Before explaining how to perform this process, it's probably be better if we first talk about why use it in the first place.
As you probably know, there are many reducing agents that will reduce ionic gold into the metal, such as: SMB (Sodium MetaBisulfite), copperas (Iron II Sulfate), Sulfur Dioxide Gas (SO2), Hydroquinone, formaldehyde, hydrazine Sulfate and many more… each has its own applications and pro's / con's.

 

5. Gold powder cleanup.


The washing process is probably the most important one as it will remove the majority of contaminates that ha been dragged out of solution along side the gold.
Metal contaminates such as Copper, Nickel, Platinum, Palladium and Silver (Chloride).

Before we start, you should know that there is some dispute regarding a direct Aqua Regia (AR) refining process for high gold content alloys, main reason for that dispute is usually the silver content, which, react with AR and convert to Silver Chloride (AgCl) and somewhat retarding the process.
Some refiners just don't like to deal with AgCl and will prefer Inquarting process to eliminate the silver (and base metals + PGM) all together prior to gold dissolution.


4 - Gold precipitation with Sodium Metabisulfite.


Now that we have our Gold solution (Chloroauric acid - HAuCl4) filtered and clean of any solid sediments it  is time to get the gold back out of the solution and precipitate it to it's metallic form.

 


The Inquartation method is one of the most common methods of refining low and medium karat gold jewelry (9K-18K) and can also serve the first step in refining sterling silver.

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