Neutralising sour AP?

[Potassiumchlorate]

I have some ammonium perchlorate that I bought for a pretty fair price. Unfortunately the dealer had moistened it with water, so I heated it in the oven before trying to mill it. Despite the relatively low temperature it started decomposing. Now it's a bit yellowish in colour, smells of chlorine and has a pH of about 2. I found out that small amounts could get an almost neutral pH by milling it for a short time and drying it outdoors in the sun, but is it pure enough? I have understood that ammonium perchlorate is always a bit acidic and that it can be yellow even if you haven't made an attempt to dry it and out of mistake started decomposition.

 

Any AP experts on the subject?

[Potassiumchlorate]

Anyone? After several hours outside (still without milling) the acidic reaction is almost gone.

[FlaMtnBkr]

I don't have any info for you. Heck, I didn't even know AP had a tendency to sour and I have read plenty about it. What I'm curious about, is why in the world would the chem dealer wet the AP?

[Potassiumchlorate]

I don't have any info for you. Heck, I didn't even know AP had a tendency to sour and I have read plenty about it. What I'm curious about, is why in the world would the chem dealer wet the AP?

 

Oh, it seems that he was a bit concerned that the AP would be unstable if completely dry.

[pdfbq]

Ok, here my 5 cents for what its worth.

 

I made all together about 1.5 kilo of AP and was experimenting with production methods so i read a little about it.

 

I think in industry AP is made by first making perchloric acid from NaClO4 and HCl and then adding ammonia.

I tried the same but the problem here is that you need very concentrated HCl and even then a lot of HCl is not converted to HClO4 because when the HCl concentration is getting to low it does not displace anymore with the NaClO4.

So to make good HClO4 you have to boil off the left over HCl, get rid of the precipitated NaClO4 and NaCl, and do the same trick another two times or so.

 

I can imagine that your batch contained some of this left over HCl.

 

The way I make AP now is by adding an ammonium nitrate solution to my NaClO4 solution (NO NaClO3 SHOULD BE PRESENT BTW!!)

This will give me a yield of about 50%. The other 50% I harvest by adding KCl which gives me perc.

The AP I get by this method is white and does not smell chlorine.

[Potassiumchlorate]

Hm, thank you, but I think the HCl here was formed by decomposition of the AP. I had a temperature of 200^oC in the oven. I had read that even low quality AP wouldn't decompose below 260^oC, but it seems this was wrong. That was stated by Takeo Shimizu himself. In Wiki I read that it might decompose already at 210^oC, though.

 

I wonder if I could simply rinse it in anything that doesn't dissolve. Water won't do, of course and neither will ethanol.

[Potassiumchlorate]

Update: my AP is still a bit acidic but it's considerably less acidic than before the milling (I have a separate thread about some phenomena occurring when milling AP and copper(II)chloride). The weird thing is that in a concentrated solution it doesn't turn out to be acidic at all, but when putting an indicator paper in the dry powder, it becomes a little pink at the edges.

 

But isn't AP always a bit acidic? From what I've understood a salt doesn't necessarily have a pH of 7, no matter how pure it is.

[Mumbles]

This is actually something I've been wondering about since you posted this yesterday. Ammonium perchlorate is supposed to be acidic, at least the solutions are. Just dipping wet indicating paper into dry will quickly make a weak solution on the surface of the paper and may or may not get all that concentrated to register much of a change. Not all salts will make neutral solutions. That said a pH of 2.0 is way too low. You'd expect something in the range of 4.5 and 6 or so.

[Potassiumchlorate]

This is actually something I've been wondering about since you posted this yesterday. Ammonium perchlorate is supposed to be acidic, at least the solutions are. Just dipping wet indicating paper into dry will quickly make a weak solution on the surface of the paper and may or may not get all that concentrated to register much of a change. Not all salts will make neutral solutions. That said a pH of 2.0 is way too low. You'd expect something in the range of 4.5 and 6 or so.

 

Well, that's interesting. When I mix it with hexamine (dry), I feel a distinct smell of ammonia, not much, but I can feel it. That pink colour at the edges means that it is at least close to 2.0 on that precise spot, but most of the paper is still yellow, i.e. pH 4.0 to 5.0. If Wikipedia is correct about the properties of hexamine, it starts to decompose into ammonia and formaldehyde below pH 5.5. That means that my AP at least has a lower pH than 5.5.

[pyrojig]

Here is an idea.

I always try to recrystallize my salts to obtain max purity when needed. Here is a link about ammonium salts and their solubility 's . Try to recrystallize your AP to get it clean and pure again.

 

http://www.chem.memphis.edu/bridson/FundChem/T17a1100.htm

[Potassiumchlorate]

Thank you for the link.

[pdfbq]

Recrystallizing AP will give relative big losses.

100 -> 0 C^o

57.01g -> 11.56g

Which means you loose at least 11.56 grams for every 57.01 gram you put in ~20% but i guess closer to 25% due to the washing.

 

There's one trick and that is make perc from the AP that is still in the left over liquid by adding KCl soln