Sciencemadness Discussion Board

Silver Nitrate crystallization from water

golfpro - 11-9-2013 at 15:49

Today I made AgNO3 from a 3 gram or so chunck of silver, I ended up with the silver nitrate crystals sitting in the nitric acid, what I did next was a bit stupid but I did this reaction in a 50ml erlenmeyer as that's what I was limited to, I added enough water up to the neck to dissolve all of the silver nitrate and it looks milky and even a bit yellowish now, it is 65ml in a 250ml beaker sitting in the garage now, will this water evaporate eventually leaving me with Pure Silver Nitrate? I have crystalized AN from water just like this with the use of a flat cookie sheet and heat to speed up evaporation, but I don't know if I want to wait 3-7 days for the water to evaporate, I may get this into a clean flat glass pan and let this sit in darkness??

I have heard AgNO3 is light sensitive.

Ascaridole - 11-9-2013 at 16:23

The yellow isn't a bad thing, it could be lingering NO2. The concerning part is the milky white solution... 3g of Ag = .0029mol and that corresponds to about 4.7g of AgNO3, according to wikipedia (i know bad source but thats all i have right now...Ill look in the CRC when I get home) at 0ºC 1220g/L of AgNO3 should dissolve. At 50mL you should be able to dissolve about 61g of the nitrate salt. This leads me to believe you may have had impurities such as chloride or something in your water or on the walls of your flask.

As for the light sensitivity it is sensitive but not as bad as silver bromide or chloride. I wouldn't leave it out in the sun if thats what your asking.

As for purity thats questionable. You may need to filter to get a clear solution and let the clear solution evaporate.

golfpro - 11-9-2013 at 16:48

That was what I thought, a bit of NO2, it smells like NO2/chlorine. Milky is a bad word to decribe it, it's yellowish and a tad foggy, but I don't care if it's absolutely pure for the context for which it will be used.

golfpro - 11-9-2013 at 18:27

I made a stupid mistake of pouring the AgNO3 solution onto a metal cookie sheet forgetting it was very acidic from leftover HNO3 or HNO2 (don't know how much of this really forms) I was doing this to dry is and it started to eat away at the coating on the cookie sheet so I took it out and now have a brown liquid . I'll let it sit to see if they separate but besides the color, it also smells heavily of NO2, whether it is that or the crap from the cookie sheet, I don't know but I'll see what it looks like when it dries.

cyanureeves - 11-9-2013 at 18:47

what ever does not crystallize can easily be turned back to silver chloride which is what i do when i am sure i've been cheated of silver nitrate.i swear our tap water is so chlorinated it can find out silver nitrate wherever it's present.

Pyro - 12-9-2013 at 06:59

silver nitrate is yellowish after production, especially if you heat it.
mine was yellow too and it cleared up in about a week and became white

Fantasma4500 - 12-9-2013 at 09:04

the reason for that its milky (i believe this is what its usually referred to as anyways)

but why not just use your solution you have now, first let it settle with any ppt. then decant it and put some C2H2 through it (as i recall this is your only business with this compound)

DraconicAcid - 12-9-2013 at 09:23

Quote: Originally posted by golfpro  
I made a stupid mistake of pouring the AgNO3 solution onto a metal cookie sheet forgetting it was very acidic from leftover HNO3 or HNO2 (don't know how much of this really forms) I was doing this to dry is and it started to eat away at the coating on the cookie sheet so I took it out and now have a brown liquid . I'll let it sit to see if they separate but besides the color, it also smells heavily of NO2, whether it is that or the crap from the cookie sheet, I don't know but I'll see what it looks like when it dries.

Even if the solution didn't have leftover nitric acid in it, aqueous silver nitrate will react with most metals in a single replacement reaction, giving silver metal and some other metal nitrate. If the silver forms as fine particles, it will appear as a brown slime.

golfpro - 12-9-2013 at 18:05

Dumped this crap out and I'll just start over

Fantasma4500 - 13-9-2013 at 03:38

lol man you just threw 4.5g silver nitrate down the drain?

phlogiston - 13-9-2013 at 04:31

Did you use tap water? If so, next time use use distilled or demineralized water.
The 'milkyness' is a very fine precipitate of insoluble silver salts that are caused by the carbonate/chloride/other impurities typically present in tap water. (incidentally, you see similar milky precipitates when mixing tap water with solutions of soluble lead salts).

It is generally best to use only glass and plastics (although plastics may leach plastizicers/UV stabilizers/pigments/etc).

PS. You could have easily recovered/purified the silver nitrate: (1) Filter to get a clear solution, (2) precipitate silver chloride by adding a concentrated solution of sodium chloride (3) recover AgCl by settling or filtering (3) wash with water a few times (4) add sodium hydroxide to convert to Ag<sub>2</sub>O (5) wash with water (6) redissolve in nitric acid.

[Edited on 13-9-2013 by phlogiston]