Sciencemadness Discussion Board

Potential source of sulfuric acid?

UnintentionalChaos - 19-12-2006 at 16:11

I have a very hard time procuring chemicals currently. A major one that I would very much like to have is sulfuric acid. I've checked all hardware stores and no cleaners they sell contain it. In fact, as of now I cant even find hydrochloric/muriatic acid, at least in a form without thickeners and scents. I did come across something interesting, however. They were selling containers of sulfamic acid crystals as a substitute for muriatic. After a quick internet search, I read that a solution of sulfamic acid will release ammonia with heating.

H3NSO3 + H2O -(heating)-> NH3 + H2SO4

Would this be a plausible reaction to carry out, or would SO3 be released as a gas as well? Would ammonium sulfate end up as a contaminant in the final product do to reabsorption of some of the ammonia? Could methods be employed to minimize contamination of the resulting product, or would they also minimize the amout of resulting sulfuric acid?

Baphomet - 19-12-2006 at 17:15

They're thickening HCl now? The end is nigh! :o

If the reaction proceeds the way you described (most likely using a catalyst) the ammonia would recombine to form ammonium sulfate as you suspect.

The good news is that two moles of NH3 are required to neutralise one mole of H2SO4 (unless a bisulphate is formed??) so you should have plenty of H2SO4 left over.

You might want to study which reaction conditions promote formation of NH4NSO4 and avoid if possible.

UnintentionalChaos - 19-12-2006 at 18:01

I will look into catalyzing that reaction, but I suspect that it may proceed without one (heating the sulfamic acid solution should liberate ammonia, at least according to wikipedia) I imagine that keeping the batch small and keeping it widely distributed in the heating vessel with good ventilation would minimize reabsorption of ammonia. Still I am worried that the formation of H2SO4 here is not almost instantaneous:
H3NSO3 + H2O -(heating)-> NH3 + SO3 + H2O -> NH3 + H2SO4

The heat released by the formation of the sulfuric acid may be a serious issue by vaporizing a lot of the SO3 before it can react with water, creating one hell of a dangerous cloud above the reaction vessel.

Bisulfate does form:
NH3 + SO3 + H2O -> (NH4)HSO4 (I assume this is more stable than sulfamic acid? Otherwise the sulfamic acid would just be regenerated in solution (in a closed vessel, which would have to withstand a huge amount of pressure and extreme temperatures).

This is looking like it may be much harder to generate a useable product than I figured it would be. Anyone have any suggestions?

woelen - 20-12-2006 at 00:43

Quote:
They're thickening HCl now?

They are doing things with HCl to make it less suitable for other uses than what it is intended for (cleaning concrete and brick walls).

Over here in the Netherlands we could buy 10% HCl of remarkable purity (really colorless and on evaporation no residue was left), we can also buy 30% HCl, but that leaves a residue on evaporation. I liked the 10% stuff, because of its great purity, which is particularly important for the kind of experiments I do with inorganic transition metal chemistry.

But since a few months, the 10% acid is bright yellow/green, almost like a solution of fluorescein. It is totally useless for inorganic chemistry experiments, due to the bright yellow color :(. Of course I could distill the acid, but it is really sad that such a simple product needs such treatment. And the bad thing is, it is not just a single brand, which has changed. All bottles of 10% acid at all shops now contain the yellow stuff :(.
The 30% material luckily still is colorless, but it leaves some residue on evaporation (probably some calcium and/or magnesium salts).

I don't know why the yellow material is added, but one of the members on a dutch chemistry forum said it is added in order to make things more difficult for meth-cooks. I myself think it is just to make it more fool-proof. The colorless material may be viewed as water and one could accidentally drink some of it. The bright yellow/green stuff definitely does not look like something you want to drink. The 30% acid apparently does not need such treatment. It fumes and makes the beaker in which it is look frosty, also something you definitely do not want to drink if you see it.

[Edited on 20-12-06 by woelen]

yellow HCl

imandroid - 20-12-2006 at 05:08

..I agree with your theory that it may be something other than a deterrent for use in meth manufacturing (maybe not so kids won't mistake it for something to drink since lemon fruit drinks come in the same poly gallon jugs along with fruit drinks from the grocery store and kids'll grab yellow over clear every time)..
Hcl went yellow here in the states a year or so ago which threw me for a loop beings I'm learned of the old school warning that yellow muriatic acid means it's gone south on ya, but this yellow HCl is no different from when it was clear as far as chemistry usage.. trust me on that..cuz think about it..have I ever lied to you since you've known me?
...that's what I thought.. :P
..don't use brick cleaning muriatic acid cuz QA isn't even needed with that application...rather use swimming pool muriatic acid.. anything used where kids'll be splashing around in is gonna get some special attention to be of purer quality than something scrubbin' oil blackened driveways and creosote stained bricks.. just my opinion of course....I'm well beyond lazy for researching while in the middle of a reply plus my feelings never get hurt from being corrected..that's some free slices of education for me without ever opening a search engine..lol... ;)

not_important - 21-12-2006 at 08:40

Ammonium sulfate, (NH4)2SO4, also loses ammonia when solutions of it are boiled; the acid- or bi- sulfate is the result.

If you were to pass a current of filtered (no dust) air through the mix while boiling, that might help sweep away ammonia. But I suspect you will end up with a mixture of sulfuric acid and NH4HSO4.

I've always distilled tech (brick cleaning) hydrchloric acid, to get rid of the iron salts in it. HCl gas comes over first, you can absorb that in water, previously distilled hydrochloric acid to get the ~ 35% fuming grade, or pull it through concentrated H2SO4 to get dry HCl, condense with dry ice and store under pressure. When the concentration gets down to constant boiling ( 6 M, 20.2 % BP 108.6) just distill most of what remains over. Or you can add enough water to give a starting acid of about 6 M and distill that. It fumes a lot les, so is easier to store.

Baphomet - 22-12-2006 at 02:38

Just a thought, but since HCl is such a pain in the arse to distill what about just dumping a whole lot of NaCl into it? Then the gas can be vented off and dissolved in the normal way