Sciencemadness Discussion Board

Diammonium Phosphate !!

rstar - 25-10-2012 at 09:45

I brought some fertiliser that contained diammonium phosphate(DAP). but the fertiliser was granular and not perfectly white.

I tried to dissolve the stuff in water and filtered the solution. I added cuso4 to it and got cu3(po4)2 precipitate out. this means it contains DAP.

What will be the product if i heat it?
But is there anything else interesting to do with it ?

Salmo - 25-10-2012 at 10:19

You could obtain some phosphoric acid adding dry cu3(po4)2 to sodium bisulfate powder and than heating and dry distilling the mixture. I don't know if this would work, anyway I would try.

Endimion17 - 25-10-2012 at 14:36

Quote: Originally posted by Salmo  
You could obtain some phosphoric acid adding dry cu3(po4)2 to sodium bisulfate powder and than heating and dry distilling the mixture. I don't know if this would work, anyway I would try.


That's a neat way to destroy an otherwise great distilling flask so I wouldn't try it. you can't distill phosphoric acid.
Hot phosphoric acid eats glass, and on heating turns to metaphosphoric acid which I've personally heated to red glow a few times. It's a stubborn goo that also omnomnoms glass and solidifies into very hard, glasslike material. If you pour it while it's solidifying, you can make very sharp shards that cause extreme pain if they cut or pierce your skin. It's because of the acidity. I wouldn't like to be stabbed with that.

Inorganic phosphorus chemistry is fucked up.

Vargouille - 25-10-2012 at 14:58

Well, you can try to purify the (NH4)2HPO4 with a few recrystallizations. And technically, the Cu3(PO4)2 only means it's a phosphate salt. To know that it's DAP, test the pH and whether adding NaOH leads to a noticeable smell of ammonia.

rstar - 25-10-2012 at 19:34

Well i forgot to mention that, the filtrate is very very slightly cloud and has a kinda beige color rather than being clear like h2o.

I added Naoh to the solution and got a bad smell (s**t like)

Can i thermally decompose it ? Wht products shall be formed then?

Well, i think to add nacl to it, and later sublime off the nh4cl

[Edited on 26-10-2012 by rstar]

blogfast25 - 26-10-2012 at 11:27

rstar:

Try not to use 'text message inglish' to chemical formulas: this is supposed to be a science forum. :)

Vargouille - 26-10-2012 at 12:08

A smell similar to feces upon addition of sodium hydroxide? That's quite odd. In any case, it implies a significant contaminant. I would suggest recrystallizing it and then retrying several of the tests of it being DAP: Smell of ammonia upon addition of NaOH, formation of a blue or green precipitate upon addition of a copper salt, formation of a tannish to brown precipitate upon addition of an iron (III) salt, and formation of a purple precipitate upon addition of a cobalt (II) salt.

Salmo - 26-10-2012 at 13:33

Bad smell = ammonia gas you obtain
the reaction is:
(NH4)2HPO4 + 3NaOH = Na3PO4 + H2O + 2NH3

Anyway sorry for the bad idea, distilling phosphoric acid is not a good idea.

rstar - 27-10-2012 at 04:12

Well one noob question:
How does ammonia smelll like ? :D

blogfast25 - 27-10-2012 at 05:52

Quote: Originally posted by rstar  
Well one noob question:
How does ammonia smelll like ? :D


In concentrated form (SG < 0.9, conc. 30+ w%) it’s extremely pungent, almost unbearably so. It’s one of these compounds (like H2S) that we’ve probably, evolutionary speaking, developed a high sensitivity for because it’s a tell tale sign that food is going off (rotting proteins emit small amounts of NH3). In small amounts think rotting fish or very stale urine. Bweurk!

Vargouille - 27-10-2012 at 06:07

It's really hard to describe the smell of ammonia, or anything, really. It's a biting odor, but not in the same as is HCl. In short, it's easiest to just say "Get a bottle of Windex or a jug of cleaning ammonia and give that a wiff". And truly, that's what I would do if I didn't know what ammonia smells like, and Windex is pretty useful for cleaning windows, too.

rstar - 27-10-2012 at 22:42

Oh well, i remenber that i had some NH4Cl. Gonna add NaOH to it and sniff. :)