Odd crystals in my auric cloride

[rickbb]

Finished up a batch of fingers in AP and had them dissolved nicely in HCL/CL.

Put it on some low heat, (160F), to drive out the excess CL when I thought that I just could reduce the volume of liquid to deal with so I left it on the heat to evaporate the water off and concentrate the AU.

After reducing to about half the original volume, turned off the heat and let cool to room temp. Came back after a few hours and I have these square crystals in the bottom. They are about 1/8 inch square.

Stirring seems to try and dissolve them a bit, but appears to just make smaller crystals.

Question is, what are they, some containment that got in? I had mostly clean foils with the usual bits of green mask. But there must have been some other material in there as well.

I'm guessing I can let it settle out and filter it out.

 

[g_axelsson]

Looks like sodium chloride, it is cubic and forms square crystals. Add some water and dissolve it.
You want to add water anyhow to precipitate silver chloride.

Göran

 

[Geo]

It looks like sodium chloride left over from the bleach. It will dissolve in water.

 

[Palladium]

What he said!

 

[butcher]

These are chloride salts, the bleach is basic and it will make more salts of your HCL acid,
normally these salts will not show up in your solution, as the acid and bleach contains a lot of water, but when you heated you evaporated the water needed to keep these salts soluble, which upon concentration or lack of water will form insoluble salts, mostly sodium chloride, some sodium chlorate, the longer needle like crystals in the picture makes me believe you have some lead chloride in your solution.

 

[rickbb]

Thanks, I totally did not think of the bleach leaving the salts behind after the free CL was used up. I added water to bring it back to the original volume and all the larger crystals are gone. Just a few granular white stuff settled in the bottom.

That may well be lead as there were some depopulated cell/PCB boards in this batch. I need to work on better soaking and rinsing procedures before going to digesting.

I had been saving up all my auric chloride to drop the AU in one batch and thought I could reduce my volume of liquid this way. I suppose I will need to invest in some larger containers instead.

 

[Geo]

Sodium chloride, once formed, will stay in solution and will not evaporate off. As the solution condenses, crystals form. You can re-hydrate and evaporate to completely dry over and over and the salt stays the same. You can break the bonds of the sodium chloride but if I'm not mistaken, it takes more energy to break the bonds than energy gained.