# Washing the gold powder after using SMB



## lazersteve

All,

Lately I've been swamped with people asking me how to wash the gold powder so here's a quick tutorial on how I handle it. This process is a variation of Harold's wash procedure.


 After precipitating the gold with SMB, test for gold in solution with stannous chloride, if present (purple swab) add more SMB until test is negative.

Here's how stannous looks to Gold, Platinum, and Palladium







*Note the color of the results will be lighter if the concentration is low. The colors will also vary if you have several of the metals in the same solution.*

Let the gold powder settle to the bottom of the beaker over night.

Siphon or gently pour off the used SMB solution into an old milk jug labeled Used SMB. Save in your stock pot or properly dispose of.

The gold powder stays in the same beaker you precipitated it in.

Add just enough water to cover the gold powder and boil for 5 minutes (Removes undissolved and water soluble salts)

Let settle and pour or siphon off the water into the stock pot.

Repeat three times.

Add just enough muriatic acid to cover the gold powder.

Boil until the acid is no longer discolored by the process and pour or siphon off into the stock pot after testing with stannous. If gold is present keep in separate beaker to precipitate later.

Repeat the water rinse as above.

If you suspect silver is present as a contamination, repeat the process with hot 3% household ammonium hydroxide (unscented- clear). Put these rinses in a separate container and add muriatic acid until no more white silver chloride precipitates. You have added enough HCl when there are no more white fumes coming out of the liquid. Any karat, dental, cpu lid, or gold filled scrap will have silver as a contaminate.

Finish up the rinses with three more hot water rinses. Put these rinses in with the ammonium hydroxide rinses.

Gently heat the beaker containing the gold powder while swirling the beaker. As the gold dries it will begin to clump and move around the beaker freely. Don't allow the gold to stick to the beaker. 

When the gold is 100% dry it should be a nice light tan color, if not redissolve it and precipitate again with SMB. Repeating the above cleaning process after precipitation. Good clean gold settles very quickly when precipitated and clumps into nice balls when dried. No gold should be stuck to the beaker when you are done.

When completed transfer the gold to a properly prepared melting dish and melt into a button.

Steve


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