# Powder Washing



## -&gt;Mikey&lt;- (Feb 21, 2009)

When you boil your powder and hcl then water numerious times, does that clean the silver or any other pgm in the gold? 
Or does everything unwanted get left behind after the second refining. 
And whats purpose of the ammonia wash.


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## lazersteve (Feb 21, 2009)

Mikey,

The acid wash will remove most of acid soluble impurities that get dragged down with the gold powder when it is precipitated. Harold has pointed out that you can use a single extended boil in HCl with the same results. I use three washes as a minimum for all washes as this is a rule I learned in Chemistry class. This spent wash should be tested for values as sometimes gold and other PGMs can get in them if the gold powder contained any residual oxidizers. Incineration can help avoid this problem also as it can destroy the residual oxidizers and also oxidize any other metals that may cause filtration problems when the gold is dissolved a second time to further refine.

The ammonium hydroxide wash removes silver chloride that is in the gold powder that may have made it past your filters or precipitated when the acidic solution was diluted. This spent ammonium hydroxide wash solution should not be combined with the spent acid wash(es) as any gold chloride that is in the acid washes could combined with the ammonium hydroxide and form fulminating gold (explosive!!) . Additionally, the spent ammonium hydroxide washes should be acidified with HCl after they are used to precipitate any dissolved silver chloride. If an ammonium hydroxide solution that contain silver is allowed to dry out, fulminating silver (explosive!!) can be formed.

Steve


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## -&gt;Mikey&lt;- (Feb 21, 2009)

Thanks fer the quick responce.
Learn of like 10 new hazards everyday with each step in the refining process.


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## Noxx (Feb 21, 2009)

Concentrated HCl will dissolve silver chloride. 

But Ammonium Hydroxide wash is advised to dissolve other impurities.


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## Lou (Feb 21, 2009)

Yes, and a blue coloration indicates copper contamination. It's a pretty sensitive test, and very convenient for checking if your gold has copper in it.


Louis


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## Harold_V (Feb 22, 2009)

Lou said:


> Yes, and a blue coloration indicates copper contamination. It's a pretty sensitive test, and very convenient for checking if your gold has copper in it.


Indeed! It was interesting to see that well washed gold still contained traces of copper. 

Once you've been through the drill of washing well, and finding you still have traces of contamination, the concept of a second refining to improve quality starts looking like the right idea. It does wonders to the quality of your gold, assuming you don't shortcut the processes. 

Most likely everyone has seen this picture, but I haven't posted it for a few weeks. Can't speak for anyone else, but I never get tired of seeing it. 

Harold


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