Cant seem to drop the gold correctly

[Harkey1]

Cool Thanks Steve

 

[butcher]

Try giving it a boil and let cool, add little HCL, if you already have more than enough SMB you should smell SO2 gas, if not try some more,, if all else fails I would not throw out gold, cementing with copper is easy,
You stated your solution was not loaded with base metals so that should not be the problem, any organics in solution? To cause colloids?

Just letting sit for a while does not necessarily mean the oxidizers are depleted.
Never- Evil asked is that sodium metabisulfite or a sulfate? Was it stored dry in closed container?
Adding a pinch to a test tube with dilute HCL do you get SO2 gas?

Have you tried making and using ferrous sulfate?

 

[eagle2]

Yes, SMB should always be tightly closed. It does gradually decompose. Dissolve it in warm water before using and filter away any residues. The residues are the decomposed SMB and are useless.

If you are getting a black cloudy result, that is reluctant to settle, two things are likely wrong. 1. You always should precipitate from hot solutions. This will cause larger particles to form and settle easier. Most of the time I let it settle overnight anyway. 2. The solution is too acid or too basic. The best Ph is about 1-3. Too acid and you will not get a complete precip. and what does form tends to re-dissolve back into solution. Too basic and it will be colloidal with a lot of other contaminates and base metals mixed in.

Tin is always the main contaminant when using SMB, because this is the Ph where it self precips. So if you are adding some Hydroxide or Carbonate to raise the Ph and start to see a white cloudiness, that is a Tin compound forming. Let it FORM completely, settle and filter it away. You will have a cleaner and easier SMB precip. next. ( and you are now at the RIGHT PH for SMB!!! )

Always do these operations with hot solutions. Everything just works better with cleaner results.

If you don`t even use Ph paper, with experience you can watch the color changes as you add HCl or Hydroxide and know approximately where you are.