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Gold to its carat

Sir,

I have refining workshop and I refine gold by adding silver double weight of gold and melting it making small granules and boiling it with nitric acid until all impurities are dissolved in acid gold becomes powder and then washing the powder neatly then melting the powder gives me 99.20 purity gold. Sir if you have any procedure please post it. Sir I want to know how we can purity of gold up to 99.80-90%. is there any other chemicals to be added or acid any to increase the purity to 99.60-70-80-90 %.

Waiting eagerly,

VS Shutherr
refinings - Quilon, Kerala, India
2003

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As you have completed most of the refining, and have melting equipment, I suggest flame refining. Use an oxidizing flame on the surface of the molten gold for 1/2 hour. Impurities will form oxides that can be skimmed off.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2003

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2003

Dear Mr.Shutherr,

The process you have outlined is Nitric Acid parting. The best you can get with this process even with the fire refining method described in the next thread would be 99.5% purity. You really need to upgrade your process using Aqua Regia and a suitable reducing agent like Sodium Meta Bisulfite to precipitate the gold. Properly done, this process will yield 999.5 to 999.9 fine gold. There are 2 excellent books available on refining precious metals available from International Precious Metals Institute (IPMI) as follows: Refining Precious Metal Wastes ⇦ on eBay or AbeBooks or Amazon [affil links] by C.M.Hoke and Small Scale Refining of Jewelers' Waste ⇦ on eBay [affil link] by Roland Loewen. The information in the books will explain in detail the processes used for refining gold. Most of the small refining operations I visited on many trips to India were using Nitric Acid parting or if aqua regia dissolution was done, ferrous sulfate ⇦ this on eBay or Amazon [affil links] was the reducing agent. I made many suggestions about upgrading the processes but most fell on deaf ears.

Good Luck & Best regards,

Jim Sivertsen
United Precious Metal Refining Co. Inc. - Alden, New York, U.S.A.