? Ag crystals from nitrate solution containing PGMs

[kurt]

Ok if I understand what I have read about setting up a silver cell – the electrolyte needs to be made from a 98 pure or better source of Ag.

So my question is – If I have an Ag nitrate solution that is testing positive for Pd & Pt & I evaporate the solution enough for it to form some crystals – will the crystals I get be a high purity of Ag nitrate crystals – or will my crystals be contaminated with PGM salts as well

My assumption is that I would get high purity Ag crystals – as it would take the addition of HCL – then evaporation to remove free nitric (& water) & then the addition of ammonium chloride & sodium chlorate to form the PGM salts

To clarify – I would evaporate the nitrate solution just enough to effect some crystal growth but not so much as to remove all water – which should keep the Pd & Pt in solution, as well as some silver.

Kurt

 

[butcher]

I believe
The crystals would grow purer (by re-crystallization) than starting solution, but that does not mean that they would not entrap impurities as they formed, or drag down some impurity.

Edit to add thoughts;

This would seem like a very hard method to purify your silver, re-crystallizing the silver many times to increase its purity, cementing and the Thum cell, and processing the anode sludge, seems easy compared to a re-crystallization method.

Depending on your source of silver, and where its been, and unless you melted platinum with a lot of silver (10 x) there probably would not be much platinum in your silver.

 

[nickvc]

Kurt as usual Butcher is right this material isn't ideal for your electrolyte. My advise for what it's worth is to cement your silver and PGMs out of this solution and use them as your feedstock for your cell and use some clean sterling silver to dissolve, cement and wash well and then redissolve for your electrolyte. All electrical refining methods need high quality/ purity for good results feedstock needs to be at least 98% to get fine metals out, it's the same as using AP on e scrap to remove base metals before actually refining the gold to avoid contamination.

 

[Harold_V]

Ok if I understand what I have read about setting up a silver cell – the electrolyte needs to be made from a 98 pure or better source of Ag.

So my question is – If I have an Ag nitrate solution that is testing positive for Pd & Pt & I evaporate the solution enough for it to form some crystals – will the crystals I get be a high purity of Ag nitrate crystals – or will my crystals be contaminated with PGM salts as well

My assumption is that I would get high purity Ag crystals – as it would take the addition of HCL – then evaporation to remove free nitric (& water) & then the addition of ammonium chloride & sodium chlorate to form the PGM salts

To clarify – I would evaporate the nitrate solution just enough to effect some crystal growth but not so much as to remove all water – which should keep the Pd & Pt in solution, as well as some silver.

Kurt

In truth, that works. If you were to do a couple iterations, you'd have virtually pure silver as a result. Certainly pure enough for electrolyte. However, what butcher said is true---there will be minor drag-down, and some may get included in the crystals that form--but each iteration will lower the contaminants significantly. Several iterations, using distilled water, one might actually produce some very high quality silver nitrate crystals. It isn't a bad way to produce pure silver nitrate when other means may not be at your disposal.

For the record, clear ice is formed that way. Circulating water is introduced to a frozen sheet, where ice slowly forms. Impurities in the water are rejected, yielding, for all practical purposes, pure water. The ice is clear.

Harold

 

[kurt]

Thanks Harold - I figured it would work - it just seemed to make sense when I thought it through & yes I figured it would take a few iterations to get some good clean Ag nitrate crystals which should be easy enough to test with stannous after each iteration (just AgCl with no colors indicating PGMs)

The reason I asked was right now the only silver I have is from this batch of points & it's indicating PGMs - however I just talked to a buddy that has some 999 & he said he would loan me some I just need to return silver when done.

I have not yet set up &/or ran a cell so this is going to be new to me. I have done a lot of reading but I am still going to have some questions about it - it may be a few days as I have other things going on first.

Kurt