too much SMB?

[Harvester3]

Hey you all,
So, is it possible to add too much SMB to drop gold powder from AP solution? As I was adding the SMB, you could see the brown particles appear as I stirred the solution. It became very dark in color, then suddenly cleared up and nothing dropped. What have
I done? Seriously, it was my understanding too much SMB was not possible; did I misunderstand?
Help is appreciated and welcomed.
Thanks
Jim

 

[nicknitro]

Hello,

Did you get any precipitant? Like white powder, possibly copper chloride?

I think you may still have some peroxide reacting with air, did you retest solution with stannous?

Small amounts of gold can be hard to precip out of diluted solutions, especially if the PH is off. They can also be easily lost with other precipitants.

Keep us up to date.

P.S. there are numerous posts as of late stateing issues with AP and SMB dropping, maybe they could be of interest. If you are not worried about contamination as of yet, which I assume, maybe try another precipitant for this solution, say ferrous sulphate? Then when you recover your gold, re-refine it, with washes and either AR or HCL-CL.

Either Way I wish you the best Bud,
Nick

 

[Harvester3]

Thanks Nick,
This auric chloride solution held the foils from 400 grams of fingers. it's strange because I've done this with far less values. As I added the SMB, you could see the brown particles in solution as I stirred, but all of a sudden it went clear and ultimately became light green. No precipitant.
Thanks for your help. I don't get to do this every day and at my age it's easy to get rusty, especially with chemistry.
Jim

 

[firewalker]

There was to much clorine in the solution and the gold desolved again.

Couple af ways to reduce clorine - dilute the A/C. I ususally add 3 times as much water to dilute the mix

I have put the mix on a hotplate and heated for a while to boil off the clorine.

Good luck....Jack

 

[nicknitro]

This was an AP solution right?

Or after AP dissolved the foils in HCL/CL, and that is where you are haveing problems.

I thought you meant HCL / Peroxide = AP, which is why I suggested there may be very little gold in solution for adding so much water and SMB.

Either way , a descent heating may be your answer as well, as Jack stated.

If your just haveing problems getting the gold out of AP, save it, rejuvenate it with more peroxide or bubbled air, and consider it your piggy bank. Break it when you feel it is ready. :lol:

Good Luck,
Nick

P.S. Anyone ever had better luck with covering solution after adding SMB? I wonder if this would help the sulphur dioxide drop the gold better/faster.

 

[gscotthack]

Hey you all,
So, is it possible to add too much SMB to drop gold powder from AP solution? As I was adding the SMB, you could see the brown particles appear as I stirred the solution. It became very dark in color, then suddenly cleared up and nothing dropped. What have
I done? Seriously, it was my understanding too much SMB was not possible; did I misunderstand?
Help is appreciated and welcomed.
Thanks
Jim

I've had the same thing happen with AR. Got a good chocolate brown and then ... too much SMB and it clears up, goes kinda yellow, nothing drops. Not sure how to recover. I have boiled down before only to boil gold away (as I was told by one experienced individual would happen if boil ... evaporate he says).

It seems like you can add too much SMB but I'm not sure why or how to recover.

 

[g_axelsson]

If you have too much SMB, try to add some HCl, it will break down the SMB and release SO₂ which precipitates the gold.

SMB needs acidic conditions to work and if there is no acid there is no precipitation... at least that's my experience.

Too much SMB might precipitate copper chloride as a white crystal mass if you have a lot of copper in solution, but that can be easily washed away with HCl.

Normal amount of SMB is one gram of SMB for each gram of gold you have in solution.

But from the description it sounds like you have remaining oxidizer (nitric acid, chlorine, hydrogen peroxide) in solution, it will redissolve the gold. The gold starts to precipitate and then it goes into solution again. In this case you have to do a proper denoxing (evaporation and additions of HCl for example) or remove the oxidizer you used.
... or fight it with additional additions of SMB, but that can be a quite drawn out battle. Been there, done that.

Göran