Silver Melting and Refining

One day last week we were shown the melting and refining process of silver. We thought the process began with melting and then the refining process, but it turns out that unless the silver is pure, it has to be removed from its component elements before it can be melted.

Silver Refining - Mixing Nitric Acid with the Silver = Silver Nitrate

Refining Silver with Nitric Acid

So, they dump the silver into a vat and add nitric acid, which then dissolves the silver and its alloys. Salt (sodium chloride) is then added to this liquid, which makes the silver precipitate (coagulate) with the chloride in the salt. I remember for the final exam in my high school chemistry class, I was given a test tube of an unknown powder and told to determine what four elements were included in the powder. It turned out to be a mixture of silver nitrate and sodium chloride, which is basically this step in the silver refining process.

Silver Refining Equipment

Silver Refining Equipment

Anyway, the silver chloride is then washed, so that it is pure silver chloride. The next step is to add caustic soda (lye, sodium hydroxide) to this powder, which will react violently, creating silver oxide. Now simply add dextrose (a type of sugar commonly found in corn syrup), and the silver will be made pure, but in a form which the refiners call “cemento” (cement). We didn’t understand this bit, but from what I’ve read elsewhere, this cement is simply pure silver in very tiny granules.

Silver Melting Furnace

Furnace to Melt Silver

When we first were discussing the process with the refiner, we got stuck a couple of times trying to understand what he was saying in Spanish. Sosa, literally translated as soda, had us entirely perplexed, thinking he meant baking soda, but which actually refers to the caustic soda or lye. He told us that “azucar” was added, and we couldn’t understand how simple sugar would help in the refining process of silver. I still don’t understand, but it evidently turns the silver oxide into pure silver.

This week, the refiner is going to show us the entire process in a small batch at his shop. He’ll likely take just one or two coins — oops, I mean some old silver jewelry or bullion, since melting coins is illegal — to demonstrate the entire process. It should be very interesting, more so for me than seeing the huge process.

NOTE:  Actually, thousands of coins are melted down every single week, even coins that contain just 10% silver  The refiner told us that he melts down an average of twenty kilograms (44 pounds) of coins every single day.

UPDATE — We still haven’t seen the process with just a coin or two.  We hope to do this soon.  When we do, I’ll add a link to that blog.

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