Boiling hydrochloric acid: Good and Bad

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Bertho
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Joined: April 8th, 2014, 9:48 pm
Country of Origin: USA

Boiling hydrochloric acid: Good and Bad

Post by Bertho » November 10th, 2019, 8:00 pm

I was solder leaching some through hole PCBs, with the components sheared off, in hot HCl as I have done before. I was using a crockpot but I had the setting set too high so when I checked it the HCl was boiling!
I turned it down to low setting. When I checked it about 12 hours later it was still boiling! The thermostat had failed which is why it was boiling in the first place. I cleaned out the crockpot and bought a new one.

Good:
A pleasant surprise: The almost impossible to remove solder resist on very old HP PCBs had peeled off.

Bad: Some gold was falling off the PCBs in pieces, some VERY small, and they are now mixed with the sludge, presumably consisting of lead chloride and tin chloride plus minor copper chloride and ???
There is no gold dissolved, I checked, and I can see the tiny gold pieces.

Questions: How to dissolve the Tin chloride? the Lead chloride? the sludge in general.
I have tried hot water and sulfuric acid with limited success.
Bertho

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