Precipitation help please?

[g_opolis]

I am dealing with a rather mixed bag of donor material. Pins from 50 486 and earlier units + pins from 40 extra early hard drives & floppie drives. Seperately the ribbon cable ends from the 50 units + about 2 lbs extra. Then processed out the cpu's of the 50 units. All these were done with AP, then HCL/ clorox, then smb, rinsed 3 times HCL, rinsed 3 times water. Here is where I may have screwed up. I combined all the powder into 1 batch and redesolved in HCL/ clorox. Deep yellow. Smb dropped a clumpier precipitate this time, but the material is still very dark brown. I rinsed with HCL again and am getting a very light grey brown coloration in the rinse. Could this be excess sulfur? Am I correct that ammonia rinse would be helpful? I am very new to this, and I am trying to work out a few kinks before I move on to bigger batches. I don't have any nitric, but I suppose I should make some. One last thing, I can't find any ferrous sulphate that is viable in my town, so right now I can't try another precipitant. Any advice is much appreciated. Thanks, Robert.

 

[lazersteve]

Robert,

Dissolve some iron in H2SO4 and evaporate to form Ferrous Sulfate crystals, works great to precipitate gold.

The gray stuff sounds like silver chloride or copper chloride possibly. Copper Chloride dissolves in HCl so it's likely silver chloride which dissolves with hot Ammonium Hydroxide.

Steve

 

[banjags]

what is better/more effective at precipitating gold... ferrous sulfate or smb?

 

[phoenix_phx_]

what is better/more effective at precipitating gold... ferrous sulfate or smb?

From what I know, use FeSO4 * 7H2O when you have deep yellow.

There is equivalent to SMB (it's cheaper):

1. (SMB) Na2S2O5 + HCl --> NaCl + SO2 + O2 (or sth )

2. Na2SO3 + HCl --> NaCl + SO2 + H2O

SO2 precipitates AuCl to metalllic form (brown powder).

I think, we should wait for lazersteve's comment about mine text.

 

[g_opolis]

Thanks for the input. I'm going to wash with the hot ammonianext. This set of materials seem to be fighting to the bitter end. If only it was all as straight forward as fingers! To raise the ante, I am going to try to leach 20 lbs of very old crushed IC chips.Without the benefit of nitric, would AP suffice? Or would the amount of base metals be prohibitive? Thanks , Robert.

 

[lazersteve]

Neither is better than the other.

My experience with Ferrous Sulfate is that it will occasionally precipitate the gold as a fine shiny gold powder.

Harold has used Ferrous Sulfate way more than I have and should be the one to consult further.

I produce it when I use the iron and sulfuric acid method of reducing silver chloride (see video on my website). The left over liquid when evaporated will precipitate gold. It forms scale like green plates when evaporated undisturbed with the iron stirrer left in it. I dissolve these plates in water and add a very small amount of HCl to dissolve any residual iron compounds.

Steve

 

[g_opolis]

Thank you Steve for the recipe. I will make good use of that. Your video tutorials rock! Robert.