Gold Assay Control Process ?

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daicane

New member
Joined
May 3, 2013
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2
http://www.youtube.com/watch?v=6ez8vNklTSA
1. 0:42 minutes Using a control assay kit. please explain me about it.ect...
2. why does he make lead envelopes for gold.
thank.
 
1. seems to be a simple scratch test using acid.

2. lead is used as litharge ( http://en.wikipedia.org/wiki/Litharge ) when cupellation ( http://en.wikipedia.org/wiki/Cupellation ) is performed.

SOP when doing an assay.
 
The video is a summary of the cupellation fire assay process.

The lead envelopes are made using pure lead foil. In this case, metallic lead is used and not litharge. Litharge would be used in the fusion process which is prior to the cupellation and is used to collect precious metals into the lead button.

He used a simple acid test to estimate the gold content of the sample in order to determine the correct amount of silver to add (usually between a 3:1 to 4:1 silver to gold ratio is used so that the parting step proceeds correctly).

In the furnace, the lead melts and also acts as a solvent for the sample, helping it to melt. Once molten, the lead and base metals in the sample oxidize and are absorbed by the cupel (clay cup). The remaining bead is precious metal only. By the way, the cupels in the video are very black, which tells me the cupellation temperature is way too hot. Too hot a cupellation temperature causes excessive sample loss.

Once out of the furnace, the sample is rolled thin to expose greater surface area to attack from the nitric acid. The nitric acid will dissolve the silver, and if present, palladium and platinum, leaving only gold behind.

The gold left is weighed. I find fault with the video stating it is 9999 pure gold, it never is, there is always a small amount of silver retained in the gold which is why a control sample of known purity gold is analyzed side by side with the unknown so that the silver retention is determined and corrected for. This is known as a proof corrected assay.

The video is a simplified summary of the cupellation fire assay process, but not bad.
 
Westerngs said:
The gold left is weighed. I find fault with the video stating it is 9999 pure gold, it never is, there is always a small amount of silver retained in the gold which is why a control sample of known purity gold is analyzed side by side with the unknown so that the silver retention is determined and corrected for. This is known as a proof corrected assay.

The video is a simplified summary of the cupellation fire assay process, but not bad.

I also like the way you think. This can not be by 9999 gold

I'm learning refined gold from ore.I wonder whether you have been manufacturing methods are not the best pure gold?
 
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