Some interesting reactions - Archive File

[megalomania]

pete
Frequent Poster
Posts: 56
From: u.k
Registered: JAN 2001
posted 07-01-2001 07:14 AM
--------------------------------------------------------------------------------
I have had a lot of time on my hands of resont, so i thought that i would do some of those interesting little reactions that you often think about, but never dream of. First of all, aquiring white nitric acid, to get over about 98% pure nitric acid then you are going to need the dreaded vacumn, but white 98 % is possible, without urea from conc red acid. Some time ago i prepared a small amount of red nitric acid, i but time in a beaker, and went to get other materials. When i got back i noted the acid was clear, what the hell. I poured it into a container and checked its density, which indicated 98 % purity, which is what i tend to get with my red nitric acid. I took some more red acid and did the same trick, a shallow layer of acid in a beaker, i put it outside and watch it. Nothing for 2 minutes, then the wind gave a gust or two, the acid had turned visabilly clear, after just a minute of wind it had turned clear. I reply cated this trick with more acid with a manual wind, me fanning the beaker with a big plank of wood. By this method the acid turned clear quite fast, i think the reduced pressure the air flow over the beaker is creating in the beaker, and the air flow carring any nox gases above the liquid away, thus preventing equalibrum of the liquid with the air is waht has caused this effect.


pete
Frequent Poster
Posts: 56
From: u.k
Registered: JAN 2001
posted 07-01-2001 07:35 AM
--------------------------------------------------------------------------------
One time i was left with some nitration acids, post nitration. I had read that nitric acid reacts with sulphur thus
S + 6HNO3 ----> H2SO4 + 6NO2 + 2H2O

This gave me an idea, what if you bubble the resultant NO2 gas through water to make nitric acid, you will have in effect then generated H2SO4 from water and sulphur. So i added a small amount of sulphur too my mixed acids, in a sealed flask with a pipe leading out of it to a boiling tube full of water. I heated the acids and soon a vigourious reaction was taking place, the water at first absorvbed the gas well, and but soon it turned red and absorbed much less well. Once the reaction had ceased i let the acids cool, i removed the sulphuric acid from the container, this was boiled till concentrated, and acted just like pure sulphuric acid. The nitric was of a lowish concentration, put was boiled to 70 % and again acted like good nitric acid. By the end of the reaction i had more conc sulphuric than i started with, and some 70% nitric acid. This reaction is, i'm told a modified version of the lead chamber process.



mongo blongo
Frequent Poster
Posts: 175
From: I live in a Creosote Bush!
Registered: JUN 2001
posted 07-01-2001 11:25 AM
--------------------------------------------------------------------------------
wow!! that is interesting!! im gona try these!!
nice one dude!!!


Anthony
Moderator
Posts: 2383
From: England
Registered: SEP 2000
posted 07-01-2001 06:11 PM
--------------------------------------------------------------------------------
The second idea is interesting... If the reaction was 100% efficient (so you always got as much HNO3 made as you used to release the NO2) then you could produce H2SO4 very cheaply. I wonder if there's a cheaper way to produce NO2? Heating NH4NO3 maybe?


zaibatsu
Frequent Poster
Posts: 412
From: England
Registered: SEP 2000
posted 07-01-2001 07:59 PM
--------------------------------------------------------------------------------
wouldn't you make N2O by heating AN?


Anthony
Moderator
Posts: 2383
From: England
Registered: SEP 2000
posted 07-01-2001 09:21 PM
--------------------------------------------------------------------------------
I thought it decomposed into both if over heated?


zaibatsu
Frequent Poster
Posts: 412
From: England
Registered: SEP 2000
posted 07-02-2001 01:03 AM
--------------------------------------------------------------------------------
I too thought it would, but asked mr Cool, and he gave this response:
Heating NH4NO3 ---> 2H2O + N2O (laughing gas)
Heating Pb(NO3)2 ---> PbO2 + 2NO2 (nitric oxide. Not as funny, but more
useful!)

So if you can find any lead nitrate you can use this, and so save on the cost of H2SO4, but I'm guessing it will cost more than it would to use H2SO4/KNO3



Mr Cool
Frequent Poster
Posts: 1013
From: None of your bloody business!
Registered: DEC 2000
posted 07-02-2001 03:05 PM
--------------------------------------------------------------------------------
I think it can make both if overheated in the presence of oxygen.
KNO3 can also decompose to release NO2, it's more common than Pb(NO3)2.


Anthony
Moderator
Posts: 2383
From: England
Registered: SEP 2000
posted 07-02-2001 04:24 PM
--------------------------------------------------------------------------------
Thanks for the clarification, possibly something worth experimenting with in the future


pete
Frequent Poster
Posts: 56
From: u.k
Registered: JAN 2001
posted 07-02-2001 04:24 PM
--------------------------------------------------------------------------------
After some more experimentation i have found that the reaction is an equalibrum, as all are, but pure nitric works best. I have come to the conclusion that the reaction is hard to drive, after much experimentation. Maybe someone else will have more luck, the reaction definately works however.

[Ollie Snowie]

You Have probably already thought of this but how about:-

PbO2 + 2NO2 --> Pb(NO3)2 + Heat
Then
Pb(NO3)2 + Heat --> PbO2 + 2NO2

You could absorb NO2 from a low conc. mixture (say from an electric arc), heat the lead nitrate formed and release fairly pure NO2. Use this to make some conc. HNO3 and re-use the PbO2. It has been said in "http://www.roguesci.org/theforum/showthread.php?s=&threadid=1919" that sillica gel will do the same thing. -Hope this is in the right thread as it's my 1st post.

[knowledgehungry]

I dont know what you are gaining from this reaction, why not just bubble the low conc NO2 through some H2O in the first place, reacting NO2 with PbO2 then reacting Pb(NO3)2 to make NO2 seems a little redundant, if you already have the NO2 i dont understand the point of making Lead nitrate just to make NO2 again. Maybe i am missing something.

[Mr Cool]

Yes, you are ;).

When making HNO3 with H2O and NO2, an equilibrium is reached between NO2 in the gas above the water, and NO2 in the water. We need as much as possible in the water. With air containing a low conc of NO2, such as that from an arc, there isn't much NO2 available to dissolve in the water, and an equilibrium is reached where the conc of NO2 in the water is very low.
However, with high conc NO2 in the air, or pure NO2, there is much more available, and so the high conc in the air will allow a much greater amount to dissolve in the water before an equilibrium is reached.
And so by forming a nitrate, and then decomposing it to form pure NO2, we can get much stronger acid.
A similar plan was mentioned in the thread in this section, about using an arc...
I hope that's clear, my thoughts aren't very lucid today due to a big fucker of a hangover, so I may not have explained myself very well...

[Ollie Snowie]

Just another thought on this:-
If NO2 is not very soluble in water and you have cheap, easy H2SO4, Why not make a nitrate from an oxide or hydroxide and NO2, then distill HNO3 from that and H2SO4. I have heard that some sulphates (such as CuSO4) decompose on heating to form an oxide and SO3, so that means that you could regenerate your H2SO4, make more nitrate and redistill.-- A bit of a long way round but with vacuum distillation you could get some conc. nitric acid.
Just another thought:-
If all you are after is H2SO4, you could re-use the nitric acid instead, or if you want both, you can keep adding S, O, and N at the required stages and tap the excess H2SO4 and HNO3 off as required. Presto! A mini nitrating acid factory in your shed.

[Ollie Snowie]

I recently read about this reaction (Thermal decomp. of lead nitrate). It doesn't do what I thought it would. It forms oxygen aswell as NO2, and PbO, rather than PbO2. The question is, could 3 NO2s oxidise it back to Pb(NO3)2, one of them being converted to NO?

What about something more reactive, for example, iron nitrate. Being more reactive, it might be better at holding its extra oxygen, and staying in its high state of oxidation.

Hey. I think I could have hit gold here. What about making iron nitrate from moist iron oxide/hydroxide and NOX (from an arc). Then React it with conc. H2SO4 and vacuum distill it, to extract the HNO3. Then (I hope i'm right on this bit) regenerate the H2SO4 by thermal decomposition (make Ye Olde Oil Of Vitriol) and also get back the iron oxide. I did try the last bit with some iron(II) sulphate from a chemistry set and it does need a very high temperature to completely decompose. But... As always... Electricity is cheap :)

[THe_rEaL_dEaL]

This copper sulfate --> Cu0 + S0₄

If this is right then this has much promise> A VERY cheap source of sulfur trioxide for H₂SO₄ production as where I live Copper sulfate is very available at even some well stocked supermarkets :) its crazy.

Could this Ionic sulfate principal work with a group 2 metal ion like MgS0₄ instead of a transition metal sulfate, as MgS0₄ is even more accessible in the form of epsom salts. Allthough it a crystalisation of water compound in packet form, from my short chem experience, an oven could fix that!

[simply RED]

This is wrong...

[zeocrash]

as far as i know, strongly heating copper sulphate does not form CuO or SO3, it instead forms a white powder known as anhydrous copper sulphate. the only use i've found for this is novelty in that when you add water it turns blue again and gets increadibly hot.

[Ollie Snowie]

simply RED-Which post are you referring to?
and
THe_rEaL_dEaL-We are not really bothered about making H2SO4 here. The H2SO4 is only used to displace the -NO3 from the iron nitrate. I was talking about how to recycle the -SO4 and -Fe so you don't have to keep adding H2SO4 and Fe2O3.
and
zeocrash-Heating hydrated copper sulphate to a bit above 100 deg. C just makes is anhydrous. Heating it more strongly makes it form CuO and something else (choking gas). I'm not sure about SO3 though. My instinct tells me it would be SO2 and O2 but I'm probably wrong. Anyway, it wouldn't matter if we were making HNO3 by the method described in my last post, because we could use excess iron nitrate to sulphuric acid, and then the heat would make it give off NOX as well as SO3, SO2 and O2. Any SO3 would react with the water in the reciever to make H2SO4 and then the NOX would catalyse the oxidation of remaining SO2. Then the waste gasses from this stage would be returned to the absorbtion chamber where it forms iron nitrate again with the moist iron oxide.

[zeocrash]

copper sulphate does not decompose to sulphur thrioxide upon heating.
when heated above 560°C it turns to anhydrous copper sulphate.
Properties: Grayish-white to greenish-white rhombic crystals or amorphous powder. On heating dec above 560degrees. d 3.6 . Hygroscopic. Sol in water. Practically insol in alcohol. Keep tightly closed. -the merck index
are you sure it's copper sulphate you're heating, i know copper carbonate breaks down to from CuO and CO2
edit: apoligogies, i stand corrected, i was just unable to find any reference to this anywhere i looked. merck index, reinhold chemical dictionary

[simply RED]

The post about decomposition of CuSO4 i was refering to.
It will decompose to SO2, O2 and CuO after the chrystalization water is removed. The decomposition starts when anhydridous CuSO4 is heated to 600 C.

[Jackotrades]

I'm a bit weak in the chemestry department. Couldn't strontium nitrate be decomposed to for NO2? If so, there's a big market for it...AKA road flairs.

[blindreeper]

Most things in chemistry look like they would work. A common question that came up when my class were doing ions and bonding is why don't you get O2 + O2 -> O4? It's the just the way electrons are. Some things look like they would work but don't, so in short, no