Sciencemadness Discussion Board

Thermal reactions of dry ammonia!

Friedrich Wöhler - 13-2-2004 at 06:21

I'd wish, we collect in this thread all known reactions of ammonia-gas in higher temperature (or in liqid ammonina too).
I think about its special character as a better reductor than atomic H2 and a better "amidizer" or "imidizer" or "nitridizer" than atomic N2 or mixtures from N2 and H2.
Maybe you all know, using NH3 make it much easier bulding metal nitrides than atomic N2. I think even about it could be possible getting alcali metals (it means self-decomposible alcali-amides, -imides, -nitrides) from heating their salts with passing ammonia (exchange the old anion with *NH2 or *NH or*N), while the old anion will build its ammonium salt.
I burn of expectation about an equation like this:

Na2F2 + 4 NH3 ====(heat)====> (NH4)2F2 + 2 NaNH2
By the way...Na-amide decomposes in vacua over 200°C to Na-imide at first, then to Na-nitride and at least to Na.

You see, all my thinking bases on the possibility, ammonia-molecule breakes in a kationic and an anionic part:
[ 2 NH3 <====(heated or liquid)====> NH4-kation + NHH-anion ]

Highest interesting are also reactions like this:
2 NH3 + C =====> NH4CN + H2 (ammonia passing glowing coal)


So I think about getting a lot of ammonia by cheaply mass-chemicals:

You need:
- an ammonium-salt-fertilizer [ NH4NO3 or (NH4)2SO4 ]
- calcium oxide or -hydroxide
- an empty gas-flask (propan-flask or so...)
- maybe a pressure-sprayer from plastic (for the garden, its not expensivly)
- a compressor with ca. 20 bar pressure (maybe from a secon-hand-air conditioner of untill 2kW power)
- a refrigerator (deep-freeze)
- connecting materials like metal-pipes, manometers and so on...

For amateur's conditions I think, process must be splitted in two ore more parts.

Prepare a vessel for building ammonia and give a good homogene mix of NH4-salt and CaO inside. (little bit more CaO than the equation says).
Let the gas pass a water-cooled vessel to condense a part of that unwanted water as a concentrated NH3-solution.
Let cooled gas press by the compressor.
Behind compressor cool it down, maybe in self-made colling-spiral from copper pipe or so, in ice-water. Under this conditions pressure must fall down on 6-8 bar maybe and the ammonia becomes liquid. Let it inside that pressure-protected vessel. (big plant-prayers available untill pressure 12 bar, I believe)
Now you have liquid ammonia, contaminated with a bit of water and compressor-oil!

Purify it later:
Make a good cooling for a gas-flak of metal (empty propan-flask...) and connect it with that vessel using metal-pipe and a dryer with loosely CaO or alcali hydroxide in the middle of it. (You cannot use CaCl2 because of bulding an ammoniakat: CaCl2-6NH3 !)
Warm the primar vessel on a mild temp like 50°C or so and let the gas pass the dryer slowly. Let it re-condense into the cooled gas-flask. (Instead of colling the gas-flask you can cool the pipe of cause...)

Now you must have an oil-free and highly water-free liquid ammonia.

(I hope, that all is enough specialized to open a new thread...)


Organikum - 13-2-2004 at 10:53

ehem, bad idea. No copper together with ammonia as the copper gets rapidly attacked - by wet ammonia even more as by dry ammonia.

Plain iron is the cheapest solurion here and works well.

The design is overkill. The compressor is not needed at all so you can get your hands on dry ice what is possible alsmost everywhere.

Reactor - precooler with icewater - drying tower with NaOH/CaO - condensor with CO2 (dryice)/IPA mixture - storage pressure vessel which is also cooled by dryice/IPA.

Friedrich Wöhler - 13-2-2004 at 11:16


ehem, bad idea. No copper together with ammonia as the copper gets rapidly attacked - by wet ammonia even more as by dry ammonia.

No no no!
Copper works as catalyst oxidizing ammonia, building ammonium nitrite.
Please show me, where in this process is the oxygen to oxidize ammonia? :P :P :P

dry ice

Ohhh I forgot! We all here get nothing easier than frozen carbon dioxide... :D :D :D

Just tomorrow morning I will buy a lot of it in the next bakery! :P

Friedrich Wöhler - 13-2-2004 at 11:29

Oh now I understand...!
Alpine Austrians maybe don't know our problems how to find a source of that,
I'm not sure, but can it be, that white powder on top of the Großglockner* is frozen CO2 ?? :o :o :D

(*Grossglockner = Austrian's highest point)

Greetings for the Mozartkugel of us! :)

Aber Herr Wöhler!

Organikum - 13-2-2004 at 12:53

Ich darf doch bitten!

I am not talking out of my eh - left elbow - here. Please check the compatibility of copper/ammonia by yourself, would you?

No brass, no copper with ammonia! Period.

Already posted in another thread:
"Trockeneis fuer jedermann"
with link.
Germany, 24h to 3 days.
Or: put a bottle CO2 upright down and open the valve! Snow! Solid CO2!
As every welding shop and every inn uses CO2 this shouldnt be so hard to get.
In the worsr case: You can do the same trick with a propane bottle. Dangerous but works.

Ach ja, ich bin kein Oesterreicher. k.u.k. Oesterreich war etwas groesser....

NO From NH3

hodges - 13-2-2004 at 16:29

Paste this link into a browser and look at Experiment 8. It describes how to make NO from NH3 and O2 in the classroom.

Hodges, it's nice use the URL tags to make links clickable.

[Edited on 2-14-2004 by Polverone]

BromicAcid - 13-2-2004 at 21:39

After only minor google searching it is evident that Ammonia has not been used with copper in the cooling industry, the only incidence I found of it being used was a case report of a catastrophic failure that occurred within 2 hours of operation due to its use! Ammonia will also attack monel metal which has a high percentage of copper. Even anhydrous ammonia will attack copper and it is catalyzed by any copper oxide present, even a copper pipe exposed to the atmosphere for minimal time will have enough oxide present to catalyze the reaction.

don't ruin this thread

Polverone - 13-2-2004 at 21:43

It started out interesting and now gets sidetracked with insults.

Friedrich Wöhler: You were initially talking about making ammonia gas, then mostly-drying it and cooling it in a copper tube. Organikum said to use iron, as copper will be attacked by ammonia. This subsequently degenerated into an argument about how/why/when ammonia will attack copper.

But it is very clear how ammonia will attack copper in your original idea: copper oxidizes in air, tarnishing, and when ammonia is available in the presence of water, the oxidation products are immediately dissolved by complexation, further exposing the metal to attack. You may well get copper contamination of the ammonia even if your copper tube was super-clean, and you will certainly get contamination if the inside of the pipe had already tarnished. How much this contamination matters will probably depend on the final application.

Organikum: I got an error trying to open that rar file.

BromicAcid: what is the mechanism of attack? I suppose the ammonia itself must serve as the oxidizing agent?

[Edited on 2-14-2004 by Polverone]

Friedrich Wöhler - 14-2-2004 at 10:51

Well, I'm not a hot head, but I have a lot of hate against that erected finger like in a photo of Bin Laden and my blood will boil, when anyone brakes into thread like an elephant into a procellain store, say "Yor are completely false" without giving a reason and goes out so quickly as he came in. Another one who did so, admitted his mistake nevertheless humorously. But strict human vanity is poison for every kind of internet forum. When I feel I must speak out my doubt now, I do that gently. In such case, its usual to say "Are you sure?" and to justify doubt. I don't let anyone speak at me, so as I had not a little bit of knowledge. Since 100 Years I know that kind of oxidation of ammonia by molecular oxygene, catalysed by copper over intermediately build copper oxide. I even experimented it !! And have seen that characteristic dark blue solution of that tetrammine-copper(II)-hydroxide in front of my own eyes! I did read in books enough and know this process bulding ammonium nitrite. Even I was thinking about producing this Cu(OH)2-4NH3 [or other ammoniakates like CaCL2-xNH3 (x=number)] for getting pure, dry ammonia as a chance to separtate NH3 from moisture comletely and easily. Cause for this consideration where the technical difficulties under amateur-conditions in a small apartment maybe (!) for producing, drying, purifying and condensing by pressure or deep cooling or both, all together. Therefore I suggested compromises at the moment. At first, a cheaply compressor from an old air conditioner will easily and cheaply to get, its also silent enough for an apartment in a city as an example. Naturally will that non-purified ammonia contain a little bit of NH4NO2 and Cu(OH)2-4NH3, so as it will contain also moisture and compressor-oil, I wrote. In my suggestion to split the process in two steps, that all will be completely indifferently. In the second step you will work without any water-building and without any machines and you can adjust the stream of ammonia as you want - but what you can not, if ammonia must been cleaned, dryed and condensed all at the moment in that speed in which its chemical pruduced. In this slowly evaporation in second step you can realize fine adjusting from that intermediately vessel (go in bed and let it run over night) you are not more dependently of speed of chemical ammonia bulding (what's never easlily to adjust). By the way, its also not easily as an amateur to build an enough pressure-protected reactor and following condensing- and drying-equipment. A compressor can take too high pressure off from the side, where ammonia develops continously.
Furthermore a comressor will anyway be needed for so many other experiments, like make a vacua as an example.
Years along I have good old printed chemistry books eaten, sitted weekends along in university library, reading about nitrogene and ammonia chemistry from ground to top and backwards again. I never found one fucking sentence, ammonia and water could oxidize copper, without oxygen, without metal-oxide or any O-compound at normal temperature. Naturally copper will decompose gaseose ammonia and get nitridized in glow-tempetarture. But not under these conditions here. I have books really eaten! And found no one sentence about possibility of such reaction. Since half of my life I am an intensivly book-eater! If then comes anyone to me and says I should search google, (so as I had asked, how to make nitric acid from sulfur and water or what the difference between element and compound is) my head will fall down on table.
Furthermore I've seen old refrigeratores (from age before using organic halides) with copper pipes. If pure copper could reduce water in present of ammonia without only one fucking O-atom, there would build a lot of uncompressable hydrogen gas, making this plant uselessly, because of pressure-conditions in it are fine adjusted.

So after this intermediate pretty play of human problems, thread will return to chemistry.

At jokes about Austrians can him really not concern, because of he isn't an Austrian, I just know, he is a Czech one.

[Edited on 14-2-2004 by Friedrich Wöhler]

no more of this

Polverone - 14-2-2004 at 11:28

The first insulting post I see in this thread is the one "OK OK the earth is a disk!" Any further discussion in this thread will be completely about technical/scientific matters.


Mephisto - 14-2-2004 at 11:29

Copper dissolves not only in oxidizing acids but also, for example, in ammonia or cyanide solutions in the presence of oxygen because stable complexes are formed. Also acetic acid together with oxygen or hydrogen peroxide attacks copper forming a green pigment called verdigris.


another interesting reaction

Polverone - 14-2-2004 at 11:44

At elevated temperatures, zinc reacts with NH3 to form zinc amide. Is this amide of any use, perhaps like its alkali metal counterparts?

Friedrich Wöhler - 14-2-2004 at 13:23

Copper dissolves not only in oxidizing acids but also, for example, in ammonia or cyanide solutions in the presence of oxygen because stable complexes are formed. Also acetic acid together with oxygen or hydrogen peroxide attacks copper forming a green pigment called verdigris.

My speech.

In my technical suggestions I always assume from social conditions in Western Europe where we live like oil-sardines in a can. Can be, someone living in USA or Canada, could cheaply buy or rent a primitive land house, where he can construct big apparatures, make some noise and so on, will say "Why should I split the process?" On photos, linked from forum I've seen chemical equipments and constructions and sulfuric acid in a plastic bag in bedroom between bed and curtains.
Caused by such conditions I also never stop thinking about such as absorbing roughly ammonia gas in water, building complexes like CaCl2-xNH3, dry them at low temperature and then let them re-evaporate, only to avoid monstrouse and dangerously constructions in a small apartment or so.
Sometimes I think about my neighbours in the under floor, sitting in a soft couch, cooking a fine meal in their kitchen, while 2 meters over there head I abuse my kitchen, distilling a cubic meter of pure hydrogen fluoride... *lol*
I assume, dryed Ammin-salts could be used to dry damp ammonia similar as that perfect desiccator alcali-amides (water goes in, ammonia comes out). Anywhere I tried to let dry Cu(OH)2-4NH3 [ or Cu(NH4)4OH6 ] and hoped to get it crystalline, but it dried amorphe to an objekt like a rubber foil.

Now I have an idea, how could a construction look for experimantal building ammonium cyanide ba passing ammonia trough glowing coal.
Ammonia must be dry enough. Furthermore I think, professional activated coal will be much better than charcoal (also activated coal is not so expensivly.)
If you cannot work outdoor, a good heating could be a burner from an old *Gasdurchlauferhitzer* (I don't know, what's in English, it heats water so its runs), working with gas.Its burner has many nozzles on a large surface. Then there are oven-pipes (or rainwater-pipes) available with a small diameter, 10 cm in example. Put coal in it and fix it at both sides by iron-wool. outgoing side of pipe bend so, that you can cool it with water (maybe often you must knock that pipe-side that a lot of sumblimate cannot block cooling effect. Both ends of pipe close with a cover (weldering, soldering....?) and connect on these covers transmitting pipes for ingoing ammonia and outgoing hydrogene and cyanogene (poison!) Outgoing gas let go outdoor or oxidize it completaly in a flame.
Before reacting naturally you must make apparature air-free (using ammonia or nitrogene) and pre-glow the coal for escaping absorbed gases like CO2.
OK, but now comes my biggest problem: I still never found a note about needed temperature for decomposing ammonia by carbon. Also of this cause I recommend to use activated coal, it will lower the needed temperature, at it reaction takes place...

Friedrich Wöhler - 14-2-2004 at 13:54

Originally posted by Polverone
At elevated temperatures, zinc reacts with NH3 to form zinc amide. Is this amide of any use, perhaps like its alkali metal counterparts?


Can you find any notes about temerature?
zink and aluminium are the electropositivest metals we can easily get! I think, building of azides from their amides as an example cannot be so much differently from case of alcali metals. I could believe furthermore, that historical method getting cyanides (using elementary pottassium or sodium or there carbonates with reducing coal, using N-containig organic waste) can take place with zinc similar easily. Surely easier than to use carbonates and coal. You cause a new idea in my head: What will come out, melting cyanuric acid with zinc?? (cyanuric acid from decomposition of urea). Maybe I can construct a hypothetical formula, my head is still starting to smoke...

Friedrich Wöhler - 14-2-2004 at 14:28

I think, its not needed to post how to purify NH4NO3 as ammonia-source from this fertilizer:
80% NaNO3 + 20% CaCO3 and/or MgCO3 (I don't know its English trading name)
so I posted in a German forum detailed, it will be enaugh described here I believe, but I haven't desire to search now.
Has anybody need I will let it follow.

Theoretic - 15-2-2004 at 07:16

"NO From NH3

Paste this link into a browser and look at Experiment 8. It describes how to make NO from NH3 and O2 in the classroom."
Dazed but...
If it would be so easy to use COPPER instead of A PLATINUM-IRIDIUM ALLOY, it would of course be used! The catch, I think, is that copper is oxidized by ammonia/water vapour :).
BTW, ammonia reacts with white phosphorus at red heat to give N2 and PH3.

Clickable Links

hodges - 15-2-2004 at 09:18

Hodges, it's nice use the URL tags to make links clickable.

[Edited on 2-14-2004 by Polverone]

Okay, I wasn't sure about that. I have been on boards before where administrators do not want the board appearing in other sites logs (which it will as a "referring link" if a direct link is created). But if thats not a problem here I'll make the links clickable from now on.