Had a bit of a hiccup using aqua regia for the first time to recover gold from concentrates. Just want to run this by more experienced folks to ensure that I'm not missing something.
Made some beautiful aqua regia with muriatic acid and concentrated nitric acid with a 4:1 ratio. Let concentrates soak for a day or so with regular mixing. Then, poured off and filtered aqua regia into glass jar. Next step is where I had a misstep.
Next, I added SMB to filtered AR neglecting to neutralize nitric first with urea. Realized my mistake (eventually) when the gold that started to drop out of solution immediately re-dissolved into solution. After recognizing my error, I added urea to aqua regia slowly until the urea no longer reacted with solution. As I added the urea, solution color started to change to a golden yellow color and brown powder precipitated out of solution. Assuming that brown powder is the gold. After fully neutralizing nitric with urea, I added additional SMB until it no longer reacted. I likely added too much SMB in the end. In addition to brown powder, white material also precipitated out of solution. So, now I have both brown powder and this white material collecting on the jar bottom. I'll let this sit for a day or so.
Due to my error, will there be any foreseeable problems/complications washing the precipitated gold first with muriatic acid and then water and otherwise preparing the gold for melting? Should I consider redissolving any precipitated material in fresh AR and then reprecipitate gold more carefully?
Made some beautiful aqua regia with muriatic acid and concentrated nitric acid with a 4:1 ratio. Let concentrates soak for a day or so with regular mixing. Then, poured off and filtered aqua regia into glass jar. Next step is where I had a misstep.
Next, I added SMB to filtered AR neglecting to neutralize nitric first with urea. Realized my mistake (eventually) when the gold that started to drop out of solution immediately re-dissolved into solution. After recognizing my error, I added urea to aqua regia slowly until the urea no longer reacted with solution. As I added the urea, solution color started to change to a golden yellow color and brown powder precipitated out of solution. Assuming that brown powder is the gold. After fully neutralizing nitric with urea, I added additional SMB until it no longer reacted. I likely added too much SMB in the end. In addition to brown powder, white material also precipitated out of solution. So, now I have both brown powder and this white material collecting on the jar bottom. I'll let this sit for a day or so.
Due to my error, will there be any foreseeable problems/complications washing the precipitated gold first with muriatic acid and then water and otherwise preparing the gold for melting? Should I consider redissolving any precipitated material in fresh AR and then reprecipitate gold more carefully?