gold platted pin

[naandesh]

dear friends,
now hope all are safe and healthy, i am try to understand how to refine gold plated pins. i was try many times but still complicated. when i put gold plated pins in nitric acid all plating was removed from copper pins then filtered with paper but gold contaminated with some gray powder. how can i remove this gray slug from gold flaxs? i try with diluted HCl but some gold loose due to nitric reduse. i also try AR for it but recovered gold quality very poor. please help me....
thanks with regards

 

[FrugalRefiner]

i also try AR for it but recovered gold quality very poor. please help me....

That would be my suggestion. Your first step in dissolving the base metals and filtering the foils is a recovery process. The goal is to separate the values from most of the base metals.

Then, you refine the gold by dissolving all the solids and selectively precipitating the gold with something like SMB or ferrous sulfate (copperas). If the quality of the gold after a first refining is poor, redissolve the gold a second time and precipitate with a different reducing agent.

Dave

 

[nickvc]

I suspect you have tin in your foils as stannous which will follow the gold into solution, once you have your foils try incinerating them first and then use HCl to remove the tin oxide wash thoroughly and then dissolve your gold.

 

[naandesh]

i also try AR for it but recovered gold quality very poor. please help me....

That would be my suggestion. Your first step in dissolving the base metals and filtering the foils is a recovery process. The goal is to separate the values from most of the base metals.

Then, you refine the gold by dissolving all the solids and selectively precipitating the gold with something like SMB or ferrous sulfate (copperas). If the quality of the gold after a first refining is poor, redissolve the gold a second time and precipitate with a different reducing agent.

Dave

thanks dave, for your valuable suggestion.
I explain my process in short, first all base metal dissolved by nitric acid then filtered with filter paper, collate dry sludge wash with hot water 2 or 3 time test PH level of water its neutral then wash with diluted HCl. again filter the solution. remained material separated in beaker adding concentrated HCl gold particle clearly visible. then add HNO3 drop by drop. stop adding HNO3 when all gold dissolve. then filter this solution and boiled adding urea to check all nitric are gone. I try SMB, FeSO4, and now I satisfied with Hydrazine H4N2 (4AuCl3 + 3H4N2 → 4Au + 3N2 + 12HCl). its right way? please share your opinion.. by the way my question base on shorten the process mostly I use gravity filtration its take time. and if i filter the solution 5 to 6 time its very time consuming. i want to know how to collect clean gold flax in first step?
thanks with regards

 

[FrugalRefiner]

I explain my process in short, first all base metal dissolved by nitric acid then filtered with filter paper, collate dry sludge wash with hot water 2 or 3 time test PH level of water its neutral then wash with diluted HCl.

You could be putting a small amount of your gold into solution here. Even with thorough washing, some nitrates can remain in your filtered material. Adding HCl could produce a small amount of AR, which could dissolve a bit of gold, which could be lost when you filter it again.

again filter the solution. remained material separated in beaker adding concentrated HCl gold particle clearly visible. then add HNO3 drop by drop. stop adding HNO3 when all gold dissolve. then filter this solution and boiled adding urea to check all nitric are gone. I try SMB, FeSO4, and now I satisfied with Hydrazine H4N2 (4AuCl3 + 3H4N2 → 4Au + 3N2 + 12HCl). its right way? please share your opinion..

I have no experience with hydrazine, so I can't comment on its use, other than to say it is quite hazardous.

by the way my question base on shorten the process mostly I use gravity filtration its take time. and if i filter the solution 5 to 6 time its very time consuming. i want to know how to collect clean gold flax in first step?

If it were mine, I wouldn't spend all the time filtering and washing your material. Once you've dissolved the bulk of the base metals, you can let the solid material settle, then decant the solution. Your next step is going to be to dissolve the gold, so any minor amount of nitrate left in the solids and the small amount of solution remaining with them should be consumed in making up the AR you're going to use to dissolve the gold. Add your HCl and allow it to react. If more nitric is needed, it can be added.

Once all the gold is dissolved you can filter to remove any undissolved material, then drop the gold with your choice of reducing agent.

Dave