Distilling Nitric Acid

[jarrod]

I am in the motion of putting together a .pdf and maybe later on a homepage. Anyways I put this together and was hoping for input, anything I left out or if you know a way of increasing yeld/efficiency, I don’t have much experience in publishing so any criticism is welcome. :p
If any see their work in here and don’t want it to be a part of a .pdf just say and it shall be removed.


Distilling Nitric Acid

DISCLAIMER

This is NOT my work, but the work of others pieced together, not even the quotes are mine. I am mealy an editor aiming for a complete simple guide for distilling nitric acid.

PREPARATION

Potassium Nitrate (KNO3)

· Most agricultural grade nitrates come in the form of "prills". These are little BB sized pellets that need to be treated before they can be used.

· You'll first dissolve the prills in the minimum amount of boiling water possible. This will remove the coating that some fertilizers have, and save you the hassle of grinding them to powder.

· Once the prills are dissolved, filter while hot, and allow to cool while covered. The solution will precipitate out crystals of pure nitrate. The longer it takes to cool down, the larger and purer the crystals.

· Filter the crystals and wash with a small amount of cold acetone or 99% isopropyl alcohol to remove the last traces of contaminants.

· After letting the crystals dry out, you now put them in an oven to remove the water of crystallization. This is the water that is molecular bound to the nitrate.

· To remove it, you place the nitrate is glass or ceramic casserole dish so that it's spread out in a thin layer.

· Turn the oven on to 250°F (120°C) and occasionally stir it till it no longer steams and falls apart into a fine powder.

· Remove from the heat and immediately place it in pre-heated jar or can to keep it dry.

Sulphuric acid (H2SO4)

· Chill the sulphuric acid in the fridge prior to distillation, a low initial temperature will help dissipate the heat during addition, minimizing the amount of HNO3 disintegration to NOx that occurs.

DISTILLATION

Notes:

· I would recommend only doing small batches, especially at first.

· To determine the proper amount of nitrate to use with any given amount of acid, you divide the weight of the acid by 98. Multiply the results by the molecular weight of the nitrate that you are using.

For instance, you have 196 grams of sulphuric acid. You also have potassium nitrate. Potassium nitrate has a molecular weight of 101. So, 196 / 98 = 2, 2 multiplied by 101 = 202. Thus, you'd use 202 grams of potassium nitrate with the 196 grams of sulphuric acid.

Though, in actual practice, you'd want to use a slight excess of acid to ensure a complete reaction

· You MUST use an oil bath for this. The oil bath eliminates hot spots, and reduces the tendency to "bump". Vegetable oil is ok, and it's cheap. Mineral oil is better. Don't try motor oil, it stinks like hell when you heat it.

· It’s a good idea not to fill the distilling flask more than one third full as the goo tends to foam up a lot.

RIG PREPARATION

· Set up your distillation rig

· Don’t let the round bottom flask touch the bottom of the oil bath

· DO NOT use a gas burner for this. This procedure requires the temperature to rise very slowly.

· You need to fully submerse the flask (to neck base) to minimise refluxing.

· If you don't have access to a fume hood, you can do this in front of a window with a fan. The vapours are intensely poisonous, and the condenser will not stop some of the oxides of nitrogen, which are formed.

PROCEDURE
· To start, place the concentrated sulphuric acid in the container that's going to be heated. Next, cautiously and in small portions add with swirling or stirring with a glass rod, the dry powdered nitrate by means of a funnel. If there's any visible fuming, STOP! Get upwind and wait a few minutes for it to stop. Then continue until the entire nitrate is added and well wetted by the acid. There should be no clumps.
No matter how slowly you add the nitrate you will always get white HNO3 (nitric acid) vapour being emitted, although it's not pleasant to breathe it's the red/brown N2O that they’re warning against.

· After standing for about an hour in the closed flask, the mixture is heated cautiously.

· The temperature needs to be brought up slowly to 83°C (not over 86°C), over the period of an hour (1.4°C A min), because there is a substantial lag between the temperature that the oil reaches and the temperature in the flask. You don't want to overheat it

“It took a fair amount of time after the boiling started for the acid to start coming
over, which tells me that you have to drive the reaction pretty hard in order to get the nitric acid form in the first place.”

“The first thing you get is a bunch of dark brown vapour, but it turns clear once the acid starts distilling over.”

· The round bottom flask, which is used for collecting the distillate, has to be cooled well, e.g. by placing it in a beaker that is filled with ice water.

· In the experiment the nitric acid that distils is almost pure (@83 - 85 °C).

· As soon as larger amounts of brown NO2 are formed and the distillate has a brownish colour, the reaction is stopped.

· Are larger amounts of HNO3 to be prepared, one should use a ground distillation apparatus and distil multiple times under vacuum in any case. The boiling point of the acid is about 36 - 38 °C @26 mbar, so a water bath is sufficient for heating.

I am grateful for any input

thanx :)

[xyz]

Maybe some info about H2SO4 sources? Like bought H2SO4, boiled battery acid, drain opener, etc. Maybe also say that it can be concentrated simply by boiling in a pyrex container.

[jarrod]

A Pyrex container???
How does that work, I’ve heard of some pretty weird ways of obtaining H2SO4 but Pyrex containers. Wouldn’t there be a large amount of contaminants, such as ink, dyes in bottle, traces of contents from what was in the bottle, How pure would the H2SO4 be?

[xyz]

Pyrex glass, the stuff that lab beakers are made of. It is glass that will not crack or shatter when heated. You can't use a metal container as it would be attacked by the acid and normal glass tends to crack when heated.

All you would do is take your low conc. H2SO4 and boil it in a pyrex container until all the water was removed.

Edit: I am not saying that the H2SO4 is made from pyrex containers, I am saying that it can be concentrated by boiling it in one.

[jarrod]

Yeah sorry
I misinterpreted what you said

[Marvin]

Its mostly good advice, but writing a text on something you havnt tried at least several times yourself isnt a smart move.

I have to take issue with the oil bath though. In terms of decomposition, the oil bath is pointless, heating the flask above the level of the contents is a bad idea, if your getting much refluxing you probably arnt distilling rapidly enough, and you should speed up and/or lag the exposed glassware with glass wool.

If you have a pyrex distilling flask, then direct heating with an electric mantle, or carefully with a non luminous (only blue should be visible) gas flame always below the level of the contents is fine.

If the glass distilling flask is in any way suspect (apart from having cracks in it, which is not acceptable), then very slow, very even heating with a sand bath or low power electric mantle will be the method most likey to leave it intact at the end of the distillation.

Glass bottles, containers etc not designed for heating break very easily, but for those people desperate enough to try it, a sand bath is the way to go.

The temp at which the nitric distills varies a lot with the salt, the amount of water in the sulphuric, and the acid ratios, but expect it to be a lot higher than the boiling point of nitric acid alone, particulaly neer the end of the reaction. Your driving it out of the mixture, as one of the quotes says.

An oil bath containing a flammable unsaturated oil (If its liquid at RTP, then its doubtless unsaturated) at well in excess of 100C outside a flask containing nitric acid, oxidising salts and sulphuric acid at the same temperature is potentially the last experiment someone ever does.

In my experience oil baths are never worth the trouble, even when they arnt dangerous. Buy a heating mantle, they are worth the money is my advice, as is pyrex lab glassware for distillation.

You need some specific health information for both nitric acid, and NOx gasses, as well as what they do to you and why. Search the web, read the MSDS, make sure it is accurate, under and over caution are often equally unsafe in a how-to text.

[jarrod]

Thanx for the tips but a couple of questions

I’m writing this for my own synthesis because I don’t trust any I just read on the internet ( I had a bad experience with LE’s :mad: ), and after several successful distillations it shall be published.

Could any type of insolation (using common sense) work for the prevention of refluxing.

Money is the problem :( so a heating mantel is out of the question, for now anyway. I assume the sand for the sand bath should be dry and as fine as possible.

THE MOST IMPORTANT question I ask is there a table with the salts/acid ratio. the main one I am after is KNO3/100%H2SO4.

[Anthony]

As Marvin said, glass wool is a good choice of insulation. It's cheap, easy to find, a good insulator and I doubt it would react adversely if you were to get HNO3 on it.

If you're really broke, just go up to the loft of your house and grab a handful (wear gloves...).

For the KNO3/H2SO4 you can work out the stoichiometric ratio using a periodic table. Although it may be better to have an excess of one reactant, I'm sure other members will advise.

[Al Koholic]

Even using a sand bath with glass that is not made for heating will not prevent the cracking of the vessle. The glass simply cannot handle the temperature gradient you will require for this operation. I have tried mulitple times to heat standard glass with a fine sand bath very very slowly and steadily and each time, hairline fractures form which only increase in size as you continue heating. This was only to boil water mind you in experiments to see if it could be done.

Its really interesting actually. You'll be sitting there and all of a sudden, you'll hear a somewhat loud *snap*. Nothing will happen and you'll think...oh, must have been some water vapor in the sand escaping, or the metal on the hotplate is flexing or something. Then you'll hear another snap or two and get curious..."what could that be?!" You'll go to the jar which you have been heating soooo ultimately carefully and the water in it is still there, its not boiling just steaming. You pick up the jar/bottle with potholders and all of a sudden you have a steam plume coming at your face and sand/water splattering around because the bottom of the jar just cracked to the point of separation from the body of the jar but nothing happened till you picked it up. Ive never been able to avoid this with a sand bath and regular glass jars/bottles. Just my 2 cents so if I were you, just use laboratory glassware made for heating. Especially with something like distilling HNO3....

[ALENGOSVIG1]

For cheap insulation wrap fleece around the flask. If your really desperate, wrap some alumininum foil around the flask but make sure its not tightly wraped. It should be like a dome around your flask with airspace in between the flask and foil. The foil doesnt work nearly as well as glass wool or fleece but it works in a pinch.

And i dont think its necessary to remove the coating off the prill unless theres lots of it. Ive never removed the coating off my fertilizers and ive never had a problem. My ferts contain very little coating though.

<small>[ February 17, 2003, 04:27 PM: Message edited by: ALENGOSVIG1 ]</small>

[jarrod]

I tried a “heating test” of just normal glass containers about an hour ago and found beer bottles to be the best :D , but I only tested 5 different kinds of glass containers. From these tests I have to agree that normal glass will not do and a distillation rig is next on the list of things to buy.

I just found a supplier of H2SO4 who wants $24AUD for 5letres at 90%
Im a bit suspicious because the average price is normally $40 (if you shop around here) but is around 98%. Is there anything to look out for when purchasing. I really don’t want to kill myself :p . And also can store brought HS2O4 (floor cleaner) just be boiled for concentration like in a battery

thanx

[xyz]

Where do you live? I can get 98% H2SO4 for $40AUD for 15L from the hydroponics shop near me, and I also know a chem supplier 2 hours from where I live that sells it for $17.50 for 15L.

[jarrod]

I live I northern Queensland (Townsville) and only 2 shops in my town stock it, out of about 8 industrial chemical suppliers. The two hydroponic stores said they don’t sell it or order it. One of the stores gave me lip, quote “ when I answered the phone I said NQ hydroponic supplies not NQ chemical supplies.” The lab supplies store wants $55 for 2.5l

If I used Teflon tubing with a bore of 20mm and a couple of ice packs for a condenser would this do. I ask because a condenser is $352.25 from my supplier, does that sound right?

i think im getting screwed :mad:

thanx

[xyz]

The H2SO4 from the lab supplier is probably so expensive because it is an ultra pure lab grade, you need to find a source that dells the 99% pure industrial grade, not the 99.99% lab grade.

Condensers are so expensive because the Aus government thinks people will use them in alcohol/drug manufacture. If you buy one, the lab supplies people have to clear it with the drug squad first.

I would simply have the teflon tube going into the top of a bucket of ice water and then coming out of a hole in the bottom.

Where did you get your teflon tube? I have looked for some before but then decided that my nitric acid still would have to be glass.

[knowledgehungry]

If they charged 352.75 in the US you would definitely be getting screwed... You can get them for around 40$ here. But i am not sure about the exchange rate between US and AUS.

[xyz]

1$AUD is about half the value of 1$USD, so in Australia you SHOULD pay about $80AUD. Like I mentioned before, "they" think that the stills you use the condensers in will be for alcohol/drug manufacture.

<small>[ February 24, 2003, 03:43 AM: Message edited by: xyz ]</small>

[jarrod]

I found a cheap supplier. :D They want $14- 1000ml RB flask, $8 -500ml RB flask, $40- for quick fit glass joints (both) and $85 for a condenser. They also had a 125ml retort for $4.50. That’s my rig set up for almost $150 AUD the only problem is the glass is borosilicate “BOMEX” brand. I don’t know much about this type of glass so does anyone know if it will do with the strong acid fumes and heating. :confused:

Also would a longer condenser (700mm) be better for this purpose than (300 or 400mm) to allow for a longer cooling period, or have I overlooked something.

Thanx

<small>[ February 26, 2003, 04:02 AM: Message edited by: jarrod ]</small>

[xyz]

All glass will withstand HNO3, and as it is lab glass it should take the heat, I am not 100% sure though.

[NERV]

I have several beakers, and flasks made out of BOMEX. They can esaly take heating, and are as chemical resistant as any other type of glassware.

[Mr Cool]

I was wondering what people thought of using NH₄NO₃ and NaHSO₄ to make nitric acid by distillation? I wouldn't want to melt it dry in case the NH₄NO₃ decomposed, but what about adding around 50mL of water per 80g of NH₄NO₃ / 120g of NaHSO₄ and distilling off fairly strong HNO₃, for further concentration from H₂SO₄?
pKa's of HNO₃ and HSO₄^- are -1.3 and 1.9, respectively. So although HNO₃ is the stronger acid, might the fact that it can escape help drive the equilibrium towards HNO₃? Would it escape at an adequate rate for condensation?
I'd like to try it but I have no NaHSO₄, maybe I will pick some up soon unless anyone thinks this is just a stupid idea.
Then, the NH₄NaSO₄ will, I think, decompose on heating to give off NH₃ and re-form NaHSO₄, which can be re-used.
If it works this method would have several benefits:
No H₂SO₄ is consumed, so it can be saved for other reactions;
NH₄NO₃ is very cheap, so HNO₃ of around 60% concentration could be made for less than £1/L;
NaHSO₄ is re-formed so you don't have to spend money on large amounts of it, only NH₄NO₃ is consumed;
Only readily available, cheap chemicals are required.

What do you think? I know that NaHSO₄ can be used at higher temperatures with k/NaNO₃, but in this case the NaHSO₄ is consumed, leading to further cost. So basically, I need to know if this reaction will occur at lower temperatures - are higher temperatures just used to melt the dry reactants and allow the reaction to proceed, or are they necessary due to the kinetics of the reaction?

[xyz]

I am also interested in this method of HNO3 production. I have about 25-30Kg of NaHSO4 so I am not all that bothered about using it up in the process (if I use KNO3). What sort of concentration could be reached using NH4NO3 and would the concentration be any higher if you used KNO3?

[knowledgehungry]

Does silicone react with Nitric? I ask because i need something to seal my distillation apparatus.

[xyz]

I think it would. Use some teflon plumbers tape to seal it.

[jarrod]

Maybe just cotton bandages from a first aid kit, local chemist …wherever dampened with distilled water wrapped tightly around each joint. This way you can easily remove the seal whenever you needed to take it apart.

im not sure if there would be enough fumes to form a low conc. acid on the bandages. Anyway watch the fingers <img border="0" title="" alt="[Wink]" src="wink.gif" />

<small>[ March 15, 2003, 09:41 PM: Message edited by: jarrod ]</small>

[VX]

You could use a thin layer of Vaseline, or silicone grease without problems, you could also use PTFE tape.

Do not however use wet cotton! This will not form an airtight seal, and the fumes will be strong enough to acidify the water, and then react with the cotton, at the same time as the heat is causing the water to evaporate (making the seal even less airtight) and the cotton to burn.

[ALENGOSVIG1]

You really shouldnt use anyhting but glass or teflon throughout your entire setup. Anything else is liable to dissolve and make a big sticky mess, or worse, catch on fire.

I once tried to use a plastic threaded thermometer adapter for distliing HNO3. Big mistake! I left it for an hour to go shopping and when i came back theres was no adapter, just long black smear down the 3-Way Adapter. :o

Thought it would up for awhile longer than that!

[jarrod]

A bit off topic… but would any one be interested in a full step-by-step document for purifying nitric acid using urea and bubbling air through the acid.

I have almost finished composing this document and thinking about posting, if there is interest.

[Mr Cool]

Please, post away! We're collecting all information on getting, making and/or purifying nitric acid, so that bit of information will fit in nicely. It might be a good idea for you to start a new topic on NO_x elimination if there isn't one already.

[knowledgehungry]

Well the silicone appeared to have melted and not only that as i was checking the seals during distillation my still kinda blew up <img border="0" title="" alt="[Eek!]" src="eek.gif" /> . I got sprayed in the arms with some hot nitric... not plesant. Fortunately i was wearing lab goggles. The glass didnt shatter... just the joints were blown apart. I think im gonna give in and buy some DCM off Ebay instead of attempting any more distillation.

[ALENGOSVIG1]

What kind of a still do you have? Ive never really had an incident when distilling nitric, and ive distilled gallons of the stuff.

Are you using proper glassware or is it ghetto rigged? Is it jointed glassware? Like 24/40, 45/50, etc.

<small>[ March 17, 2003, 09:55 PM: Message edited by: ALENGOSVIG1 ]</small>

[jarrod]

Mr Cool or others , do you know any patient numbers or web sites/documents that relate to the topic of purifying the acid. I can’t finish my document until I obtain a little more information, and I have searched over four hours a day for many days. Google, patient databases and science search engines as well. It is REALLY FRUSTRATING not being able to find anything besides the limited info I already have.
Maybe a book that has been scanned or anything you can think of.

ALENGOSVIG1 - I have finished the final copy of the distilling procedure, and thought that uploading it to the forum FTP was a good idea, but I do not have FTP access :( so I ask if you could do this on my behalf, if you are not to busy. (it is a M/S word doc, size 633kb)


thanx

<small>[ March 18, 2003, 06:48 AM: Message edited by: jarrod ]</small>

[ALENGOSVIG1]

Email it to alengosvig@yahoo.com and i'll be happy to upload it for you.

[jarrod]

Here is the final copy. :)

Distilling Nitric Acid

DISCLAIMER

This is NOT my work, but the work of others pieced together, not even the quotes are mine. I am mealy an editor aiming for a complete simple guide for distilling nitric acid.

Reference: <a href="http://216.239.39.120/translate_c?hl=en&ie=ASCII&oe=ASCII&langpair=de%7Cen&u=http://www.chemikalienlexikon.de/cheminfo/betran/si_daten/0501-sic.htm" target="_blank">Safety references nitric acid </a>

ITINERARY

this got screwed up with the UBB coad

PREPARATION
Potassium Nitrate (KNO3)

· Most agricultural grade nitrates come in the form of "prills". These are little BB sized pellets that need to be treated before they can be used.

· You'll first dissolve the prills in the minimum amount of boiling water possible. This will remove the coating that some fertilizers have, and save you the hassle of grinding them to powder.

· Once the prills are dissolved, filter while hot, and allow cooling while covered. The solution will precipitate out crystals of pure nitrate. The longer it takes to cool down, the larger and purer the crystals.

· Filter the crystals and wash with a small amount of cold acetone or 99% isopropyl alcohol to remove the last traces of contaminants.

· After letting the crystals dry out, you now put them in an oven to remove the water of crystallization. This is the water that is molecular bound to the nitrate.

· To remove it, you place the nitrate is glass or ceramic casserole dish so that it's spread out in a thin layer.

· Turn the oven on to 250°F (120°C) and occasionally stir it till it no longer steams and falls apart into a fine powder.

· Remove from the heat and immediately place it in pre-heated jar or can to keep it dry.

Sulphuric acid (H2SO4)

· Chill the sulphuric acid in the fridge prior to distillation, a low initial temperature will help dissipate the heat during addition, minimizing the amount of HNO3 disintegration to NOx that occurs.

DISTILLATION

Notes:

· I would recommend only doing small batches, especially at first.

· To determine the proper amount of nitrate to use with any given amount of acid, you divide the weight of the acid by 98. Multiply the results by the molecular weight of the nitrate that you are using.

For instance, you have 196 grams of sulphuric acid. You also have potassium nitrate. Potassium nitrate has a molecular weight of 101. So, 196 / 98 = 2, 2 multiplied by 101 = 202. Thus, you'd use 202 grams of potassium nitrate with the 196 grams of sulphuric acid.

Though, in actual practice, you'd want to use a slight excess of acid to ensure a complete reaction.

· You MUST use a sand bath for this. The sand bath eliminates hot spots, and reduces the tendency to "bump". The finest sand possible (smallest grain) and it should be dry.

· It’s a good idea not to fill the distilling flask more than one third full as the goo tends to foam up a lot.

RIG PREPARATION

· Set up your distillation rig


· Use a thin layer of Vaseline to make an air tight seal around the joints.

· Don’t let the round bottom flask touch the bottom of the sand bath as a “hot spot” may occur.

· DO NOT use a gas burner for this. This procedure requires the temperature to rise very slowly.

· You need to insulate the neck and non-heated areas of the flask with glass wool to minimise refluxing.

· If you don't have access to a fume hood, you can do this in front of a window with a fan. The vapours are intensely poisonous, and the condenser will not stop some of the oxides of nitrogen, which are formed.

PROCEDURE
· To start, place the concentrated sulphuric acid in the container that's going to be heated. Next, cautiously and in small portions add with swirling or stirring with a glass rod, the dry powdered nitrate by means of a funnel. If there's any visible fuming, STOP! Get upwind and wait a few minutes for it to stop. Then continue until the entire nitrate is added and well wetted by the acid. There should be no clumps.
No matter how slowly you add the nitrate you will always get white HNO3 (nitric acid) vapour being emitted, although it's not pleasant to breathe it's the red/brown N2O that they’re warning against.

· After standing for about an hour in the closed flask with occasional swirling or stirring with a glass rod, the mixture is heated cautiously.

· The temperature needs to be brought up slowly to 83°C (not over 86°C), over the period of an hour (1.4°C A min), because there is a substantial lag between the temperature that the sand reaches and the temperature in the flask. You don't want to overheat it

“It took a fair amount of time after the boiling started for the acid to start coming
over, which tells me that you have to drive the reaction pretty hard in order to get the nitric acid form in the first place.”

“The first thing you get is a bunch of dark brown vapour, but it turns clear once the acid starts distilling over.”

· The round bottom flask, which is used for collecting the distillate, has to be cooled well, e.g. by placing it in a beaker that is filled with ice water.

· In the experiment the nitric acid that distils is almost pure (@83 - 85 °C).

· As soon as larger amounts of brown NO2 are formed and the distillate has a brownish colour, the reaction is stopped.

· Are larger amounts of HNO3 to be prepared, one should use a ground distillation apparatus and distil multiple times under vacuum in any case. The boiling point of the acid is about 36 - 38 °C @26 mbar, so a water bath is sufficient for heating.

<a href="http://216.239.39.120/translate_c?hl=en&ie=ASCII&oe=ASCII&langpair=de%7Cen&u=http://www.chemikalienlexikon.de/sichhinw/entsorg/entsorg.htm" target="_blank">References to the disposal</a>

[knowledgehungry]

It is standard lab glass however it is not a vacuum distillation. It is a flask an adapter then another flask.</font><blockquote><font size="1" face="Verdana, Arial, Helvetica">code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">
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^^flame </pre><hr /></blockquote><font size="2" face="Verdana, Arial, Helvetica">Thanks Anthony.

<small>[ March 19, 2003, 09:52 PM: Message edited by: knowledgehungry ]</small>

[Anthony]

A few spelling/grammar errors.

"The finest sand possible (smallest grain)"

Is that really important? I'd have thought as long as it wasn't gravel, it wouldn't have made much difference.

"the goo tends to foam up a lot"

Nice tech term <img border="0" title="" alt="[Wink]" src="wink.gif" />

"Use a thin layer of Vaseline to make an air tight seal around the joints"

I'm not sure on this one, but it doesn't sound right - HNO3 vapour in contact with flammable hydrocarbons. IMO I'd use teflon (PTFE) plumbing tape if leak sealing is required.

"If there's any visible fuming, STOP! Get upwind and wait a few minutes for it to stop"

I think you need to stipulate red/brown gas, rather than just "fuming", to avoid confusion. The appendum concerning NOx added on the end seems disjointed, and why write something and then correct it, just say it right first time :)

"After standing for about an hour in the closed flask with occasional swirling or stirring with a glass rod, the mixture is heated cautiously"

It would be useful to state *why* the mixture needs to stand for an hour. To cool down? Worth saying as it will be variable. To allow it to react? Does it really take that long? I've never waited that long when doing nitrations with xNO3/H2SO4.

BTW knowledgehungry, use the CODE tags to stop UBB screwing with your ASCii art.

[Mr Cool]

Knowledgehungry, where's the port to allow the expanding gases to escape? Once the mixture and everything else is up to the right temperature and you're distilling you shouldn't have a problem, but while you're heating it up the air will expand and pop your joints out.
Anthony, I use vaseline to lube the joints. You don't need it to get a seal, but it stops the joints from jamming together. I've never had a problem, and I doubt that I ever will. You only need a tiny amount, even if it did burn not much would happen. And consider that it never gets above 90*C ish.

[Anthony]

K, just wanted to be sure :)

[knowledgehungry]

Well that is kind of the problem. I didnt use an outlet for the gas to escape. I knew i should have but i thought that i would have to keep the hole open the whole time, but now that i have been informed that there needs to ba a vent only while the temparature is still climbing i think i might try it again with a vent of some sort. 90*C? Do you use a vac distillation?

[Mr Cool]

No, I don't use a vaccuum, but I do use 70% HNO₃ + 98% H₂SO₄, instead of a metal nitrate and 98% H₂SO₄. I haven't ever measured the temperature that it distils at, since the thermometer that I have that can be attached to quickfit is not HNO₃ compatible. But I would guess it to be no more than 90*C, considering HNO₃'s boiling point.

[Celtick]

How many ml of 98%H2SO4 do you use with an ?ml 70%HNO3?

[Mr Cool]

I use a 1:1 ratio by volume of 70% HNO₃ to 98% H₂SO₄.
To give you an indication of the usefulness (or otherwise) of the acid produced, 2mL of acid with 1g of HDN will give ~0.6g of RDX using the common method (add HDN to acid at 20-30*C, raise temperature to 50-55*C once it has all dissolved, hold for 5 minutes, cool to 20*C, hold for 5-10 minutes (I chose to use 7 minutes, for no particular reason), dump into water, wash, recrystalise from acetone, dry). That is with a single distillation at atmospheric pressure, with no attempt made to remove NO_x, based on a batch using 15g of HDN and 30mL of HNO₃, yielding 9g of purified RDX.
The acid will also give yields of purified PETN of between 85% and 90%, based on batches using 10g of PE and around 35mL of acid (therefore &gt;19g of PETN).

[simply RED]

Mr Cool, what equipment do you use for this distilation?

[Mr Cool]

Quickfit, a 1L rb flask to heat the mixture in and a liebig condenser about 10" long roughly, cooled by syphoning water from one big bottle on my bench to another that is below. Then I have a delivery tube to drip the HNO₃ into a collecting flask. I normally distil at a rate of about two drops a second, ie, heating strongly but not really blasting it.

[xyz]

Mr. Cool, What did you use for heating, distributing the heat, and stirring?

<small>[ March 27, 2003, 03:05 AM: Message edited by: xyz ]</small>

[bubbling_beaker]

hi,
Mr Cool; Is your entire distilation setup sealed, or does the HNO3 just drop from the condenser into your collection vessle?

[Mr Cool]

Heated with a bunsen flame from below, no extra effort is used to distribute the heat, no thermal insulation is used on the flask containing the mixture, and the only stirring is that provided by the bubbles in the boiling liquid. I use a few pieces of silica grit as anti-bumping granules.
So, just normal heating really :) .

My entire setup is not sealed; the end of the delivery tube that is attached to the condenser is open, allowing the acid to drip into an open beaker (which, btw, I never bother to cool down).

To clarify, <a href="http://www.boomspeed.com/mrcool/DistillationSetup.jpg" target="_blank">here</a> is a picture of the glasswear that I use for simple distillation. Also shown, on the left, is a simple fractionating column.

<small>[ April 03, 2003, 01:20 PM: Message edited by: Mr Cool ]</small>

[jarrod]

I have recently completed my purification method, sadly though there is very little information on this topic. :( If there is info out there then I sure as hell cant find it. :mad: The information I have found left the reader open to interpretation, there for I am positive the synthesis I have composed is going to have errors all through it.(this is why it is not a new poast) This is where I ask that you let me know where I can fix it up, since multiple opinions is always the best method of obtaining the correct information. (or close enough to)

Nitric acid purification

PURIFICATION

The nitric acid obtained at the end of my distillation is red to yellow-red. What this means is there is NOx present in our acid. NOx is not wanted so we need to extract it using an air pump, Teflon tubing and urea. The air used for bubbling needs to be dry, the air around us has too much moisture in it. To dry air is to desiccant air, for those that didn’t know that <img border="0" title="" alt="[Wink]" src="wink.gif" /> .

PREPARATION

· Obtain a tube that can be used for drying gases eg, U-tube (an improvised tube will do) and fill tube with the drying media. (Silica gel, Activated Clay (Montmorillonite) or others.)

· Get your pump and find the inlet hole/valve, (this is where it sucks the air in) put your thumb over the hole to completely cut off intake. Turn the pump on and see if air is still being pumped through. If so then take you pump apart and find where the air is being sucked in,(some pumps have more than one inlet.) To detect the air intake if it is not easily seen, blow smoke on the pump area and you should be able to see where the smoke is being sucked in. After these holes are found, block them, leaving one inlet open (use glue, silicon or whatever it calls for.)

· Attach the drying tube to this hole/valve. Do not attach the glass directly! Use tubing, because this is how you will brake your glassware. (But we all knew that already… didn’t we.) Make sure there is NO leaks, reinforce your joints with “plumbers tape,” this is the white tape that is often around plumbing joints.

· Hook the Teflon tubing up to the tubing from the pump (using an improvised joiner eg: duck tape.) Again make sure there is NO leaks.

PRODUCER


· First fill a round bottom flask with your impure nitric acid (not to full to allow for error, 1/2 is sufficient) we do this because this because we don’t want any acid to spill on our skin or cloths, OUCH!

· After inserting the Teflon tube into the acid start bubbling dry air through it, (A constant stream of dry air, not so much as to cause the acid to foam up but enough to have lots of nice little streams of bubbles, youse your judgment.) You can slow the flow of air by slightly clamping the tube using a peg or something else.

· Ratio for urea addition is 1g urea to 100g acid

· For 100g acid add the urea over a time of 1 hour (0.1g every 10min) and continue bubbling for another 2 hours. (If you have twice the amount of acid double the urea and the bubbling time, if three times then triple it, ect.)
(this was an educated guess)

· Swirl the flask (for a good minute) every time you add urea and then every now and again for the remainder of the bubbling.

· When bubbling is finished remove the tubing from the acid and while still inside the flask let any acid drip off.

· Our acid is now ready for use in other synthesises.

BUBBLER

· There are many ways to make a bubbler this is just one idea, just remember it all needs to be Teflon or resistant to the acid. Make a bubbler by blocking the end of the Teflon tubing and poking holes in it. Start by cutting two 10mm lengths of tube off the end.

Þ Cut down one side so it folds out and you have a rectangle of Teflon. Flatten this piece. (In a clamp, under some books ect…) after it is flat and will not curl, cut a circle out that has a diameter the same as the bore of your tube. (keep the scraps) DO THIS TWICE

<a href="http://www.angelfire.com/pro/jarrod/images.html" target="_blank">pic #1</a>

Þ Carefully insert the circles as to perfectly fit and block the tube (DO NOT glue, place it and leave it there)

<a href="http://www.angelfire.com/pro/jarrod/images.html" target="_blank">pic# 2</a>

Þ Cut strip of Teflon from the scraps you saved. Poke a hole through the very end of the tube, now thread the strip through the holes. Thus blocking the most of the airflow, there will be air still coming out. (it should not be to much)

<a href="http://www.angelfire.com/pro/jarrod/images.html" target="_blank">pic #3</a>

Þ Now poke holes up the tube for the next 40mm (after the circles finish) and there is your bubbler.

· Test your bubbler in water and “tinker” until you have lots of nice little streams of bubbles coming from each of the holes you poked.

· Hook it all up so you’re ready to pump “Dry Air.”

So what do you guys/gals think?

[stanfield]

interresting...
why the addition of urea must be so long ?

Today, I've tested this method :
H2SO4 + Ca(NO3)2*4H2O = 2HNO3 + CaSO4
my sulfuric acid : 96%
so, thoritically, 10ml of acid with 44g of nitrate...
I poured 10ml of acid in a small beaker then added, about 20g of nitrate an the stuff became like a paste ! impossible to stir !
How the hell could I add 44g of nitrate in so few acid ? is the equation right ? are my ratio right ? (I did these calculation quickly, so, there may be an error...

bye.

[Marvin]

When you ppt CaSO4 from conc solutions thats what always happens. Even from dilute solutions you get something that is god awful to filter. Letting it settle, decanting and writing off the loss of product is normally easier. but its useless in this case. You may find an excess of sulphuric acid helps prior to distilling, but so long as the nitrate is anhydrous, it should distill ok to good nitric.

[stanfield]

Thanx for the answer...
I wanted to try this method because many people say this is the best. (?)
ok, so if I well understood, by distilling (and so, heating) the mixture, it should be ok, that's right ?
I prefer asking before doing because I don't want to waste my sulfuric acid.

By the way :
One day I mixed 1:2 low nitric acid/sulfuric acid, and distilled this. At the end of the reaction I obtained a very good yield of concentrated nitric acid and the distillation time was fine too.
So, I get back diluted sulfuric acid that I boiled down today.
At the begining of the heating, (when the acid is always cool...), the color of the acid was transparent. Next, it became red/yellow because nitric acid remained. Next the mixture boiled and red fumes were released. At the end of the heating, the sulfuric acid stopped boiling, blank fumes were releasing but yellow color remained, why ?? I think I get back near 100% sulfuric acid but what is this yellow color ?

thanx !

<small>[ April 06, 2003, 12:58 PM: Message edited by: stanfield ]</small>

[IPN]

Sulphuric acid is colorless when it is very pure, but usually it is yellow (this happens when the concentration is very high).
Mine is always colorless after concentrating (from battery acid) but after a while it turns yellow :confused: .
So you don't have to be worried about the color.

From ChemFinder:

</font><blockquote><font size="1" face="Verdana, Arial, Helvetica">quote:</font><hr /><font size="2" face="Verdana, Arial, Helvetica"> Colorless (pure) to dark brown, oily, dense liquid with sharp, acrid odor. HYGROSCOPIC. </font><hr /></blockquote><font size="2" face="Verdana, Arial, Helvetica">

[stanfield]

cool, I get back very high concentrated sulfuric acid ! fine.
What are the white fumes released ? sulfuric acid only boils at very high temperature, so these vapours aren't sulfuric acid...?

<small>[ April 06, 2003, 05:19 PM: Message edited by: stanfield ]</small>

[IPN]

The fumes are probably a mix of SO2/SO3 (I’m not sure though.)

Nothing really concerning unless you are working inside the house..

[jarrod]

I made the addition of urea so long because I did not find any information at all with time frames, :( and after a bit of thought I decided that bubbling should go for three hours and urea addition for one hour to ensure elimination of NOx. Also it can always be corrected if new information comes to my attention.

Just to clarify what I said in my previous post. “ (this is why it is not a new post) ”
I intend to post this as a new topic so anyone searching can find it rather faster than having to read through many posts, just to make things simpler. :) Also I would prefer to have a relatively correct procedure as to save confusion due to jumping around a lot with ideas.
So any comments before I make the switch.

thanx

[Mr Cool]

White fumes from hot sulphuric acid are probably just sulphuric acid droplets. Vapour will come off even when it is not boiling, as the vapour/air mixture cools the air can hold less, so the vapour forms droplets of acid which appear as a fine mist.
I normally don't bother to add urea to my nitric acid, after distilation it is only very slightly yellow and clears up after a small amount of hexamine is added. It seems to do the job of urea. Once, though, I had a batch of quite dark yellow nitric due to careless distilation, and I added around 1.5% of urea to it. I can't remember exactly, but it was a small amount of acid, 50mL maybe. I added the urea all at once, very foolishly, and got a vigorous reaction which made the acid much darker (the urea reacted with the acid, forming urea nitrate and nitrourea, releasing heat, which decomposed the acid). So add it slowly, with stirring.

[Anthony]

I don't think it is a good idea to specify a specific time for the additions, unless who have a good reference for it, or have determined it yourself emperically.

An specific instruction that is found to be inaccurate could bring the entire process(es) into disrepute/distrust.

[stanfield]

I always added my urea in one time... never got a problem when making PETN...

[HypersonicGamer]

So if someone originally had a somewhat lower concentration of HNO3 (70%) and mixed it in a 1:2 ratio with H2S04 (98%) - and distill, the yield would be a high concentration of Nitric Acid?

[mongo blongo]

Yes. The H2SO4 will absorb water and hold it back during the distillation.

[jarrod]

Anthony - I also thought along those lines, but what guidelines do you give this procedure that don’t have a quantitative ring, and that is still able to make sense for those just beginning. :confused:

[Anthony]

Try it and see?

Some other members have also given brief accounts of their experiences.

[jfk]

Just a few things which might be of use/interest.

100% sulphuric acid isn't an acid, for it to be acidic there must be some water molecules for it to dis-associate into H[+] and SO4[2-] in.

And Borosillicate glass is the stronger grade of glass that lab ware is made out of. According to my supplier you can heat borosillicate glassware quite a bit higher than the other grade, which i hazard to say is just tempered glass.

[knowledgehungry]

I f you want to get technical JFK(i thought you were dead) 100% H2SO4(unless in a perfect vacuum) will have at least 1 H2O molecule as H2SO4 is hygroscopic, there is no such thing as 100% pure anything.

[Einsteinium]

100% sulphuric acid isn't an acid Yeah, that's probably why they called it ACID :rolleyes:... Anhydrous (or theoretical 100% pure) sulfuric acid is an acid, it have no pH since it's not in aqueous solution but it still can give it's acidic protons to say, NaHCO3 or NH3 in anhydrous conditions (very high-vacuum or under inert atmosphere)... It may also reacts, as an acid, with water (a base) to generate a less acidic hydronium cation and a bisulfate anion... acid/base theory 'me boy!

[jfk]

ok, woah didn't want to get that technical, but one guy above did ask about using 100% sulphuric acid, since it is hungry for those water molecules it will have at least one from the atmosphere unless its in a vaccum. so if its not in a vaccum, chances are its absorbed at elast one H2O from the armosphere making it, what 99.9999999999999999999998 % pure or something, right?

yeah jfk is dead, but my full alias, i thought Americans to be sensitive of, so i have recently changed it to just jfk.

[Einsteinium]

For all practical purposes there will be water in the acid, but keep in mind there are ways to remove mostly all water from the acid withouth the need for an extremly pure acid. You just have to add something that reacts with water to the acid (there are thousands; lithium, acetic anhydride, LiAlH4 etc...) while performing this step under an inert atmosphere. Distillation, under inert atmosphere, will give the anhydrous acid if everything else was anhydrous. It takes skills to achieve this properly and this is quite useless since the 98% solution contains 98% pure acid and 2% impurities + hydroniums (water), bisulfates. Water decreases the acid's power, it dosen't activates it's acidity. BTW, theoretical pure sulfuric acid is roughly 10^12 times more acidic than a 1M aqueous solution of the same acid, respect the stuff :D

[Marvin]

Id expect both lithium and lithium aluminium hydride to react with sulphuric acid itself rather than just with the water, the former liberating hydrogen to form a salt, and the latter reducing it to sulphur, amongst other things. I assume you meant to concentrate sulphuric, since these options only get worse for the direct production of conc nitric. If acetic anhydride was used, this would contaminate the sulphuric with destruction products.

I doubt more concentrated acid is needed than can be made just by driving off the water by heating, but for anyone that wants less water, the method suggested to me to dehydrate sulphurc acid, was to heat sodium hydrogen sulphate to form the pyrosulphate, and add to the warm acid, cooling deposits insoluable sodium sulphate (or possibly hydrogen sulphate). Some sodium ions doubless remain in solution, but could be removed by distillation if absolutly required. The temp required to distill conc sulphuric acid is a little high for most glassware, my books recommend quartz.

What jfk meant, I think, was that pure sulphuric acid is a bad conductor of electricity becuase its sparsely dissociated. Adding some water to it sharply increases dissociation, and its conductivity.

[10fingers]

In regards to concentrating sulfuric acid I have always boiled down battery acid. I have found though that you need to continue heating for about 20 minutes after white fumes start coming off to get a high concentration acid. I have gotten it to a density of 1.83 doing this which is adequate for most purposes. I always use a coffee pot. If you do it on an electric hot plate though, don't set the pot directly on the heating element, use some type of spacer to give it about 1/2 in. clearance. Putting the pot on the heating element will cause it to crack.
For distilling nitric, don't mess around with bottles and shit like that, it's a wast of time. You can buy a complete ground glass joint distillation setup from www.unitedglasstech.com for around $135.00. It is one of the best investments I have ever made.

[Arthis]

If you want to quibble about the concentration of sulfuric acid, I've heard that an excess of up to 30% of SO₃ (the gas) can be dissolved in sulfuric acid, thus giving a yellowish substance that is known as "oleum" if I remember well.

So you can get more than 100% sulfuric acid. :)

[Arthis]

This morning i tried to distill some nitric acid but I fucked with my sand bath, as I don't have any power regulator (if anyone has some plans to make one cheap), and I got lots of red fumes, and quasi no acid (very orange of course).
The problem is that I turned off the heater, to allow the temp to rise down, then when I started it again, nothing happened: it seems that there was no more nitric acid to be distilled.
The fact is I used about 50g AN, with 100mL 92% sulfuric acid.

Do you think AN is good to be used, or would you advise KNO3/NaNO3 ?
My AN is fertilizer, it's written on the bag N from nitrates: 16%, from ammonium: 16%. I think it's normal pure AN but do you confirm that ?

Thanks, I'm gonna try again and see what happens.

Note: after having stopped the system, as it wasn't distilling anything more, I put a thermomether in the flask, and it instantly went up to 110°C, its maximum. Why would the temperature have so rised while no fumes, nothing was being distilled ?

[Marvin]

I dont like the idea of using AN for producing nitric acid, mainly becuase of side reactions like dehydration that cant happen with alkali nitrates,. Though some people here do it.

If you are measuring the temperature of the solution, expect it to go a lot higher than 110C. End point in a neutral alkalie sulphate product reaction is something like 260C, youd never go that high with AN though, aim for mostly bisulphate if you redo the math, or use existing figures.

The reason hot sulphuric acid 'fumes' is probably more to do with the reason conc HCl fumes than strictly condensing acid. The conc acid vapour is very hygroscopic, so it absorbs water vapour from the air, the dilute acid has a lower vapour pressure than the water did, so you get the fine mist. Just the ramblings of a bored mind.

[Tuatara]

Arthis, if you want a really easy power regulator for your hotplate/sandbath go to your nearest electrical wholesaler (the sort electricians get supplies from) and buy either an oven thermostat, or an 'energy regulator' of the type used for controlling the hob elements. I bought a thermostat (50C - 300C) for NZ$60 last week (about US$30), an 'energy regulator' would be the same or less. The difference between the two is that the thermostat regulates temperature , the energy regulator controls the average power . The latter would likely be of more use for distillation. Both should handle at least 2kW easily.

[Vigo]

Hello, this is my first reply and I hope I am contributing to the forum and the beast does not catch up on me!

To complete the guide on distillation:
Despite it being flammable liquid, paraffin can be used to create a heat bath because it has such a high boiling point, ussually over 400°C. It has a heat capacity of 2.13 kJ/kg.K which is about half that of water. Therefore it will heat the distillant evenly. Paraffin is a mixture of hydrocarbons, hence its boil and flash point are determined by its composition (the larger the percentage of large molecules the higher the boiling point). I know for a fact that it is used in determining the melting point of aspirin (138°C) in school labs in presence of an open flame (the paraffin is in a heat diffusion test tube).

to Jarrod: I strongly derecommend using cotton to seal a home made distiller if nitric and sulphuric acid are in the distilling bulb. If vapours come into contact with it, it will turn into a nasty black mush. There is a very slight chance it turns into gun cotton and you do not want that. I know gun cotton has to be very dry and have a neutral ph but after all it is near a heat source and water which could increase the ph and dry it (very unlikely though).

[beez21]

Hello,
I was just wondering if it would be possible to concentrate Nitric acid by freezing it in a normal home freezer, because the water would freeze allowing the nitric acid to, just be poured out. Would this work or am I missing something? Please tell me if this is a stupid question, but I did a quick search that didn't return anything useful!

[Nitric-producer]

I doubt it otherwise why would we all bother with Distillation etc. ;) Im pretty sure it would just freeze into a big large chunk.

[beez21]

Yes I did think that but I was just making sure. With the freezing points being so different -42 degrees and 0 degrees, I thought it might have worked. Looks like I'm going to have to splash out on a Distillation set. bye bye money :(

[nbk2000]

UTFSE will show a thread where I posted about my experience with freezing out nitric acid from DMC (methylene chloride).

You don't need a distillation setup if you extract/freeze, though you'll still want a setup for purifying the DCM for reuse.

[beez21]

Oh, really sorry I'll search more Thoroughly next time! it wont happen again :o

[ultma]

I f you want to get technical JFK(i thought you were dead) 100% H2SO4(unless in a perfect vacuum) will have at least 1 H2O molecule as H2SO4 is hygroscopic, there is no such thing as 100% pure anything.


I take it you have not heard of 110% sulfuric acid
you add 10% water you still have 100%

I think its made by bubling SO2 through 100% H2SO4

[nbk2000]

It's called 'oleum', and is sulphuric acid with an excess of Sulfur Trioxide dissolved in it. Any additional water added to oleum results in additional Sulphuric Acid, until all excess SO3 is consumed, making it a very effective dehydrating agent.

[xenon24]

A little OT, but since you brought it up...

NBK (or anyone else), do you know where to buy oleum, or how to make it? Based on the research I've conducted it's very hard to make sulfur trioxide (whereas sulfur dioxide is made by simply burning sulfur) I've done searches on oleum before and never found much.
I'd like to make 2,4,6 - trinitrotoluene, but I don't have the resources to make/haven't found a place to buy oleum.

It is also a solid if you add enough Sulfur Trioxide, and this is how it is transported...makes for a nice desiccator.

[nbk2000]

Roasting iron pyrites in a furnace will form crude oleum, or crystallline SO3, depending on reaction conditions.

Buying it? Not too likely.

Besides which, you don't need oleum for making TNT.

[akinrog]

Roasting iron pyrites in a furnace will form crude oleum, or crystallline SO3, depending on reaction conditions.

Sorry to interject Sir, but AFAIR, burning pyrite gives SO2 which was further oxidized into SO3 either by means of a catalyst (Vanadium oxide?) or contact process. Regards.

[nbk2000]

You're not burning them in air, you are destructively distilling them (roasting).

I read this in an old book, maybe Dicks or Ullman, so perhaps it was incomplete or just plain wrong. Go to primary sources.

I also found this:

Sulfur trioxide can be prepared by the two-stage pyrolysis of sodium bisulfate:

2NaHSO4 > Na2S2O7 + H2O
Na2S2O7 > Na2SO4 + SO3

This method will work for other metal bisulfates, the controlling factor being the stability of the intermediate pyrosulfate salt.

Source (http://en.allexperts.com/e/s/su/sulfur_trioxide.htm)

So roast sodium bisulfate until all steam evolution is done, then crank up the heat to cook off the trioxide.

I wonder if you could do this with super-cheap ag. grade ammonium bisulfate?

[megalomania]

Oi! Isn't this a thread about nitric acid? I was spending (actually wasting) no small amount of time yesterday researching the preparation of SO3. I decided to stick to nitric acid this summer, so no goodies for sulfuric will be forthcoming for now.

Oleum consists of sulfur trioxide dissolved in sulfuric acid, not sulfur dioxide, ultma. It is true that a common industrial route to sulfuric acid is the roasting of iron pyrites in open air to form sulfur dioxide. I can't vouch for the anaerobic method, but it sounds reasonable. It probably requires more heat energy (read that as $$$ wasted to industrial types), which is why it is not used commercially.

[Squizzy]

Hi my first post bear with me.

I went a different tack in equipment to make nitric acid.
Instead of using a glass vessel i bought a camp oven around 2 litres and drilled a hole to make a tight fit on a distillation head. I then added the potassium nitrate prills and went to the luteshop and bought some lute (clay).

I smeared this liberally around the rim and the distillation head hole after assembling it all. Attached a condensor and a 3 litre flask to hold the condensed nitric acid. This receiver had a extra small neck for a thermometer to which i attached a rubber tube which i laid out to lead fumes off. Then i added sulfuric acid through the distillation head and sealed it afterwards with a stopper to fit. Then i actually used a gas flame to heat the mixture. Id seen this idea of using iron vessels in a old chemistry book from the 1850s in a google book search.
Some of the old chem books on googlebook have some gems for home experimenters

After use and rinsing its only got a medium coating of surface rust on it and would seem to be able to be used many times. Getting the clay lute to seal can be problematic. but if it leaks slap some more on. Even go around the outside with more They used coal fires to heat similar iron vessels so a gas flame set for a nice mild distillation should be safe. The only problem was you cant see the end point of the distillation. I didnt boil it dry to the evolution of red fumes , instead I judged the output but I found on dismantling there was still much liquid in the iron vessel. I was erring on the side of caution though.

The acid performed well in making Aqua regia I didnt triturate for strength of the acid

I also heated the iron camp oven to extreme heat. The aim to burn of any oils and paraffin used as a rust preventitive on the assumption it might nitrate into a explosive in a nitrating environment like that.

In hindsight glass would have served as well but for making red fuming acid RFNA iron would possibly save your glass

[James]

Just a quick crazy thought, why not use an old fashioned pressure cooker with the stem removed. Then you could attach a tube (and ultimately the condensor etc.) where the stem was. I have a pressure cooker that I could use for something like that.

[Frunk]

Just a quick crazy thought, why not use an old fashioned pressure cooker with the stem removed. Then you could attach a tube (and ultimately the condensor etc.) where the stem was. I have a pressure cooker that I could use for something like that.

What makes you think the stainless steel that the pressure cooker is made out would resist boiling nitric acid? That's an old trick for distilling water or alcohol, but acids are another beast.

[megalomania]

It would work for awhile, but eventually corrosion would become an issue. Actually highly concentrated nitric acid passivates many metals, whereas dilute nitric acid will attack them. Maybe the steel container will last for a time. Certain steel alloys exist that will resist acidic environments, but I doubt the steel in a pressure cooker would be made of such an alloy.

If you were distilling large amounts of nitric acid on a regular basis I would suggest going with a glass setup, but for the casual distiller in a pinch there would be nothing wrong with using a pressure cooker. Distilling nitric acid once in a steel pot should not go wrong. Even a corroded pot should not affect the overall purity of nitric acid, but structurally it would be dangerous with each use. Spilling hot nitric acid all over your work area does not a fun day make.

[Bluebanshee]

I came across a good way to produce concentrated sulphuric acid while reading through an old Encyclopaedia Britannica (1938 edition or thereabouts) it details the method by which it used to be made in industry in the good old days and before the contact process was invented. it uses hydrated Iron II Sulphate, also known in those days as "green vitriol" (FeSO4.7H2O). to produce sulphuric acid, which also used to be known as "oil of vitriol".

The iron II sulphate is a green solid (the green colour is due to the H2O ligands), and it can be purchased from garden centres (in the UK at least) as a soil treatment.

i have checked out the thermochemical data on iron II sulphate in my "Nuffield advanced science book of data" it gives the decomposition temperatures listed below.

The method is as follows: Put the iron sulphate in some kind of vessel and heat gently. At a temperature of 363 K, the material will lose 6 of the water of crystallisation molecules. FeSO4.7H2O -----> FeSO4.H20. this new material is white, hence the process can be monitored visually by colour change.

Put the white solid in a distillation apparatus and heat strongly. At a temperature of 573 K the material decomposes into sulphur trioxide and iron oxide and the remaining water of crystallisation molecule is given off.
FeSO4.H2O ------> FeO + SO3 + H2O. This reaction can again be monitored visually as the FeO has a very characteristic red brown rust colour (funny that)

note that 1 mole of SO3 plus 1 mole of H2O will react to give 1 mole of H2SO4 (sulphuric acid) and this will be distilled over and can be condensed to give very concentrated sulphuric acid.

I have tried this and it does work, main points to note are, ensure that you only heat gently at first otherwise you fully decompose the material too early and waste it. also make sure that all traces of green have dissapeared before collecting the distillate, otherwise you will contaminate your acid with excess water, (best to heat it just until the first signs of red/brown appear)

At the risk of teaching people to suck eggs, this sulphuric acid can be used to produce nitric acid, by distillation with sodium or potassium nitrate. :)

[Frunk]

Besides, everybody has access to a glass distillation setup.

Beer bottles. For a 60*C distillation, thermal dilation is hardly a problem.

Some plastics take nitric well, but you can use three beer bottles, a drill press, a set of taps (the threading stuff kind, not the sink kind) and teflon tape to make a distillation setup.

One beer bottle acts as the condenser, while the other two are the distilling/recieving flasks. There's a variant that uses the larger wine bottes.

If you have a torch capable of melting glass, blow those beer bottles into glass pipes.

[Emil]

I was just browsing through the net last night, and came across something I hadn't noticed before. The Hydroponics shops supply Nitric acid at a 38% concentration as a pH down product for use in areas with really hard water.
It's pretty cheap as well, the cheapest I found was £4.50 for a liter.

This could be a really handy source. To get the HNO3 to around a 68% concentration you can literally just distill it away from the water.
And then if you wanted to take it further, (90 - 98%) just distill it with some
HS2O4, or other dehydrating agent.

The second method on a large scale may not be so profitable in the long run, as you could probably synthesize via the xNO3 and HS2O4 method which would be more economic. However, if you can make plenty of use out of the 68%, which we all should be able to (HDN, NG etc), then it could be a handy little source.

Some of you guys may have come across it, but just thought I'd share for the ones who haven't. I won't bother giving a link for it. All you have to do is just go onto the Hydroponics page that you use and just search it.

[Charles Owlen Picket]

Personally I don't think that all that cheap....but you are correct - it would work. But from my perspective if you have proper distillation equipment; proper glassware - using H2SO4 and a solid nitrate would be a less expensive route, no? Now, if you can't get any sulfuric at all I could see it but only if you were to knock out a large batch at once and save the labour.

[Emil]

Well personally you probably wouldn't, but don't forget, I live in the UK. That price is actually pretty good for me. I imagine you are a USA resident, and therefore get decent and reasonable prices. However, in the UK we get ripped off with pretty much everything haha. Just have to put up with it I suppose.

But sometimes it's best to disregard price right..???
I mean only to a certain extent, beings as we are home experimenters and aren't planning any major usage, at least I hope not?

But of course on a bigger outlook, price is very much important.

I just thought this could be a handy source for 70% nitric acid, as for alot of experiments there is no need to go wasting 90%+.
Next on my list is to invest in a glass distillation kit from united glass tech.

[Charles Owlen Picket]

It -=IS=- cheaper in the States but even though I would have no intention of hoarding some voluminous amount the lower cost makes the experiments a more ready, less pressured past-time. Where I am going with that is that if I think I learned what I could, I would just use the material for drain cleaner - with no feeling of monetary loss.

However, if all I could get would be lower concentration I would still distill it down as 90% + HNO3 is so damn flexible experimentally. Being realistic I suppose it's not THAT expensive (4.50) but I wouldn't think I paid 4.50 per liter but 4.50 for 200+ ml....

I know that the UK has a metal plating industry, does it not? THAT'S where acids (technical grade) are used in abundance! Perhaps you could check that out and get the deals we get here. After all the raw materials can't be THAT inflated (no?)

[Emil]

Yes this is a very good point, maybe I should take a look round some companies and try and obtain some acids in decent quality and strength.

I've tried before just buying from a chemical supplier I use occasionally, however, they didn't want to supply acids to a domestic customer.
If I had a business to buy products through they wouldn't blink an eye.

But chemical suppliers are always going to be more careful than a lot of other suppliers, so maybe I'll just have to try some metal plating companies.
If not just have to do things the hard way with the good quality drain cleaner.
The only thing that puts me off trying to obtain some fuming nitric acid is that it is pretty renowned for making explosives, and could leave an all to suspicious trail.

[Charles Owlen Picket]

I have spoken with many people (mostly younger fellows at university, locally) and from my understanding unless one does something quite "attention getting" the idea of having or leaving a "trail" is a fear one need not have.

A few years back in the US the Consumer Products Safety Commission (CPSC) got a hold of lists of buyers that had frequented pyro suppliers and sent them all a letter. It was written on Justice Dept. stationary and warned of not making large exploding fireworks. A low trick, meant to frighten: which it did!

Many people promptly got out of the hobby. But more of them banded together and gave monies to law firms protecting the companies from CPSC harassment. The result was that the larger companies are still in business (albeit with strong stipulations of what they may sell to the unlicensed public).

There are ways to enjoy hobbies such as energetic chemistry without breaking any laws. One simply needs to be creative and careful. I personally, go to a local university and have an individual who is enrolled, do some research while I am in attendance. I enjoy the lab, maybe take some pics and the material is promptly flushed. I live in books on the subject and that fulfills a lot of my wanton desire for "hands on" experimentation.

Reading the law carefully; I am generally safe from harassment as research allows some small level of synthesis if certain provisions are met. The material is not used for noise making or attention getting maneuvers :-) I'm confident you can do the same if you study the issues involved. If you wanted to experiment further, make sure you don't disturb the public with noise or fire. Think safety and no one will be angered.

[Lewis]

This may seem like a relatively simple concept, but I haven't run material covering it here.

I recently bought a full 24/40 ground glass setup, and I'm eager to create some HNO3 with it. I have everything I need, save a vacuum source. This is the last hurdle and it's proving challenging.

I originally thought of an aspirator solution, with the water from the cooling circuit also going through the aspirator. I then began to wonder if a simple hand pump system would be adequate to create a vacuum.

Is it necessary to apply constant suction to the distillation rig? I don't see why it would be, as once the vapors begin to condense, they will counteract the rise in pressure from the initial boiling.

Of course, no system is perfect, and even discounting leakage, there will probably be some compounds (NOx?) that will build up in gas phase, and increasing the pressure. Still, could I simply give it a few manual pumps every once in a while to maintain the vacuum?

If this idea is not workable, I'd like to hear why. Perhaps someone would be able to fill me in on exactly how an aspirator system works as well.

[ChippedHammer]

Your manual hand pump will not last long, I am told that aspirators are second to a proper teflon vacuum pump.

[Emil]

A vacuum on your HNO3 rig, is probably the biggest pain you will come across. A vacuum pump, possibly teflon for chemical resistance, is really the best way forward. However these are expensive.

I bought a chemicaly resistant vacuum pump, and already am having problems. Regardless of what vacuum pump you have, the HNO3 reisdue is still a pain for most pumps. If it doesn't corrode it, is usually makes parts stick. The way forward is to build yourself a filter for your vacuum pump. This way the fumes that go through your pump, are not half as nasty as they are before the filter.
I can't say how well a hand pump will hold up, maybe if you have a good filter it might not be such a problem.

Personally I would choose an aspirator over an expensive pump anyday. Why?? It does exactly the same job only at a fraction of the price. An aspirator works by simply creating a vacuum from the resistance of the liquid or air flowing through it. The water comes in at the top of the aspirator, which then hits a narrower exhaust port which is at the bottom of it. This resistance causes a vacuum which comes off from the side of it. You simply connect this to your rig via a tube.
There is no maintenece needed with them and nothing which can really go wrong. The HNO3 fumes are just washed down the drain with the water.
Of course you need a mains pressured feed to attain a decent vacuum which could be a pain, depending on your location of your lab. If you have a mains pressured tap near by... Excellent!

There can be a slight drawback with these aspirators though. If you water pressure from your tap or feed drops whilst in mid lab, it can sometimes cause for water to be spat out through your vacuum tube, diluting your nicely distilled fuming nitric. This isn't a worry as long as your pressure is pretty consistant, which it should be.

[Lewis]

Ah! So the aspirator needs a taper. Having only seen the outside of them, I attempted to use a regular "T" of tubing for mine. :p

I'm planning on simply recirculating the water with a bilge pump and reservoir. Hopefully any fumes will be sufficiently diluted so as not to wreck my equipment.

I suppose the higher the speed of the water aspirator, the better the vacuum up to a certain point? If this is the case, then my crappy little pump probably won't do it.

[Emil]

This is indeed true, for the cost of an aspirator they just aren't worth trying to improvise and build yourself. A guy sells them on eBay, who is based in the US. I think he sells them for around $20, although you could probably pick one up for cheaper.

Yes, this would probably be the best way to go about things, recirculating the water is ideal, as you will be amazed how much water you are wasting otherwise. Wasting it isn't the problem, it's mainly the cost. The higher the water pressure, the better the vacuum will be up to a certain point yes. So if you can create a loop system with a pump, and pressurise it to a decent pressure, you will be well away. I can't give any exact figures, all I know that mains pressure is usually 3-4 bar, some areas may be more or less. This allows you to easily pull a sufficient vacuum for this type of distilllation. Even half of this pressure would be enough for a decent vacuum. Remember with HNO3 we only really need to lower the boiling point a smallish fraction to avoid decomposition.
Make your system large enough, in the sense of the amount of water it can hold, and the fumes will not be able to concentrate the water enough to cause any harm to components

I was bummed a few months ago. I had a lovely all glass aspirator, which I accidentally snapped at the stem where it thins. I was not impressed.

[megalomania]

Eek, you need a trap for your vac pumps to avoid this. At the very least pull your nitric acid through some water, and then pull that moist air through a drying trap. You can use many materials to DIY a washing and drying trap, flasks, mason jars, beer bottles, PVC pipe. Choose your material depending on how strong your vacuum is.

Dissolve some baking soda in your water trap to avoid it becoming acidic as well. The base will neutralize the nitric fumes as the air is drawn through.

I used to have a problem running distillations with my aspirator since both the water line and vacuum line had to run from the same device. I needed the water to circulate through a condenser, which can only take so much pressure, which in turn means weak vacuum.

[Emil]

Ahh yes Mega I was just about to say about the water having to feed two devices. It has to feed your aspirator and your condenser, thus lowering your flow to the aspirator giving you a weaker vacuum. Here's the trick though for anyone who might be having this problem. Put an inline isolation valve before the condenser flow tube. You can purchase one from any plumbing store. I made my water tubing rig out of 15mm copper tubing and then used tubing to transfer from the copper to the rig. This way you can regulate the pressure on the condenser and turn the valve almost fully off. Just allowing a slight trickle of water through the condenser still keeps it ice cold, but doesn't kill off your pressure to the aspirator. This way you can keep your vacuum pull high.

I am currently making a trap for my pump, this way it saves the sticky residue clogging the bits on your pump up. Luckily mine is a chemical resistant pump, so it doesn't damage anything, just makes an annoying cleaning job after every distillation.

[ChippedHammer]

How many people here have heating mantles? I'm leaning towards getting one due to the sheer simplicity (no annoying oil baths) of them.

I know there are two diffrent types, thermowells and Unimantles. So far I'm leaning towards a thermowell as you can directly pour sand into them and they seem to last longer (or so I'm told).

[Emil]

I went for an electric hot plate to start with, it has a built in magnetic stirrer aswell, which isn't the most powerful, but it can help alot. I never really thought much of the hotplate.

Personally I prefer using a flame. It's quick to ignite, fast to ajust, and can be done very cheaply. A bunsen burner fed off LPG would be good enough. I personally lack space so do not need a huge cannister of LPG gas laying around, so I chose to go with a camping stove fed by small gas bottles. You just change your gas bottle over when it runs out. They last for a fair while too. Dont about 4 distillations and am still on the same bottle.

An oil bath is completely unnecessary if you ask me. I Don't see the advantages of using such a system. More hassle than is needed.

[ChippedHammer]

Using a open flame is bad for your flasks, hot spots form which stresses the glass and results in uneven heating. The only glassware that should be exposed to a flame is a test tube and then its passed in and out of the flame.

[Setharier]

I have an lab torch which fire emitting holes are drilled around the head so they spread around evenly, making no single hot spot but heating about the whle bottom except the very center.

Althrough I am able to obtain pure new 2kW heating plate only for €20 and attempting of purchasing it very soon, is it "much" better than the lab torch? Only cons I can find might be the relative high energy drain and ability of elevating the distilling flask directly in contact with it.

[Emil]

Using a open flame is bad for your flasks, hot spots form which stresses the glass and results in uneven heating. The only glassware that should be exposed to a flame is a test tube and then its passed in and out of the flame.

With a bunsen burner yes. But I use a camping stove, which has a wide ring and spreads the flame out nice and evenly. Besides the heating for the distillation of nitric acid is relitively mild. Especially under vacuum as it should be. It's not a problem for this task.

[Combustable Wishes]

Using a open flame is bad for your flasks, hot spots form which stresses the glass and results in uneven heating. The only glassware that should be exposed to a flame is a test tube and then its passed in and out of the flame.

As true as this is, and the viable solution of distributing the flame via a splitter, iIbelieve the use of a ceramic material between the flame and the glass is almost a better solution as it evenly disperses the heat everywhere it touches. I am by no means an expert, but that is what my AP chem teach trusted us with to heat beakers, and if I managed not to break something that way (natrual klutz) it seems pretty viable.

[jarynth]

Hey all, this link provides a concise diagram of the azeotropic properties of the HNO3/H2O mixture depending on the amount of H2S04 added:

http://www.qvf.com/en/processsystems_3/mineral%20acids/ConcentrationingofNitricAcid.shtml

The data probably refers to standard pressure. I'm still looking for a graph detailing the concentration of NA vapor at low pressure, when I find it I'll let you know. Many older handbooks report some data in table form, and the missing info can be obtained by clever interpolation, but an easy-to-use reference for the impatient amateur chemist is advantageous. =)

[DetaDude]

General info. Lab depot sells a Nalgene aspirator (plastic) for around $12.00. I have three of them on my distillation set up and can select 1, 2, or all three. They are fed by a clear water pump from Harbor Freight and with all three opened up and pulling vacuum the pump is making 40psi and the vac. is 29.5 in.hg., if I bleed off a small amount for the condenser, I still have 30 psi and a vacuum of 28 in.hg..The pump draws from two 5 gal. buckets , and when distilling I put a 10 lb block of ice in each bucket. I do not have running water in my lab at this time but its coming soon.

I recently added a third bucket and a submersible aquarium pump to handle the condenser chores.

A quick note on some glass aspirators sold by Pellet Labs (AKA Mt. Home Biological) I have tried these ( I have three of them) seems the problem with them is that when the vacuum get above 16 or so in. hg. the drain water starts to back up in the venturi and cuts off the vacuum, they are nice units if you keep th water pressure low and are willing to accept a lower vacuum.

I also use a teflon hose for the vac. outlet from the still to the first stage filter/trap in the vac. circuit , be sure to add a bleed down valve between the still and the first trap, so when you shut down operation you don't suck neutralizer back into your receiving flask.

I do hope all of this is of help.

If I can help further please contact me via PM.

[Lewis]

Deta: Thanks for the advice! I'm nearly set up to do my first run at HNO3. It's been a long time in the making, but I'm taking my time, with the intention of doing it spot-on, the first time around.

I'm not too concerned with pulling a torrential vacuum for this project, as even a mild one will do wonders on eliminating NOx fumes when distilling.

With something like nitric distillation under vacuum, the home experimenter would probably do well to go the extra mile with preparation and safety. While I'm almost ready to begin (still waiting on a glass aspirator), I'm still divided on a few things, namely:
-What sort of tubing to use for vacuum gauge and aspirator lines
-How to stop moisture from entering the still
-Finding a good storage solution for high concentration HNO3
-Sealing my ground glass joints properly

Whatever I decide to do, you can bet I'll document the process, who knows, maybe someone will even find it useful!

[fractional distiller]

Hey Lewis I have a Few suggestions for your process. You do not need to follow any I am just spouting a few out.

What you are aware of is that the Nitric acid is going to attack many kinds of tubing. My best guess would be to use a Nitrile type tubing that will be somewhat acid resistant.

There are also special purpose vacuum tubing that can be purchased from any chemical supply shop. That being said you will most likely have to purchase it online or grab a bit from your local chem lab.

What you should do for your ground glass is just get yourself a acid resistant grease for the joints then pull your vacuum with your aspirator via the sink try an venturi valve if your need a higher fluid speed.

Attach the venturi to the sink. Attach aspirator to venturi use a glass tubing that can be bought @ www.unitednuclear.com for the glass simple bunsen burner can be used to bend the glass then needle nose pliers can be used to attack the glass to the aspirator once the glass tubing has been heated just flare it with the tip of plier place over it and then clamp down. Flame polish it as cooling to deal with thermal shock (glass will still be brittle due to lack of proper annealing, will work in your favor for removal). Your aspirator will take the NOx fumes with it down the sink.

As for the the moisture use a simple cold trap. Set one up using a large test tube or other device by attaching a glass tube to it and seal it and then place inside a larger container fill with any Hydrocarbon and dry ice. (any contact with dry-ice hydrocarbon will cause instant frost bite) but this will deal with the moisture by freezing it. Instead of using the aspirator to rid yourself of Nox also vent it through cold trap as well.

If not use Higher concentration H2SO4 to take care of moisture because it will be diluted into the acid creating a little heat as dilution of H2SO4 is exothermic.

Storing your acid is easy buy or (come by) a large brown 2 liter bottle (aids in protection of UV) fill it with your acid and keep in fridge of freezer.

hope it helps

[Lewis]

Fractional, I'm a little confused by what you are referring to when you say a water aspirator connected to a venturi. I was under the impression that they were the same thing.:confused:

I read mention of needing grease/tape on ground glass to make a decent seal constantly, but I still have a hard time believing it! The joints just seem to fit together so perfectly, not to mention the fact that a decent vacuum would pull them together even tighter.

I'm a firm believer in using the proper equipment for the job, but I still hate spending a fortune and waiting for things to come in the mail. I'm wondering how fast stray nitric/NOx fumes are going to destroy conventional aquarium tubing (I'm assuming quite fast).

I also would love to avoid dry ice whenever possible, as I don't think it stores well even at freezer temperatures. I've been leaning more towards a trap filled with dessicant.

[Alexires]

Lewis - You could always try PTFE (Teflon) tape on your joins. Just a small amount (a couple of layers) should help hold the vacuum as well as be resistant to the acid.

[totenkov]

Yes most recommend some kind of Teflon grease for the joints. In most distillations, I have never bothered. When you are going to distill Nitric just connect all the joints in the sequence that you want (I have tested a few different connections in the glass, to develop efficiency). Then wrap the connections with generous amounts of Teflon tape, from the hardware store.

Not only will this rig avoid leaks but the tape will hold firm the joints, should loosening occur, which it does. Some ill fated glass of my own has met its demise that way, double and triple check every time!

[Emil]

Lewis.

Like the others said, teflon (PTFE) tape is definately the way to go with sealing the joints. It is necessary to seal the joints either by means of tape of a vacuum grease. Not only does it properly seal your rig, the most important thing is that is allows your glass to come apart alot better after you have finished the lab. You'd be suprised how well those glass joints hold together at times, and you don't want to risk damaging the glass when just simply taking it apart.

Dow corning sell a vacuum grease which is deisgned for this application, however is it resistant to nitric acid vapour? Absolutely not.
This is where teflon tape comes in handy as it is also dead cheap. The problem with vacuum grease is you also risk the chance of slightly contaminating your nitric acid as it will most likely attack it and then end up being carried over with your distilled acid.

The tubing question debatable. Depending on what specific material it is made from depends how it copes. My tubing I use does not resist the nitric vapours either, but it only turns the clear tubing yellow, it doesn't really deteriorate the tubing itself. I would just use the aquarium tubing and then inspect what happens. If it is only discolouration then I wouldn't worry. The correct tubing can be very expensive to buy aswell so unless really needed, I would try and work around that.

All that is needed is an aspirator for your vacuum source. A glass aspirator is great. I have a metal "chapman" aspirator. The spec states that with a water pressure of 2 bar (30 psi), a vacuum of 29.5 in/hg can be expected. That is pretty damn respectable as 2 bar isn't much at all. You can guarentee any mains water is going to be more than that.

[Lewis]

Well, the aspirator is in, and as luck would have it, when attached to the bilge pump I've been using, it won't create even a weak vacuum with it.:(
It definitely works like a charm with enough water pressure, I just don't have the means to create it as I don't have a water line out to the lab. I'm going to have to get inventive...

I did notice is an old air compressor sitting in the corner. I wonder if it could be used to move water somehow...

[Cobalt.45]

I did notice is an old air compressor sitting in the corner. I wonder if it could be used to move water somehow...

FWIW, Harbor Freight sells a cheap (~ $13 + S&H) air vacuum "pump" that will pull a vacuum w/your compressor.

More: http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96677

[Lewis]

It seems like a good deal, but I already have the venturi so I'd rather improvise something myself. Also note my location. If I'm outsourcing my supplies anyway I might as well stick with a system I know is going to stand up to the most corrosive of fumes.

I'd be curious to know what's inside that device. For that price it seems like it could be easily improvised, but I've been wrong before...

[Cobalt.45]

I'd be curious to know what's inside that device.

Think of a simple venturi w/a tap near the narrowest portion of the "throat".

On closer inspection, it has a zinc casting as the main portion of the device, so would be impractical if exposed to HNO3 fumes, etc.

[Lewis]

I spent most of the night trying in vain to get a decent vacuum for my distillation setup. Simply put, the fancy glass venturi I bought can't create a vacuum worth shit.

I built the still in the back yard so I could access the water hose. Even at full blast (I was almost afraid the fragile looking aspirator was going to explode), it created only a meager amount of suction. Not enough for my gauge to read anything above 0 in. Hg.

Below are the pictures of my failed attempt at distilling some water under vacuum:

http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1497.jpg?t=1218602070

http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1495.jpg?t=1218601917

[Emil]

Lewis here is an idea. You may have tried already so if you have then please forget this.

Just connect your aspirator up to the water hose and then where the vacuum take off is on the aspirator, place a hose and connect it directly to your vacuum gauge. This doesn't include any other part of your still. Now turn the water on and inspect what happens. Does it pull any vacuum now?? I say this because incorporated in your rig, is plenty of joints and possibilities of leaks for the vacuum. Maybe the reason you are not seeing any vacuum is because your still is not holding it???

Just do this as a basic check, this then eliminates any worry about problems with the rig. If you still recieve no vacuum then you have a problem. It is either your vacuum gauge isn't working right, or your aspirator isn't.

Later on this evening I am actually going to test my new metal aspirator via the same means that you have. It will be hooked up to my outside water hose and then a vacuum gauge placed on the off take to measure the vacuum it produces. I already know the water pressure of the outside hose is 2.2 bar. It would be more however the connection from the mains system incorporates a flexi hose which is somewhat restrictive to water pressure. After I have checked it and recorded the results, I will post again and let you know.

I did have a glass aspirator, it looked the part, but it was pretty useless in the fact is was so fragile. When disconnecting the quite tight tubing one afternoon, the stem of the aspirator cleanly snapped. It was right where it thinned down. I choose from that point never to get a glass one again and go for something ruggid. I will be checking this later and report back.

[Emil]

Well I have done those small tests now and have some answers. I would of edited my previous post rather than repost but it wont let me?

Anyway, after my putting my new aspirator to the test I was happily suprised. The unit pulled a really good vacuum at just below 30 in/hg.
Take a look. This is what I recommend you to do with your unit Lewis.

Here you can see the Aspirator connected up to the mains, and the vacuum gauge connected to give me the reading.
http://i250.photobucket.com/albums/gg256/emil2008_2008/P1000130.jpg

A close up on the gauge. Note the in/hg at the top in white measuring anti clockwise. Ignore the fact the needle is reading off the meter. The gauge for some reason sits at 3 in/hg when disconnected. It is merley a fault, so with this gauge I just take off 3 in/hg to get the actual figure.
http://i250.photobucket.com/albums/gg256/emil2008_2008/P1000132.jpg

Now time to look at my actual vacuum pump. This is a chemical resistant one. Quite a nifty bit of kit. Here is the same, connected up to the gauge for a nice reading.
http://i250.photobucket.com/albums/gg256/emil2008_2008/P1000134.jpg

Close up showing 26 in/hg (take away 3 and this is 23 which is actually listed in the specification documents).
http://i250.photobucket.com/albums/gg256/emil2008_2008/P1000135.jpg

This just shows you that the aspirator actually out performs the vacuum pump. Obviously for most people the consumption of water with an aspirator is enough to cause a problem.

If you are still having a problem after you check your aspirator, then I recommend to take the item back from where you brought it for a refund. Then buy one of these. A chapman aspirator from a lab shop on eBay. Nice price. Heres the link.
http://stores.ebay.co.uk/AVOGADROS-LAB-SUPPLY_FILTRATION_Aspirators-Vacuum-Pumps_W0QQcolZ2QQdirZ1QQfsubZ3452369QQftidZ2QQtZkm

See how you get on!

[Lewis]

Turns out the aspirator works after all. I was having difficulties last night for a couple reasons. Firstly, the check valve on the unit tends to stick in place once it closes off from positive pressure. Secondly, the aspirator seems to not work when the water flow is turned on, and THEN the vacuum line is attached. The whole thing needs to be assembled before the water is turned on.

[Lewis]

On another note, I set everything up again and distilled some water the other night, but still could only get about 5" Hg out of the rig. Might be fine for nitric but I'll probably look for a better water pump soon.

I tested my stored H2SO4 today and it only had a density of about 1.7, which I calculate to be about 80% concentrated.

Boiling is a complete bitch because it:
-takes a lot of energy
-inevitably fumes up the shop, even if I carefully suck the fumes off the beaker
-gets organic matter in the acid when done outside

What does this forum think about distilling at this concentration? Obviously water is bad in the system, which is why we use drying tubes, etc. to remove moisture from the still, but I'd assume the 20% or so of water would be clung on to by the sulfuric, and thus not be a problem. I would assume that (especially under vacuum) the BP of water and nitric would be sufficiently different to not cause a problem, but this is total speculation.

[Emil]

Concentrating Sulfuric acid is a nasty job, unless you have the correct equipment, like a fume hood.

However, it all depends what kind of distillation you are doing, from your question I find it hard to tell. If you are going to be doing the Sulfuric/Nitrate route to distill off nitric acid, then 80% is not really going to be ideal. It will work but you will end up with a weaker nitric acid which will need further distillation to remove water.

If you are concentrating nitric acid you already have, (which is around 70%) and thus using the sulfuric acid to steal the water then 80% would be fine, You would just have to regulate the amount you add. In both circumstances 95%+ sulfuric is really the best.

[Loveofchaos]

I know this is a bit belated but to me, getting the wax off of the Potassium Nitrate "prills" is too much work for what you get. Where I live in CA you can go the pharmacy and buy pure Potassium Nitrate, US$2.37 for 6 oz. Even though I am not sure it is 100% pure, I know it is very pure. Makes good smoke bombs too =]

[Alexires]

Loveofchaos - Yep, it is so damn belated that I have no idea what you are replying to. Keep your posts on topic and in a nitric acid thread, we don't really care that you can't be bothered doing something because you can just walk down to the store and buy it.

First and last warning.

[Lewis]

My first crack at HNO3 was only very mildly successful, but achieved a result nonetheless. It went like this:

140 KNO3 grams were added in portions to 153 (87mL) room temperature H2SO4. A small amount of red-brown fumes evolved, and temperature rose. The mixture was left to its own devices for maybe an hour, before being heated slowly in a water bath under vacuum.

The rig stayed at a pretty constant 18" Hg throughout. Initially, a fair amount of NO2 evolved, but this tapered off as the nitric began to come over, which occurred at ~74C and at a peak rate of about 1 drop per 2 seconds. The water bath stayed between 90 and 95C, until it boiled off, at which point the flask's temperature began to drop, and the experiment was ended.

I originally tried to use a dry ice/methanol cold trap, but the stopper on the flask continually leaked air, so I opted to connect the vacuum adapter directly to the aspirator. This undoubtedly lead to an inferior product, but it was a trial run anyway.

A better way of heating the flask will have to be used in the future, as well as leaks fixed, etc. Still, I did receive a small (~100 mL) amount of insidious looking yellowish nitric that gave off red-brown fumes readily.

[Alexires]

Lewis - An option for you to use may be to make your own custom heating mantle. If I remember correctly, there is a thread/post around here that mentions it, but basically it involves pouring plaster of paris into a container, sitting the flask that you are going to be heating in it until it starts to hold its own shape, then press some wire into the plaster of paris.

When it dries, apply current and work out what setting you need for various temperatures (try it on water first). Make sure the wires don't touch, etc.

Your leaking joints problem could be solved with a liberal application of Teflon tape. Since the pressure is from the outside, it should push the Teflon into the holes, sealing them up and holding a vacuum better.

Perhaps try rigging some kind of water condenser up to your water bath (just a metal "cover" with a fan blowing on it should do). It will help keep the water in the bath without you having to constantly top it up with boiling water.

[Emil]

Sounds good, maybe just a couple of points though.

Prior to mixing your Sulfuric acid with your nitrate, make sure you always cool your H2SO4 in the fridge for an hour or two. It is always a good idea using acids when they have been cooled. Doing this would of prevented the red/brown fumes that were given off at the beginning. There should only be white fumes given off not red ones. Also, especially with KNO3, you really have to make sure it has been mixed well. I personally hate using KNO3 for Nitric production, but I am well aware of its advantages with being cheap and easily available. I have always found AN to be the best and also Sodium nitrate. You actually have a reasonable liquid to distill rather than a disgusting sludgey almost solid slop which the KNO3 gives you.

Not having a cold trap will not give you an inferior product. This is merley to protect your vacuum device from harmful Nitric acid fumes. Using an aspirator there is no worry as there is nothing to damage inside. A piece of tube straight from your aspirator to your vacuum adaptor is all that is needed.

[Lewis]

As always, thanks for the feedback. Perhaps my leaking joint problem just needs more tape. In the past I've made a very thin layer of tape, never overlapping it more than 2 layers in any one spot. My logic was that the entire joint will contact the teflon better if it is in a consistent thin layer, but next time I may just go nuts with the stuff.

I thought a cold trap helped to condense/freeze any water vapor coming off the aspirator. Regardless, I use an empty flask between the rig and vacuum source now because I got some backflow from the aspirator once I turned it off the first time, diluting my fresh nitric with a few drops of water.

As far as nitrate goes, I have easy access to KNO3 and Ca(NO3)2. Calcium nitrate is dirt cheap, which I like, but I'm not sure about its tendency to from hydrates, so I decided to play it safe.

I think my next purchase might be a nice heating mantle from labX or the like. Maybe an overhead stirrer too. :)

[Emil]

Ah yes the backflow from the aspirator can be a killer. The last thing you want after an hour of hard work is to have it ruined by some damn water.

The mere fact that your rig if under a vacuum is enough to keep any vapour entering it what so ever, so this is never a problem from your aspirator. The problem can arise obviously when you turn it off and suddenly you get the backflow, like you said. Luckily I think my aspirator is an anti backflow one which may be handy. Either this or just keep the vacuum running however remove the tube from your rig before you turn it off.

An over head stirrer could be a very good investment. I have used a couple of magnetic stirrers in the past, always being quite dissapointed with their overall performance. At first I find they seem to work a treat, but as your mixture starts thickening they slowly but surely give up their will to stir. Even with AN, which stays alot thinner than KNO3, it still will not perform after you get so far through it. Stirring it by hand is an absolute nightmaire. Every muscle in your hand and entire arm start to ache by the time you have finished lol. Only problem with the over head stirrers is they seem to be reasonably expensive, and I'm not sure how well they work??? Do you have any idea?

[fluoroantimonic]

I really don't think there is much of a need to bother with a vacuum when distilling nitric acid. As far as I know it has been conclusively determined that using a vacuum when distilling nitric acid from XNO3+H2SO4 is usually useless if not harmful. It will only slightly reduce decomposition, while it lowers the boiling point making condensers less efficient and pulling more water from the sulfuric acid. As far as I know the only reason you ever really need a vacuum for nitric acid it to remove the last traces of NOx from 99% nitric. Don't believe me? Read these threads (especially posts by garage chemist):

http://www.sciencemadness.org/talk/viewthread.php?tid=9450#pid109960
http://www.sciencemadness.org/talk/viewthread.php?tid=1851#pid55116

an interesting alternative idea
http://www.sciencemadness.org/talk/viewthread.php?tid=2823#pid30627

Hope this helps clear things up a little.

[Emil]

I don't use Sci madness, I might browse through there every few months, but I have actually read those threads on nitric acid. He does have some good points however he seems to think it is not possible to obtain anhydrous Nitric acid from a single distillation which in fact not true. If you are using high quality enough H2SO4 (98%), and you make sure that your nitrate is completely dry (dried in oven prior to use), then you can obtain anhydrous nitric from a single distillation. If this is the case then there isn't any water to draw from the H2SO4, only extremely minimal which in this case doesn't matter.

But it is a good idea though, if you are using slightly lower quality products where more water is present, you are not going to be able to produce anhydrous nitric in one hit. The best thing you can do is to produce the highest concentration nitric in your first distillation, then if you are striving for a really pure product which is only really needed in RDX manufacture, resdistill it with the equal volume of Sulfurc acid to steal the last water. A vacuum certainly is needed for the second and last distillation, otherwise you end up with a fairly strong yellow HNO3. Believe me. A slight yellow tint is ok, but really as clear as possible is always the desired product.
RDX really is that fussy, water or nOX is a no no, and nOX is always going to be produced at atmospheric pressure no matter how careful the distillation is carried out.

[Lewis]

Interesting points. I distill under vacuum because I can. I have a few reasons for this, namely:

-I don't use a very powerful vacuum, so the change in H2SO4's tendency to trap water is minimal.
-The aspirator prevents toxic and corrosive fumes from entering my poorly ventilated workspace.
-The vacuum lowers the amount of heat needed to distill, which saves time, energy, and unnecessarily heating the shop in these hot summer months.

Emil: On the topic of overhead stirrers, I admit to knowing next to nothing about them. I assume one would come in very handy, knowing that not many heating mantles have a magnetic stirrer in them.

[fluoroantimonic]

Of course you can get anhydrous HNO3 from a single distillation, it just takes tons of conc. sulfuric. I think he's saying that its a waste of high quality sulfuric acid, when you can use low quality dilute acid and save your concentrated stuff for a second distillation to dehydrate the nitric acid. Or not use conc. sulfuric at all and break the azeotrope with something else. In any case I know garage chemist knows what he's talking about, I don't believe I've ever seen anything be very high quality information from him.

I have to admit using a light vacuum to keep the vapors at bay is a good idea. Even so it seems like a lot of screwing around for such a benefit. What are you using the condense the nitric? I would imagine the extra effort and cost of more effective condensation means (not to mention the vacuum itself) would out way the (very small) energy cost.

[Lewis]

I use a ~45cm Liebig condenser, and believe me, the vapors are in no danger of passing through it without condensing. They are eliminated completely in the first 8th of the condenser length!

It could well be that the vacuum is worthless in many regards, but frankly until I get a better heat source it really helps. My nitric distills painfully slowly even at my kitchen hot plate's maximum setting when I use a sand bath. :( This really is the only reason I'm not pumping out tons of high quality nitric for many fun-filled energetic experiments. I simply do not have the many hours necessary to make nitric by distillation at the current rate.

Insulating the flask and adapter with Al foil helps somewhat, but it's still such a tedious process, not to mention one that I feel for the safety of my property I should be watching constantly.

[Emil]

Do what I did and turn to the direction of the sinister yet friendly flame. You can't beat it. So much more control over heating, and you can kick it up as high as you need. I can distill quite rapidly when it is all set up right. I haven't timed it (yet) so I cannot give an accurate number, but with the prior mixing and messing around aside, in an hour or two, I could distill a litre of fuming nitric acid. I'm not sure on heating plates and such.
Mine never used to really satisfy me. My first test use with it was a 500 ml beaker filled with tap water. I turned it on, it was baking hot, and yet the temperature of the water was hardly rising much. It took ages and ages to start to get the water to any "hot" tempterature and even then it wasn't boiling. I was put off by this and decided to buy a portable camping stove which has a wide ring on it for the flame. This way, no cracked glass, and plenty of fast reliable heat. Besides with the price of electricity so high, I believe it is much cheaper to use a gas based fuel.

I use a 2000ml boiling flask and a 500ml recieving flask, which is soon to be upgraded for another 2000ml. A 600mm condenser and the necessary adapters to connect the rig up. A Vacuum pump or an aspirator feeds the vacuum needs.

To me the distillation with a vacuum, even if it is just slight, makes the process run a whole lot better. Like stated your fumes are just disposed of, and it seems to speed things up with a nicer margin for decomposition. I have distilled without vacuum before, and I can tell you, it is alot slower, you have to regulate and mess around with the flame settings a great deal more, and you end up with dark yellow acid.

I can understand the economical drawbacks with introducing the vacuum. Let's face it, you add a water aspirator, you use alot more water which costs. You buy a pump and you have obviously used a fair amount of money for that. Unless you ghetto rig yourself something out of some old bit of junk kicking around the garage (which will probably end up just breaking anyway), it is going to cost you. However it is an investment which is based upon your personal situation. Planning on making nitric acid insmall amounts a couple of times??? Forget it. Plan on making high quality nitric acid more often, absolutely.

[bloodhound125]

Does anybody know where I can find a HNO3 concentration chart like the one used by the ragheads in that famous HNO3 video where they make the acid in a stainless pot with nothing but latex gloves, I think someone said its on the FTP. I basically want to know what the concentration of my acids are according to weight and temperature if this is indeed possible. Thank you

Moderator Note: I have approved this post because it was posted in The Watercooler originally and I could not find the answer to his question.

[Emil]

Most people will usually just say UTFSE, but in this case the charts are actually quite hard to find. Not sure why, but I'm more than happy to post them up for that reason.

Nitric acid concentration chart.
http://i250.photobucket.com/albums/gg256/emil2008_2008/hno3.png

Even though this is a Nitric acid thread, I feel that it's equally as useful to have the Sulfuric acid chart aswell.
http://i250.photobucket.com/albums/gg256/emil2008_2008/h2so4.png

Very handy charts, no matter what type of units you work in, the chart gives details for all. Don't have a hydrometer?? Not a problem either because you can simply just weigh your nitric using the "grams per litre." Even if you only have 250ml of product, just do the necessary maths.

[Lewis]

Those are indeed handy charts, Emil. Still, one thing about them confuses me. What does 20ºC/4ºC mean?

[megalomania]

Those temperatures correspond to the density of water. The two temperatures are, more or less, room temperature in the case of 20, and the maximum density of water at 4 (water occupies less and less space to just under 4 degrees, after which it expands). I am not positive what the scale in the chart means exactly, but I suspect it may be the density of the mixed acid at 20 degrees factoring in water density at 4 degrees. I see there is an asterisk after the entry, maybe it explains it there, but the meaning of the asterisk is not in the pictures Emil gave.

[Emil]

Yeh I think Mega is correct, I would like to be able to confirm but am unable to do so due to not being able to find the source where the damn charts came from. I think I got them from a site which I see mentioned here at RS. All I can seem to remember is that the guys name began with F, and had his own site which is where these charts are from. I seem to remember he was fairly well known to certain members.

Anyway I would go ahead and measure your density at 20c. This seems to be the default temperature for most measurements including viscosity.

[stupid939]

Yeah, that was Frogfot and his site was frogfot.com, but its down now. I was going to see if someone here had a backup of his site, but I will get to that sometime else. I had a backup, but my external crashed.

I did find another list which will work:

http://img523.imageshack.us/img523/7554/nitricbm3.png

Its at imageshack, so I would download it and store it somewhere before it is taken down.

[Alexires]

stupid939 - Thanks for that, it will be very helpful.

[DetaDude]

Both charts appear to be from the Chemistry/Physics Handbook quite likely an older version, both charts look very much like the ones in my older version of this publication.

[Lewis]

I feel it's time to come back and show everyone where I'm at with this project, after all the helpful advice I've gotten from this thread. Last night approximately 50mL of HNO3 was distilled in an experiment to get the maximum concentration possible in one pass.

A large excess of H2SO4 (140 mL) was used in an attempt to trap as much water as possible. The nitrate salts used were 120g KNO3, and 20g Ca(NO3)2.

The H2SO4 was pre-chilled before the salts were dissolved. Some heat was generated, but no noticeable NOx fumes. An apparatus for vacuum distillation was set up, but it was discovered too late that the untested PTFE thermometer adapter fabricated earlier leaked badly. As a result, only a feeble 5" Hg could be maintained in the system. (just enough to safely pull off nitrogen oxides for dilution)

The reaction flask was heated gently for just under 2h, with the majority of the distillate coming over at 71ºC. Eventually, the temperature began to rise again, until the heat was removed at 78ºC.

While a preliminary assessment of density placed the HNO3 in the ballpark of 1.5g/cm3, the volume measurements used in the calculation were not accurate enough to determine the concentration of the acid. (It could in reality be anywhere from 80% to 100%)

Here are the pictures:

http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1710.jpg?t=1226698828
Prepping the rig.

http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1709.jpg?t=1226698930
Dissolving the nitrates.

http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1716.jpg?t=1226698992
Heating reaction flask.

http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1714.jpg?t=1226699040
Close up of vacuum inlet and trap. The rubber stopper didn't stand up well to nitric acid vapours.

http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1722.jpg?t=1226699138
Reaction flask.

http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1717.jpg?t=1226699165
The pumps supplying water to the aspirator and condenser. The aspirator pump is a big electric waterfall supply, while the condenser uses a small bilge pump.

http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1730.jpg?t=1226699239
Storing the new HNO3.

This is inconclusive as I obviously cannot determine the concentration without better volumetric measurement or different equipment/diluting the acid. Perhaps the next experiment will be to try RDX out for size.

[Emil]

Very nice Lewis. I like the set up you have there. I also invested in one of the vacuum gauges that are meant for cars as well, handy little things to just keep an eye on your vac throughout.


Good idea on the PTFE thermometer adapter, it's just a shame it was letting by. It is handy having the thermometer but really not mandatory. If this is giving you problems I suggest investing in a proper adapter or just doing away with the thermometer and plugging it off/changing the fitting. I don't use a thermometer on my setup. I don't really see any need in this instance. The nitric will boil when it wants to boil, according to vacuum etc. So regardless whether it boils at 50c or 75c it just seems unimportant info. What I do is heat the mixture up slowly and then just leave it at a slow boil. Adjusting the temperature very slightly to get my preferred rate. I can distil quite fast because I have a vacuum source which pulls 25-30 In/hg. This means breakdown of the nitric is very small. I don't have an exact rate at which I distil but I would say at least 3 drops a second.

One thing I did note is that you seem to be mixing your HNO3/Nitrate mixture in your round bottom distillation flask. This would lead me to believe that stirring is minimal unless you arer using a magnetic stirrer??
Mixing of your initial mixture is very important I find for a decent result. Make sure as much nitrate as possible is dissolved and this is why I tend to mix mine in a normal flask which allows me to really stir it well.

I find the magnetic stirrer to be of use about 2/3's the way through the mixing, after that is seems to just come to a stop as the mixture really thickens up. I don't imagine a magnetic stirrer working if your using KNO3. The couple of times I used KNO3 as my nitrate, I had trouble stirring it by hand! It really got that thick. AN is my preferred choice now.

I notice you have an extraction duct. This is the next thing on my list. Can I ask whether it is hooked up to a fan to withdraw the fumes, or is it merely just acting as a guide to let the fumed float out of the window??

This is just a tip as for the RDX comment you suggested. I once thought I'd give my 80-90% Nitric a go for making it. It was yellow in colour and had only been distilled once. Let me tell you it was a waste of time. Don't get me wrong you will get some RDX, but the yield suffered so bad. I think I used Mega's route (330ml Nitric and 75g Hexamine). From this I got about 10-15g of RDX after washing and filtering and drying. I followed all instructions to a perfection, and the obvious flaw in the whole thing was the quality of acid. So, Unless your Nitric acid is clear, and 98%+, don't bother wasting your precious acid and Hexamine.

However it is very simple to acquire such a fine grade acid. Take your 80-100%yellow nitric and add to an equal mass of concentrated Sulfuric acid. (both acids cooled in the fridge may I add). You may find a temperature increase so use a light cooling bath to keep them under control if necessary. Distil this in your rig, However you are now looking for a decent distillation which produces next to no NOx, so this calls for your 20" Hg + vacuum now which your aspirator is quite easily capable of. You want basically no breakdown or colour change. A slight tinge of yellow is acceptable, as this can be removed. Now your acid is ready for RDX.