quicksilver77PM.
You are asking for Harold's gold washing procedure., it can be found in the topic getting gold pure and shining in the help needed section.
I am a bit confused by your question, you state you are using HCl (or possibly the copper II chloride leach) to depopulate circuit boards, and say you have black powders, and are asking for a procedure to wash gold powders,
I am having a hard time understanding your question.
My question first is why would you, or did you dissolve gold with this mess? Tin problems, with high loses of gold, come to mind if you did put gold into solution with the solder...
Cadmium chloride is very soluble it would be in solution if you did have cadmium chloride dissolved.
Lead chloride is pretty much insoluble (a white powder), that becomes fairly soluble in boiling hot water, and dissolve clear in boiling water and will crystallize back out of the water as white lead chloride crystals upon cooling of the wash solution.
Silver chloride (also a white powder unless rinsed of high HCl acidic solution and exposed to sunlight where it can darken as it partially converts back to silver metal), silver chloride remains pretty much insoluble as a chloride even in boiling hot water, it can be fluffy and can take time to settle so allow for the silver chloride to settle as you wash out the lead with boiling hot water.
Silver Chloride will not dissolve in nitric acid, if for some reason you needed to dissolve it you could, (but some processes used here can be dangerous if not done right, so I will not go into detail here). Besides if silver chloride was in these black powders ( and these black powders were in fact gold), at this point I would dissolve the gold from the silver chloride with a second refining, leaving the insoluble silver chloride to deal with later (keeping them wet in your silver chloride collection jar).
If the black powders happen to be metallic silver (converted by light from some of the silver chloride powder), only the portion of silver that did convert to metal would dissolve in HNO3, the remaining silver chloride would not dissolve in HNO3.
If you did not dissolve gold, and you rinsed or diluted the white powder that may explain the black colors of the powders, partially converted silver chloride exposed to light.
NaCl sodium chloride is also water soluble, its solubility does not change much at different temperatures.
Most chlorides are soluble, check the solubility rules for a better understanding of the chemistry involved here.
If those black powers are gold, you should refine them again.
I am still baffled by the question, did you use too much oxidizer and put gold into solution with base metals? From what you stated you were trying to do, you should not of had black powders of gold, and if you did while the tin solder was in solution I would expect high loses due to colloidal gold solutions...
Be sure you understand how to deal with the toxic solutions you have, see the topic dealing with waste in the safety section...
Without seeing or knowing exactly what you have done or how, it can be hard to give answers to some of these questions, knowing if you dissolved gold into solution and that is where the black came from, or if you just have silver darkened by light, is hard for me to know from where I sit, with you asking about Harold's gold washing procedure it makes me think you believe you had gold in these powders...???
