charley1957
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Separation of two inorganic compounds
Dry chemical ABC fire extinguishers contain a mixture of two different chemicals: Monoammonium phosphate and Ammonium sulfate. I was given several
pounds of this powder, and wanted to see if I could separate them from each other. After I UTFSE for several hours and a couple of days of scouring
the internet and learning about various aspects of this problem, I find I'm at a standstill. Both compounds are soluble in water, and both are
insoluble in ethanol and acetone. I've not been able to find anything else about their solubilities. They are both acidic, one at pH 4.7 and the
other at 5.5. One is stable to 200 degrees C, the other to 250. I'm just trying to do something here I thought I could figure out, nothing other
than self-education. Any suggestions would be greatly appreciated.
You can’t claim you drank all day if you didn’t start early in the morning.
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Fulmen
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Have you tried dissolving larger amounts of this material? I have, and it was a mess. It's both fluidized and hydrophobic, you do the math...
Also, do you have the actual composition? Dry chemicals can be a mixture of a myriad of compounds. I don't mean to discourage you, just check before
you get all excited.
Personally I would precipitate both the phosphate and sulfate with calcium nitrate, producing a mixture of ammonium nitrate and nitric acid.
[Edited on 3-10-21 by Fulmen]
We're not banging rocks together here. We know how to put a man back together.
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unionised
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https://en.wikipedia.org/wiki/Solubility_table
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woelen
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I would keep the mix as is and use it for making NH3. Both chemicals can be used very nicely for making gaseous NH3, if you mix them with NaOH and
initiate the reaction with a drop of water.
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charley1957
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@ Fulmen No I’ve been doing just the homework before I tried anything else. I kind of suspect what you found to be true because of the nature of the
powder.
@ unionised What I meant by that statement was I wasn’t able to find out what other solvents the compounds were soluble in. I found all the water
solubility info. Thanks for the effort.
@ Woelen Actually that sounds like a good idea. I’ve not done anything with ammonia yet. This might be a good time to start.
Thanks all for all the helpful suggestions.
You can’t claim you drank all day if you didn’t start early in the morning.
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Tsjerk
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When you want to dissolve ammonia gas in water, make sure to cool the solution. The colder it is the more gas you can dissolve, and dissolving ammonia
in water is exothermic.
[Edited on 4-10-2021 by Tsjerk]
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teodor
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Also ammonia gas, surprisingly, doesn't dissolve well in water without mixing.
Check my pictures here: http://www.sciencemadness.org/talk/viewthread.php?tid=26378&... There is something like 5 to 10 mins between the first and the second picture. But
one shake is enough to mix it. So, shake the solution from time to time.
[Edited on 4-10-2021 by teodor]
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charley1957
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I tried to dissolve some of this powder, and it was just as Fulmen described. Very hydrophobic, even with heating and extreme stirring over long
periods of time. I was able to get some to settle to the bottom of water, but just a little disturbance and it would come back up. No, I haven't
been able to find out the actual composition. Seems these two chemicals are usually in a 60-40 mix, and interchangeable at that. I'm unaware of how
chemical fire extinguishing works, so I guess there's a reason for their interchangeability. I'll play with these some more.
You can’t claim you drank all day if you didn’t start early in the morning.
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Jimmymajesty
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It is hydrophobic due to the presence of silicon oil, google abc powder msds, there is also silica and talc, maybe calcining it then leaching will get
you some H3PO4 or the slag after milling with Al and some more SiO2 would be good to make P?
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MadHatter
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MSDS
I can't claim this MSDS for ABC extinguisher as "1 size fits all" but here it is for
what it's worth:
Attachment: FIRE-EXTINGUISHER-ABC.pdf (90kB)
This file has been downloaded 184 times
From opening of NCIS New Orleans - It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !
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Amos
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I'd try to degrease the powder well with a cheap solvent, like acetone. You don't have to get all of it, just enough so that the solids will dissolve
in boiling water given enough time. The remaining oil or insolubles could be filtered out or decanted off.
Personally apart from wanting to use the entire refined mixture for ammonia generation as has been mentioned already, I wouldn't attempt to separate
these from each other. What I would do instead, in order to get ammonium sulfate out of it, is buffer the solution with a little aqueous ammonia and
then add magnesium sulfate(epsom salt) solution until no more precipitation occurred. This would, correctly done, leave you with a solution of only
ammonium sulfate and a lot of magnesium phosphate precipitate; this could potentially be used for phosphoric acid, construction/ceramic materials, or
even elemental phosphorus if you're clever enough. Or you could just toss it; You've already scavenged all of the ammonium ions and epsom salts are
dirt cheap.
Ignoring hydrates, which you'll have to input manually into your stoichiometry:
2 NH4H2PO4 + MgSO4 = (NH4)2SO4 + Mg(H2PO4)2
Magnesium dihydrogen phosphate disproportionates, generating phosphoric acid and magnesium hydrogen phosphate:
Mg(H2PO4)2 = MgHPO4 + H3PO4
With added ammonia, the phosphoric acid is neutralized and continues to be precipitated out irreversibly as magnesium hydrogen phosphate. This is just
a pretty specific example of something you can do with the product; with luck you'll get a whole selection of good suggestions that yield different
compounds.
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Fantasma4500
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so... triammonium phosphate is about 7g/100mL 0*C (insoluble in acetone, probably likewise for EtOH)
ammonium sulfate is about 70 at that (insoluble in EtOH)
monoammonium phosphate is about 25 (insoluble in EtOH)
i messed about with ammonium phosphate a lot but now i cant remember if you just douse the mono version in ammonia to get triammonium phosphate?
its super B fertilizer.
i cant remember which form these crystals were made with, very difficult to make proper crystals, seems nearly impossible to just continously grow one
single crystal, this crystal crop was more luck than anything.
https://gyazo.com/147721c059ecbe059576b23a5c306964
i would go with converting the monoammonium phosphate into triammonium phosphate, then crashing that out of solution, and doing whatever with the now
impure ammonium sulfate
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