AR very dark brown after gold precipitaion

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wisco_gold

Well-known member
Joined
Dec 11, 2022
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60
Location
Wisconsin
So as the title says my aqua regia is reacting with stannous chloride to produce a very deep colored brown after I precipitated gold from solution. I do not feel that Ibrecovered nearly the amount of gold Inshould have considering how much went in..

I started with a mixed bag of mil spec pins, connecters and plated diodes. I dissolved the base metals first in nitric acid and then dissolved the flakes in aqua regia, treated solution with sulfamic acid until there wasno more reaction and then preciptated with smb dissolved in hot water. When I seen the underwhelming amount of gold dust I tested the solution and its a very dark brown. Ive read conflicting reports on what it could be so would like the current consensus if anyones willing?
 

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wisco_gold said:
So as the title says my aqua regia is reacting with stannous chloride to produce a very deep colored brown after I precipitated gold from solution. I do not feel that Ibrecovered nearly the amount of gold Inshould have considering how much went in..

I started with a mixed bag of mil spec pins, connecters and plated diodes. I dissolved the base metals first in nitric acid and then dissolved the flakes in aqua regia, treated solution with sulfamic acid until there wasno more reaction and then preciptated with smb dissolved in hot water. When I seen the underwhelming amount of gold dust I tested the solution and its a very dark brown. Ive read conflicting reports on what it could be so would like the current consensus if anyones willing?
Click to expand...
How did you use the Sulfamic?

How much Nitric did you use?

How did the solution react to the SMB?
 
Yggdrasil said:
How did you use the Sulfamic?

How much Nitric did you use?

How did the solution react to the SMB?
Click to expand...
Sorry for the delayed response; I dissolved the sulfamic in hot water (about a 1/4 cups worth) and added slowly as it was slow to react but when it did it di so violently.

Initially to dissolve the base metals I used a cup of 50% nitric acid in total. I placed the plated material in a mason jar and covered in distilled water and added the nitric until it had a nice reaction going, using almmost a full cup by the end. In my aqua regia ibdidnt use much at all, I dont think it couldve been an 1/8th of a cup.

The solution reacted somewhat strongly with he first small pour of smb, but then only light fizzing after.
 
eaglekeeper said:
How much gold plated pins did you start with?

How much gold solution did you have and how much SMB did you use?
Click to expand...
A half pound of pins and sone other mil spec plated items. Almost all of which were magentic. Apprx 3 cups of gold solution and I went heavy on the smb....apprx five grams.
 
lazersteve said:
Heat the solution to drive off all odor of SO2 then allow to cool and retest with stannous. Palladium can show as brown on stannous test and it's presence can be confirmed on a small volume of the solution with DMG.

Steve
Click to expand...
Ok I will try this now and see what happens. I have read that palladium was a possibility but I didnt rhink anything I processed in that batch would contain palladium. Well i guess maybe the little chip looking thingsin the diodes. They were extremely shiny metalic silver before being processed.
I will have to purchase some DMG as I do not have any. Unless I could synthesize it easy enough.

D
 
wisco_gold said:
A half pound of pins and sone other mil spec plated items. Almost all of which were magentic. Apprx 3 cups of gold solution and I went heavy on the smb....apprx five grams.
Click to expand...

Do you have pictures of the pins. Where did you get the pins from, because the term Mil Spec is sometimes over used.

How much were you expecting to recover from a half Lbs of pins?
 

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