with out using precipitant?

[AurumShine]

I Dissolve gold plated pins in aqua regia (hcl,hno3) after dissolving dilute and filter aqua regia . then evaporate 3 times adding hcl and few drops of sulfuric acid but real problem is when last evaporation solution like syrup when it cool the solution convert into crystals then i add water and stir well gold flake and silver crystal visual with out using precipitant and some gold powder and silver in the bottom then i test solution with stannous cloride the test is nagative what can i do ???

 

[oef62nd]

For plated items you need to use a cell.....to get the plate off..plate is so thin...very little gold there. got to do big load...

Good luck use a cell next time

 

[Harold_V]

I have commented time and again that it is not a good idea to process pins, or plated items that have a copper base, in AR. The problems that accompany that kind of process are endless, and often result in the loss of values. Not lost, really, for they are generally still there, but have been precipitated prematurely, as you have experienced.

It would be in your best interest to strip the gold from pins prior to dissolution, or to dissolve the pins in either nitric, or HCl. Nitric is very fast, but can be expensive. If you have time, use the HCl process.

I strongly advise you use AR only when you are dissolving values from non-metallic substances, or under particular circumstances, where you allow it to dissolve the base metals to a point, than allow the base metals to cement the values from solution, at which time it can be discarded. That way you can eliminate the base metals instead of carrying them through the process to the end, which is troublesome in many cases, as you've discovered.

Harold

 

[AurumShine]

THANK,S SIR Harold and oef62nd. I read c.w amen book he wrote in his book three time evaporate solution and add hcl but last evaporation solution like syrup then add water why?? add water why not add hcl i think that if i add water the solution goes to weaker .
when i do last evaporation recently add hcl not cool down .because it convert into crystals.