Sciencemadness Discussion Board

phosphoric acid identification

justanamatuer - 31-10-2018 at 19:27

i'm not going to beat around the bush here so here goes. my mate has gone to jail for dealing meth. in my possession is a big container labeled phosphoric acid. thing is I remember him saying something about the wrong label on it & it being hypophos. how can I tell which one is which? its very heavy and is only half full. the liquid almost looks like runny oil and it smells quite sour.
is there a test I can do? or do the 2 look and smell different? thanks for any help

fusso - 1-11-2018 at 02:08

Hypophosphoric acid reduce Ni2+ to the metal but H3PO4 don't.

happyfooddance - 1-11-2018 at 07:20

Why, oh why, did anyone need to know about your friend going to jail? Do you think that has any relevance to the chemistry of phosphoric acid? Do you think people are more or less likely to help you knowing this useless tidbit?

hissingnoise - 1-11-2018 at 07:31

Quote: Originally posted by happyfooddance  
Why, oh why, did anyone need to know about your friend going to jail

What difference does it make to you, anyway ─ is the next question?


Jackson - 1-11-2018 at 08:04

If you have a distillation apparatus, maybe distill it and compare its BP to phosphoric and hypophosphoric acids to determine what it is.

fusso - 1-11-2018 at 10:01

Quote: Originally posted by Jackson  
If you have a distillation apparatus, maybe distill it and compare its BP to phosphoric and hypophosphoric acids to determine what it is.
hypophos decomp @130C but phos dec @158C. How could one determine whether the sample is decomposing?

Jackson - 1-11-2018 at 10:17

If it evolves a gas when decomposing than you could tell by the solution bubbling

Vomaturge - 1-11-2018 at 10:22

Quote: Originally posted by happyfooddance  
Why, oh why, did anyone need to know about your friend going to jail? Do you think that has any relevance to the chemistry of phosphoric acid? Do you think people are more or less likely to help you knowing this useless tidbit?


Because, if he hadn't included it, we'd be asking him why he had a chemical in a labeled bottle, but suspected it could be mislabeled. It sounds like his friend owned the chemicals before, and left it with him when he went to jail. He may have mislabeled it as "phosphoric acid", and it may have been hypophosphoric or even hypophosphorous.

Personally, I'd be reluctant to keep any chemical given to me by someone suspected of dealing drugs. Even if it is something legal, receiving it from your friend could make the authorities suspicious that you were involved with the drugs. Also, don't breathe or smell mineral acids (or any unidentified compound) if you can avoid it. Some are very harmful when inhaled.

As far as identifying it, maybe try a combination of titration and density measurements? Or, a melting/freezing point measurement?



[Edited on 1-11-2018 by Vomaturge]

Also, unionised idea below for testing for hypophosphorous acid looks like a great, straightforward one. Add it to copper sulfate, and you'll eventually get copper hydride.

Of course, if what you have is actually hypophosphorous acid, then you are probably (depending on where you live) breaking the law just by owning it!

[Edited on 1-11-2018 by Vomaturge]

happyfooddance - 1-11-2018 at 11:26

Quote: Originally posted by hissingnoise  
Quote: Originally posted by happyfooddance  
Why, oh why, did anyone need to know about your friend going to jail

What difference does it make to you, anyway ─ is the next question?




No, in fact it is still the same question. Thanks for rephrasing it though.

unionised - 1-11-2018 at 11:59

Quote: Originally posted by Jackson  
If it evolves a gas when decomposing than you could tell by the solution bubbling

Or it is boiling.

I'm fairly sure that hypophosphite reduces copper salts- like teh sulphate- to the metal.

By the way...
https://en.wikipedia.org/wiki/DEA_list_of_chemicals

nezza - 2-11-2018 at 12:57

Hypophosphorous acid is a very strong reducing agent. It will reduce Cu++ to the metal and it will CERTAINLY reduce iodide to iodine. Phosphoric acid will do neither.

fusso - 2-11-2018 at 12:58

Quote: Originally posted by nezza  
Hypophosphorous acid is a very strong reducing agent. It will reduce Cu++ to the metal and it will CERTAINLY reduce iodine to iodide. Phosphoric acid will do neither.
Corrected for ya:P

chornedsnorkack - 2-11-2018 at 23:50

I am not confident that heating suspected hypophosphorous acid to test for decomposition is a safe idea.
Consider what the likely decay reactions are:
2H3PO2->H3PO4+H3P
3H3PO2->2H3PO3+H3P

Phosphine is poisonous.
By contrast, pure phosphoric acid should only give off pure water vapour:
2H3PO4->H7P2O7+H2O
little acid volatilized below, say, 700 degrees.

Thus testing for hypophosphorous acid should rather rely on its reducing properties.
Some tests might also be sensitive to phosphorous acid, or contamination of phosphorous or hypophosphorous acid in majority of phosphoric acid; but if the aim is to rule out pure phosphoric acid as labelled then finding reducing properties should be enough.

Mesa - 3-11-2018 at 09:39

Phosphine is not only poisonous, it combusts spontaneuously in air.
This is much more relevant hazard to be aware of when heating H3PO3/H3PO2 to decomp temps.

chornedsnorkack - 11-11-2018 at 00:56

Quote: Originally posted by Mesa  
Phosphine is not only poisonous, it combusts spontaneuously in air.
This is much more relevant hazard to be aware of when heating H3PO3/H3PO2 to decomp temps.



Not so much.
Spontaneous combustion happens because the reaction
H3P+2O2->H3PO4 is exothermic, and when phosphine is at high concentrations, it can happen with thermal runaway.

If you have hot steam with appreciable impurity of phosphine, then the phosphine being diluted with steam may be too dilute for ignition - yet still at relevant concentrations for toxicity.