Help with precipitating using SMB

[LawrenceP]

Hello,

I tried the AR method with SMB as precipitant for a small amount and it seemed to work.

However this time I tried using 700ML of AR on 100 Grams of gold skins that I got from dissolved connectors and got a nice yellow solution after the platings dissolved.

Then I used some Urea N46 till the fizzing stopped with further addition.

Now the problem - when I added SMB to the solution, I got vigerous foaming with yellow head so I kept adding SMB but the fizzing wouldnt stop and the solution remained yellow.

After about 500 gms of SMB, the solution was just a touch darker yellow and I ended up with a light precipitate at the bottom. Is that the excess undissolved SMB?

What can I do to get my gold back?

Photo of the result attached.

Lawrence P

 

[Geo]

sounds like you still have free nitric in your solution. test it with stannous chloride to be sure the gold is still in solution. if you get a positive test, filter the solution and remover the excess salt. if you have a piece of gold, you can use that to rid the solution of the nitric. place it in the solution and heat it. you should get a reaction as soon as the solution heats up. if you have no piece of gold, you can do it the hard way. it sounds as though you added way too much nitrate to start with. you can evaporate the solution down until it becomes very thick and then add hcl back to the original volume. it may take several times doing it that way to rid the nitric from solution. you can also cement any values in the solution using copper and start over with the process and not add so much nitrate or do what i do and use hcl/Cl (bleach) to dissolve your foils and powders. that way you only need to leave the solution uncovered and the chlorine will evaporate on its own, or you can heat it to steaming and drive it off in about a half hour or so.

 

[freechemist]

LawrenceP,

Did you test the "nice yellow solution" with SnCl₂, stannous chloride, after dissolution of the platings and before treating with SMB? Was there any dissolved gold detectable? Most evident to me is the fact, that you added much, too much SMB, and so created a big mess. 500 grams SMB are sufficient to precipitate nearly 700 grams of gold. To precipitate 1.00 (one) gram of gold, a minimum of 0.72 g of SMB is needed.

Regards, freechemist