'm uploading a small graphic file that illustrates an effective Plasma Discharge Ignition System for an internal combusion engine courtesy of Tero who is a member of the Hydroxy Group. To get really good control you need a pair of High Voltage Diodes (5KV or better at 3 Amperes rating) in both sides of the circuit. This circuit would also be a good one to use for Pulsed Nitrogen Oxide generation in a suitable enclosure such as O'hare suggests.

The Study you linked to is very interesting and the conclusion reached is surprising. Solid State Tesla Coils make excellent sources of corona disharge and can be easily pulsed. Maybe it is time to pursue this further...

You're clearly onto something!

[ProdigyChild]

The schematic below shows the key components of my arc power supply.
The controllers are not shown. The frequencies at the gates are typical values I've used so far.

T201 is really oversized. T401 is not.
T301 is a bit feeble, I'll replace it by a IRG4PC30U.

[ProdigyChild]

I've rebuilt my arc power supply and improved its ruggedness. In the following measurements no HV ignition is used. The arcs are created by shorting the electrodes and then stretching the arc by hand.

It's very promising that the measurements have shown that long arcs (more than 2cm) have voltage drops of well above 100V. This implies that a supply of 3A current can dissipate over 300W of heat in air. Not that bad.

The measurements and photos were all made at short circuit of 3A and a maximum voltage of 500V. To be precise: if no load is presented then 500V output. If shorted, then current limited to 3-4A. In between the supply tries to deliver 3A (calibrated to 3A@300V). At above 400V it drops below 2A.

The photo shows an arc drawn vertically the coil-shaped electrode down to the table's surface. The photo was shot with speed-light enabled to show the ambiance of the arc. No, the arc is not as feeble as the photo might pretend. It's blinding bright in reality - I used an appropriate aperture to show the details.
The first DSO screen shot is the V/I versus time of exactly the arc shown on the photo. CH1 is arc current, 5A/unit. CH2 is arc voltage, 100V/unit.
The second DSO screen shot shows a slowly stretched arc's V/I versus time.
It can be calculated, that the power dissipation approaches 500W at the time the arc quenches.

I should note that such long arcs at such low ;) voltage are not stable. They move around a bit out of control. A slight air draft wipes them out. This is why I can't produce horizontal arcs of that length - the plasma moves upwards to quickly! 2cm to 3cm horizontally at most. That's why a HV ignition will be required for a 'production system'.

[ETCS (Ret)]

Very nice work ProdigyChild!

Here's an interesting brief of the NOx generation process with photo:

http://www.kronjaeger.com/hv/hv/exp/no/index.html

His main page has a wealth of info too:

http://www.kronjaeger.com/hv/index.html

[megalomania]

I've had this guys page bookmarked for awhile. I think there is a video that goes with his NOx production. Seems to me he shows how he arranges the aluminum foil in the cups and zaps it showing the formation of orange-brown gas. I think the video was on YouTube, I don't see the link if it is.

[ProdigyChild]

I've seen this page some time ago, but lost it again. However, I've never forgotten the intense brown color in that image. To be honest, I've never got such intense color in any of my own experiments :o

I also remember the photo inside a school chemistry book - also an intense brown color was shown in a glass vessel maybe 15cm in diameter.

Why that? I must do something really, really wrong.
When I re-visited kronjaeger's page, I realized he used aluminium foil as electrodes. Perhaps some catalytic effect as mentioned earlier in this thread? I'm always using copper electrodes for their good heat conductivity. I wonder if these are responsible for my low yields.

Being a bit frustrated about the complexity of building a reactor for a high power arc (water cooling 2 HV electrodes, pressure waves, excessive heat, cracking glass vessels,...) I gave a simple design a go: I used the highest voltage spark (50kV+) I can produce at the highest repetition rate (200Hz), covered with a large (2.8l) cylindrical vessel. The (primary) power is about 30W. This system produces NOx without heating up everything. After about 10minutes the maximum color intensity is reached, running the arc for 20more minutes doesn't change the visual appearance any more. That was still not as brown as on Kronjaeger's page. And yes, copper foil electrodes.

[ETCS (Ret)]

ProdigyChild,

For my NOx experiments I've always used Aluminum wire for the gap. Mainly because I've got a fairly good supply of it and it doesn't tend to corrode. I suspect your raising the possibility of some catalysis going on with the aluminum is probably correct.

Kronjaeger's photo may be slightly enhanced to show the effect. My results have not been that intense either.

A really simple "line powered" capacitive discharge unit can be made using a Lamp Dimmer (TRIAC phase control) unit. A small capacitor ( 2 to 4 Microfarads ) is placed in series with the wiring to the primary of the Ignition Coil to limit the charge/discharge current to a safe level. Then the spark output and intensity can be adjusted, within a certain amount of the range of the control, as if dimming or brightening an incandescent lamp.

Did you mean to say that you'd used Aluminum Foil Electrodes?

[megalomania]

I would think any catalytic effect in a system of this design would be negligible. This reaction is caused by the formation of nitrogen and oxygen radicals at the very high temperatures of the arc plasma. One of the most significant aspects of this system is the ability to cool the NOx gasses before they decompose at high temperatures. It is more likely the shape of the electrode influences the formation of NOx gasses.

If you trap and hold the NOx gases inside a container at elevated temperatures then a catalytic effect could be observed. Heated metals will accelerate the decomposition of NOx, and copper would be far more effective at this. In the catalytic oxidation of ammonia, copper has a very low residence time (length of time the formed NO gas can remain in contact with the metal before it decomposes). Copper would probably make a superior catalytic converter except it gets oxidized under such conditions where platinum does not.

The reason the metal should only have a minimal impact on NOx yield is because so very little gas comes in contact with the electrode compared to the arc. This case works for a flowing system with fresh gas constantly being brought in. In a confined container, stirring caused by thermal currents could bring a great deal of NOx gas in to contact with the electrode.

I am interested to see if the process patented by O'Hare actually works. His method uses tungsten oxide coated alumina spheres as a catalyst to increase the yield of NOx after passing air through an electric arc. I have a method now of preparing tungsten compounds to impregnate the spheres, I just need to find a reasonable source for the spheres. Alumina spheres cost a few dollars a pound, but all the companies I found only sell them in bulk. Sigma sells a pound or so, but for over $100. I don't want to shell out $60 for a 50 lb sack of spheres when I will likely never use 49.5 pounds of it.

[ETCS (Ret)]

In the not too distant past I observed an interesting phenomena in one of my Negative Ion Generator units.

The high voltage generator circuit is simply a line powered capacitive discharge into the primary winding of a Xenon Flashtube trigger transformer via a DIAC. The High Voltage secondary is multiplied by a four stage diode-capacitor array to approximately 10 KV.

The original diodes were very fragile and had burned out so I replaced them with 6 KV, 250 mA units. Unfortunately, when finished I didn't coat the exposed diode wires (#22) with high voltage insulating compound. I installed the repaired unit into a clear plastic jar so the circuit board would be visible and observable. Upon powering up in a darkened room I observed that the output voltage was normal, would draw an arc of about 6 mm, and that there was corona discharge on the exposed diode leads. As the leads were tinned I expected that the corona would have little effect on the integrity of the wires.

After about six months of what appeared to be normal operation into the ion emission array, it suddenly failed. When I opened the plastic jar to examine the circuit board the escaping air smelled strongly of ozone, as expected, but the wires which had been emitting the corona discharge were completely eaten through by the corrosive gases! The ends of the wires which remained were the greenish color of oxidized copper and on the surfaces were small droplets of a deep blue liquid. It would seem that the rather feeble corona discharge had produced enough ozone and NOx over that length of time to form small globs of copper nitrate.

After cleaning the "mess" up and repairing the eroded wires I completely covered all the wiring with a high voltage insulating compound and the unit is back to normal operation again; however, this time without the destructive corona discharge!

Even tinned copper wire is incapable of withstanding the assault of a rather feeble high voltage discharge and the ozone and NOx which results.

[Moxus]

In my birkelandreactor, I use a 1400 watts microvawe oven transformer (MOT). My problem is that my electrodes just burns up.
I tried configuring them in a jacobs ladder, letting the arc travel over a larger surface and hence distributing the heat over a large area.
This works, but it also has a problem. The arc constantly breaking and reforming causes considerable radio noise wich is annoying when you try to watch tv or talk in your cellphone, where the interference from the arcs noise is obvious.
So my thought was to use a stationary arc again, from watercooled electrodes. So my electrodes is simply copper tubes wich runs water through.
I expect the copper to corrode, but I dont know how fast yet so that will be interesting to see.

Anyway, I came up with an idea wich allows me to run electrode 1 and electrode 2 within the same water circuit, but yet having the "waterline" physically broken to awoid parasitic currents in the coolant water. And of coruse, also to awoid 8000 VAC from going into the houses water supply, if ran from a water outlet.
What I did was putting 2 pipes into a soda bottle. one to the bottom, and the second just inside the top of the bottle. Then making sure the bottle is 100% airtight. Now, you can run water-in in the top pipe, and water-out in the bottom tube, and the water-out will be totally electrically insulated from water-in, as long as the waterflow is kept at a low level, to allow the waterbeam to beak into drops before reaching the bottom. To increase flow capacity of the device, it is possilbe to fit some kind of spray nozzle to the water-in pipe, letting drops form much quicker.

I hope my idea can be of help, because i read some people over at sciencemadness talk about watercooled electrodes, but the idea stopped right there because the problem of parasitic curents through the coolant water.

[Herro]

mega-

I'm not sure what the bulk prices look like, but I know McMaster(.com) sells alumina spheres down to 1/8"D for ~$1.50 each I, believe. Fairly steep, but you'd have the precise quantity you need. Just a thought.

[megalomania]

That's not the same kind of alumina. The kind McMaster-Carr is selling are ceramic spheres, not activated alumina with a very high surface area. The cheapest I found is a 50 lb sack of 1/8th inch activated alumina spheres, F-200 grade, with a surface area of 355 m3/g for $65.00. It is the very high surface area that is important, as this is to be used as a catalyst substrate. F-200 isn’t even catalyst grade technically, it is a drying material grade, but the catalyst grade has only slightly higher surface area at a significantly greater price.

[willowmp]

@Moxus

To eliminate the rf radiation comming off the jacob's ladder build a faraday cage around it. This should prevent most if not all the rf from leaving the inside of said cage. Its been a while but if I remember correctly its basically just wire mesh making a "cage" around the rf producing object that is grounded. So a grounded screen of metal window mesh would be good.


As for arc length, I havent read through this whole thread but my solid state tesla coil produces quite a long arc, maybe 3 inches or so? I bought said SSTC from information unlimited if you want to go check out their guides on how to build it or preassembled versions.