precipitating gold

[arthur kierski]

when i precipitate gold from ar solutions (used urea to eliminate nitric),many times the precipitate is grey instead of brown---could someone explain to me what happens?

 

[Oz]

I do not use urea but my first thought would be that it is contaminated. Knowing the source material would help in indentifying the contaminate. Assuming you are using SMB and that you run a lot of electronics, a grey could be a platinum group if excess SMB was used or some silver chloride if the sun got to it a bit.

Then again I do not use urea so that may do something that I am unaware of.

 

[butcher]

I would think lead? and maybe nitric is not eliminated yet either.

 

[lazersteve]

Dirty Copper I chloride can take on a gray appearance also. Try washing the gold with hot hydrochloric acid after several water rinses. If the gray substance is copper I chloride it will dissolve and color the HCl dark brown, almost black if enough is present. The gold powder will then be more of a red brown color. This can occur if the AR solution was very dirty due to excessive base metals.

Steve

 

[arthur kierski]

i will do what sugested and then give the results---

 

[Harold_V]

i will do what sugested and then give the results---

Be certain to test the wash solution for values, Arthur. It would be a shame to lose some of your gold by unexpected dissolution. Better safe than sorry!

Harold