precipitating problems

[dpg]

Hey there,
I was wondering if the temperature or air pressure has an effect on the precipitation method.
It seems , when It gets cold or when the weather is unstable the SMB has a hard time dropping it out of solution. The water stays a chocolate brown color.
I think if I let it sit a few days, it might finally drop.
Is there a solution to my problem?
thanks in advance!
Dpg

 

[Harold_V]

If your solution now tests barren, try boiling the entire lot for a few minutes, then allow it time to settle. That may be exactly what it needs. It would do no harm to add a little HCl.

Harold

 

[Platdigger]

I am curious what the added hcl may be for Harold?

Are you saying, if a solution is too basic, it would prevent the gold from coming out of solution with smb?
Randy

 

[dpg]

Hey Harold,
How's things my friend?
The funny thing is that when I test the solution it shows that there is plenty of gold still in solution, I dont think that I'm supposed to add more and more smb or do I? Thank you for your quick response!!!
always a pleasure!
Cheers,
Dpg

 

[Juan Manuel Arcos Frank]

dpg:

Harold_V is right,as always... if you see a chocolate color in your solution you have invoked such a big Devil...his name is COLLOIDS and your gold will never precipitate.Boliling the solution as Harold_V has told you is the right way...sulfuric acid works too...the colloid was formed because some contamination of organic material was present(i.e.,some kind of plastics or gelatine).Try to avoid organic material when you refine your gold.I hope this will help you.

Regards.

Manuel

 

[Harold_V]

Hey Harold,
How's things my friend?
The funny thing is that when I test the solution it shows that there is plenty of gold still in solution, I dont think that I'm supposed to add more and more smb or do I?

In this case, you may be at the mercy of the input of others. I never used SMB, so I am not familiar with its characteristics. I worked with ferrous sulfate briefly, then switched to SO2 in a cylinder. I realize you're dealing with the same reagent, but the form is different, and that's the part where I'm no help.

That you still have gold in solution, however, speaks volumes about a problem of sorts, unless you simply used too little SMB. If you have nitrates present, when you add HCl you'll re-dissolve any gold that has precipitated, but eventually the nitrates should be consumed, then your gold should precipitate completely when you introduce a proper amount of precipitant.

There's a bit of logic involved in adding HCl (or sulfuric) when you boil a solution that is slow, or refuses to settle. Often there are substances that may choose to settle out as well. By adding acid, you tend to keep them in solution. Think of it as a pre-wash to the future wash of the recovered values. It can do no harm, which makes it a good idea.

Insure that you have precipitated all of the gold before you separate it from the solution. That way you will avoid losing gold by drag-out.

Harold

 

[ppoowweerr]

I had some related questions on the SMB. These answered them spot on, Thanks again.