White powder in a/r

[martymcfly]

Hi,

I started a batch of ceramics but this time once i had fully digested all the metal i added some unwashed gold powder from another batch that i was hoping to purify a bit better but since adding my solution has brown speckles like gold powder but also has some white material forming as well. Could this be tin contamination?

I intend to continue as normal and filter it all out but was unsure what this stuff might be.

Thanks

 

[Geo]

ceramic CPU's and chips contain silver. this silver will not stay in solution for long and will precipitate out as silver chloride. chill the solution with ice as this will have two effects. first, it will cause the silver to drop faster. second, the melting ice will dilute the solution causing the silver to further precipitate own its own.

 

[martymcfly]

Thanks Geo,

Ive filtered out what appears to be silver and once i have a good amount i will set about sticking it in some nitric.




I tried dropping a drop of stannous on it and it turned it grey, im not sure if that has any relevance.

 

[lazersteve]

The yellow stuff appears to be tungsten oxide. It's very common in ceramic cpus.

It will give you a false ( cornflower blue) positive stannous chloride test.

Is the yellow powder soluble in a concentrated sodium hydroxide solution?

Steve

 

[martymcfly]

ive not tried that. I think what i will try is to incinerate all my filters ive got and reprocess everything in A/R and see whats left.