posted on Feb, 25 2012 @ 11:19 AM
As before a very interesting process. As a ChemOps in a precious metals refinery we used a some what different method for refining gold. This process
would not be practical on a small basis like this. However it is capable of producing gold of 5-9's of purity. This level of purity is suitable for
electronics,and the company I worked for used it for that very purpose. We supplied machined disc's of this material for use in a vapor deposition
process. This process involved playing a beam of electrons over the disc in a vacuum and passing a product like CD blanks through the vacuum chamber
where the gold vapor would be deposited in a thin layer.
Now as to the process that we used. The raw metal with it's contaminants would be melted and then poured into a large vat of water where it would
harden into Irregular flakes with a large surface area. The gold moss as it was called would then be sent to the refinery where we would place it into
a glass lined process vessel and add hydrochloric acid and heat it. We then had a large graduated cylinder with a glass tube attached by an acid
resistant rubber tube. This was placed into the vessel through a hole in the vessel cover for that purpose.
The cylinder contained nitric acid. The nitric would be added when the hydrochloric had been brought to temperature. We bled it into the vessel very
slowly and watched the feed rate by using the graduations and timing the feed rate over time. Slow was better as the large surface area created by the
melting process would allow the reaction to run out of control If done too fast..This was continued until the plastic tray the gold was placed in at
the bottom of the vessel floated, indicating that the metal was all dissolved.
The resulting solution was then transferred to a gassing vessel, which was also made of glass. We would usually dissolve several pounds of metal at a
time. Once in the gassing vessel we would insert a glass tube with a rubber connector into the vessel and meter sulfur dioxide gas through the tube to
bubble up through the solution. The SO2 would drive off the nitric acid and the gold would precipitate out of solution as gold won't dissolve in raw
The gassing process was fascinating to watch . As the gas pushed out the nitric the gold would start to come out of solution and would create a gold
blizzard in the vessel settling to the bottom. The vessel would become so hot that you couldn't touch the vessel without being burned.After the gold
finished coming out of solution we stopped the gas and proceeded to drop the solution into a filter designed specifically for this process. After the
solution was filtered the contaminants would be in the remaining solution. This solution was then transferred to waste tanks for further processing.
The gold was in the filter and after washing with water was shoveled into glass trays for drying. At this point the metal was referred to as gold
sponge.It looked just like the powder at the end of your process.
The metal , when dried, was sent to our vault to be used in the manufacturing process after assay. Different 9's of purity would be used in different
processes. I can remember a day when I took about 9 million dollars of pure gold to the vault. Keep in mind that at this time gold was going for about
$850 a troy ounce.
This process that you are using I've never heard of before. However it should work just fine if care is taken with handling the chemicals and
byproducts involved. I have heard of a process that uses iron fillings to precipitate the gold. I'm not real sure how it works, but, I think that it
would work by the iron dissolving into solution and pushing the gold out as a solution can only hold so much metal in a dissolved state. We used a
similar method to precipitate waste metals out of the waste solution by adding zinc moss.
All things considered your process is wonderfully simple for use on small amounts of metal. Thanks for a great thread. As in your silver thread I
would be happy to answer questions asked in a u2u if I can.