Precipitating silver using Copper -vs- Salt,Lye,Sugar

[wct0415]

I am fairly new here and still reading and learning and have submitted several other posts, and the knowledge I have gleaned has been of great help. I have finished about 6 batches of Ag (15 toz)and one of Au (13 gr) and other than a few minor problems all has come out quite well. All until my last batch of Ag. All seemed to go well all the way through to the melting and pouring process. All my previous poured 1 Toz bars came out looking very nice, poured good and smooth. However my last pours look like the molting silver is cooling off too quick and the bar is rough and seems to mound up rather than flow out to a smooth finish. So I am under the assumption that I have some contaminant that is causing my issue. Please correct me if I am wrong.
To test my theory I took one of my previous successful poured bars and melted it and re-poured and all was just as I expected, nice and smooth. This contaminated batch of silver nitrate was precipitated with copper, filtered and decanted as I have done in past.
So I ask
1) what type of contamination might this be
2) and would redissolving into solution and precipitating using Au chloride method (salt, Lye, Sugar) possibly drop the silver and leave the contamination in solution.
I do understand that a silver cell will take out what ever contamination this may be , however my thinking is to start out using as good of quality silver as I can so as not to contaminate the cell solution as rapidly and transfer this to my cell as well. If the contaminate is of a PGM type, I will just use the cell to remove it, however if it is tin or lead I would like to try to remove it prior to the Ag cell stage.
Any thoughts and help would be greatly appreciated. Thanks

 

[Harold_V]

Without analysis, it may be difficult to predict that is causing your problem, but keep in mind that molten silver absorbs nine times its volume in oxygen, only to be expelled upon cooling. If cooling occurs too rapidly, the surface may not have sufficient time to settle and become smooth. I'm not suggesting that that is true in your case considering you get repeatable results, both good and bad, by re-melting. You likely do have contamination of sorts, which, as you allude, would be removed in a silver cell.

A couple things to consider. Traces of copper limit the absorption of oxygen, so bars that are very tranquil may contain some copper, whereas those that are rough may not.
You may be including some lead in your silver, albeit inadvertently. I expect it would yield problems, although I am not familiar with what they might be.

Running your silver through a cell is really a good idea if your goal is pure metals. That's particularly true if you process wastes that may contain traces of the platinum group. Once combined with silver, they are not easily removed. Simple when recovered by parting the silver, however.

Harold

 

[wct0415]

Thanks Harold
Do you think given the contaminants that either one way of dropping the silver out of solution would be better that the other

 

[Harold_V]

I favored cementation with copper. It is, by far, leaps and bounds better, in my opinion. Bear in mind, I processed a considerable amount of gold that contained platinum and/or palladium, so, to me, converting to silver chloride made no sense. I used the silver as a carrier, intentionally. If you feel you can control lead, which may or may not get washed out of silver chloride if it is in the way of a sulfate, silver chloride may be to advantage in some way----but I always found it less than convenient----I converted very little silver to silver chloride by choice.

Harold

 

[sena]

I favored cementation with copper. It is, by far, leaps and bounds better, in my opinion. Bear in mind, I processed a considerable amount of gold that contained platinum and/or palladium, so, to me, converting to silver chloride made no sense. I used the silver as a carrier, intentionally. If you feel you can control lead, which may or may not get washed out of silver chloride if it is in the way of a sulfate, silver chloride may be to advantage in some way----but I always found it less than convenient----I converted very little silver to silver chloride by choice.

Harold

hi, iam new to this blog , i used to process xray flim where i end up with silver chloride from nitric leeach , then using zinc chloride to preciptate Agcl , the yeild was quite low than using sulphuric acid/zinc , but the metal was brighter `and 95% pure , but the sulphuric acid/zinc method had quite quantitative advantage.