NH3 gas

[frogfot]

What apparatus would be best to produce NH3 gas from NaOH and NH4Cl (or NH4NO3)?

Asking this because i got some problems. Synth of acetamide required that you pass ammonia gas through liquid (no need to dry the gas) As gasgenerator I used a filtering flask with a corc (a syrigne with water was placed through the corc). A mix of mentioned salts was placed in flask and pipe was immerced into solution.. Flask was in cold water-bath At first reaction went fine and steady without water, then, when it slowed down i started to add some drops of water. This resulted in vigorous evolution of gas which stopped quite fast. Further addition of water resulted in underpressure in flask.. as result some liquid from my acetamide experiment was sucked into flask.. :(

How to prevent this? I don't wanna place any safety vessel between gas generator and experiment vessel cause this would be only temporary solution... Maby there are some standard equipement one have to use?
Thanx for inputs

[yt2095]

in your ammonia receptical, make it a shallow dish (a few mm deep only)
then on your gas pipe attatch a funnel and put that into your dish. since ammonia is so readily absorbed in water other liquids a vucume is often produced, but now when it does, it will TRY suck up your liquid, get so far up the funnel and drain yor dish untill air comes in and releases it :)
it also has the advantage of giving your ammonia gas a greater surface area in which to react with your liquid :)

all the best :)

[frogfot]

yt2095, you're genious! This is a great idea, thanx :D
Now, wonder how one could maintain steady gas production.. i'll test this again with more finely devided particles, maby water produced in reaction will keep reaction going all the way.

[FragmentedSanity]

Lo all :)
check the hive - or rhoidiums site might be quicker. Ive seen a couple of ammonia gas generators. The ones i remember seeing are for making anhydrous NH3 gas - to be condensed into liquid NH3 for use in birch style reductions. Seeing as this process requires LOTS of gas (fairly constantly) the generators described may be quite useful.
FS

[John Ashcroft]

What reaction are you using to prepare acetamide? Are you going to be bubbling ammonia into ethyl acetate (nail polish remover)? Acetamide *can* be more easily prepared by simply heating ammonium acetate, distilling off H2O, and then acetamide (separating fractions, of course).

[frogfot]

John, yes, preparation method requires bubbling of ammonia gas (through a mixture of 20 g ethyl acetate and 30 g 25% ammonia)
I'm really grateful for suggestion, i'll try both methods. It's not the final product thats my goal (though it is also..) :)

Searching for rhodium site i found this:
www.rhodium.ws/chemistry/birch.mrclean.html

NH3 is prepared by mixing powders of NaOH and ammonia salt. Testing this i found that one have to sit by apparatus and shake the vessel every 2 minutes.. too much work.. then I ran out of NH4Cl had only ~20g no wonder it wasnt enough (gonna make half kg today)

Then again some wisdom came from old books, they drop conc. KOH solution onto solid NH4Cl and dry gas with KOH (not nescessary in my case), now this seems to be comfortable method. It would be quite logical to think that solubility of NH3 in conc. basic solutions falls drastically, therefore, maby NaOH will do just as fine.

[IPN]

If you don't have much ammonium chloride you could use urea instead, I think it would be cheaper than ammonium chloride as urea is easily acquired as a fertilizer.:)

The reaction is as follows:

2 NaOH + CO(NH2)2 --> Na2CO3 + 2 NH2

You may need to heat the mixture a little to get things going.

[Mumble]

If you had the neccesary heating apparatus around, you could just heat the urea to decmpose it into Ammonia and cyanic acid. Even though you don't need it to be, it is dry. The only water present would be that which is in the air. If this is possible for you, I don't really see why not use it. Urea is more economical to use than an ammonium salt and NaOH, for me at least.

[mongo blongo]

IIRC you can prepare dry NH3 from Ammonium Sulphate (from a garden centre) by heating.

[Mr Cool]

True, and the NH4HSO4 left behind can be used, after converting it to the sodium or potassium salt, to make SO3. Search and ye shall find...

Although heating ammonium sulphate does produce dry ammonia, which is nice, I've always preferred using NH4X + NaOH. I don't like having to heat my glassware up that much, because I always end up breaking it with thermal shock :(.

[frogfot]

Wait, wouldn't ammonium sulfate give off both NH3 and SOx? If not, this would be a good mass production process for some people. It have decomp. temp. at 280*C, so thats ok for an amateur experimenter. No complicated equipement is needed, just a big iron good sealed jar on a fire place :)

Btw, gardening stores here sell for the most only mixed fertilisers/other chems.

[Mumble]

The way people were talking, It appeared that the Ammonium Sulfate just gives off one molecule of Ammonia gas, leaving Ammonium Bisulfate. I believe the decomposition of Ammonium bisulfate will give off the SOx. I'd imagine the decomposition temperature of Ammonium bisulfate is higher than that of Ammonium Sulfate. If it wasn't, the Ammonium bisulfate would be decomposed as soon as formed. Thus producing a contaminated product.

Just bubble some of the gas into water. Then evaporate the water. If theres any SOx there will be crystaline solid at the bottom. You could also bubble it throught a saturated solution of CaCl₂, any SOx will be removed by the formation of Calcium Sulfate. Don't use the gas you bubble through. It will be contaminated by HCl.

[frogfot]

Found a pic in nonorganic book of an apparatus that suppose to produce continiously gaseous ammonia, heres a it:
http://www.geocities.com/frogfot/stuff/ammoniaapp2.gif (Copy&Paste)

This vessel is welded from a peace of iron pipe (11 cm heigh and 9 cm in diameter). Vessel is filled to half with water and heated to 98*C, after, aqueous ammonia is added with required speed to maintain wanted NH3 flow. Liquid is drained from vessel through pipe 1 (on pic). Evolved NH3 is dryed by KOH.
If properly regulated, author claims, this apparatus may operate in several hours leaving behind <2% aqueous ammonia.

Couple minutes of thinking gave me this simple to make apparatus that operates similarly:
http://www.geocities.com/frogfot/stuff/ammoniaapp.png (Copy&Paste)

Here, it is simpler to monitor liquid level inside flask.

Ofcaurse, one can use plain flask with one output if one needs only small ammounts of NH3.

I havn't tryed this yet, any suggestions?

Btw, 24,5% ammonia is very common in this country, lucky me :rolleyes: