gold precipitation notice

[sayf]

hello, happy new year

when i precipitate gold using smb or iron sulfate
(not zinc) i some times notice that some of the gold precipitant floats on the surface of the solution directly after precipitation, this gives me headache because it forces me to filter the whole solution
this thing never happens when i extract gold from ceramic cpu's the gold in their case is all at the bottom and very stable and heavy

any one have an idea why the gold precipitant may float on the surface and if there is any solution for such a problem?
thanks

 

[Lino1406]

Acetone, d=0.78 or methanol, d=0.79 will help in preipitation

 

[g_axelsson]

Just knock it down with a bit of water. I use a bottle with a pump, giving a fine mist and that makes any gold floating on the surface to sink. Or just stir the liquid, that should knock it down.

Göran

 

[sayf]

Just knock it down with a bit of water. I use a bottle with a pump, giving a fine mist and that makes any gold floating on the surface to sink. Or just stir the liquid, that should knock it down.

Göran

Thanks goran, but whats the reason for that, it is not logical, the gold has higher density so why its there on the surface, is it due to surface tension or any other reasons?

 

[Lino1406]

Surface tension of course, overcomes weight

 

[sayf]

Surface tension of course, overcomes weight

you mentioned acetone and methanol, do they accelerate the precipitation or enhance it?
Also whats the required amounts of them per gram of gold??

 

[Lino1406]

They are lighter, have lower surface tension, and can be reused, so, that depends..