Electrochemistry to much copper and lead with gold cell solution

[wood4lif]

a while back i ran a large amount of gold plated items (approx 40-50 lbs) through a reverse plating cell. looking back ive realized i ran my cell to hot for many long durations which gave me a very contaminated mixture of copper and led with my gold. i went ahead and ran through the process of hcl+cl for refining and ended up with a very disapointing yield. now i know there isnt much gold in most plated jewelry and such, but could i have run my contaminated powders through a nitric wash first after reverse plating with sulfuric acid prior to hcl+cl for possibly a better yield or was the damange already done with contamination due to long durations of excessive heat

 

[Lino1406]

Unfortunately, when gold content is low
it is not worth although possible
(on curiosity matters) to use medium strength
nitric

 

[steyr223]

Hi
I'm sorry for the interruption, but this has sparked
a question
I run my cell with very small stuff but notice
After about 12 thumb size chips in 2 quarts of sulfuric
acid the chips sizzle when washed
I then. Stop for a hour or so

If I am overheating and allowing the other metals to
be attacked then am I to understand this results is
Lower yeilds

Wouldn't there still be the same amount at Au with
just the added weight of the other metals
Or does the Au get trapped somehow
thanks Steyr223

 

[butcher]

Some metals are more reactive to sulfuric acid and will displace hydrogen from the acid as gas (metals above hydrogen in the reactivity series of metals), also high current can gas hydrogen from the electrolyte (or if water in solution hydrogen from the water splitting water creating hydroxides, (or oxygen gases depending on current), hydroxides and hydrogen gassing off, would lower solution acidity, also creating more base metal sulfates in solution.

If solution became loaded with base metals the resistance of cell may change to create more current and heating of the cell, gold soluble as a persulfate ion, but as these gold ions move from anode become diluted in the sulfuric acid no longer gold persulfate, the gold falls from solution, as gold is insoluble in sulfuric acid, so gold itself would not add that much to conductivity to the cells electrolyte like base metals can, these base metal ions can stay in acid solution loading the cell with conductive metal ions (of course some of the base metals will be reduced at cathode and fall into a sulfate sludge at bottom of cell other base metals would not plate out, and lower cells resistance to current.

The cells electrolyte water content is very important to help keep base metals from dissolving in solution, concentrated sulfuric acid can suck a lot of water from the air, especially cold air that holds a lot of water.

So even if we started with very concentrated acid we could be diluting our acids by the conditions we are using the cell.

Gold would still be there with base metals powders

 

[steyr223]

Thank-you
rob

 

[Geo]

too, like Harold explained, sulfuric acid is like two different acids. concentrated and diluted. each has different characteristics as diluted sulfuric will attack copper and concentrated sulfuric will not. if you are washing or rinsing parts in a container of water after stripping, each time you rinse a part, you are making a diluted sulfuric acid in your rinse container. when the concentration of acid becomes high enough it will start attacking the parts you are rinsing. when i strip pins, i always recycle my rinse water as it has both acid and gold powder in it. the rinse water always sizzles and fizzes before im done and is normally very contaminated with base metal. after the rinsing, i remove all the parts and let the powder settle.then i decant and evaporate down to the acid. the base metal will drop out because concentrated sulfuric will not hold the metal salts.the salts will fall out as green crystals.

 

[Madraykin]

Oh my! I actually understood that!