Ignatz61 said:
So, what is the reason for the lead cathode?
I'm not sure I can answer that question, having never operated one of the cells, but I get the idea it is used because of its resistance to sulfuric acid. That need not be the case, assuming the acid is concentrated. Our very own GSP, who has considerable experience running sulfuric cells, claims that mild steel (low carbon steel) is quite resistant to dissolution in concentrated sulfuric, so stainless need not be used. It's important that water not be introduced to the cell, otherwise items that might not dissolve readily, will. I know that's true of cast iron, which is quite resistant to concentrated sulfuric, but can't withstand it when dilute.
I made mention of witnessing a large stripping cell in operation. They used baskets made of copper. For very small items, copper window screen would work quite well, and I believe Lazersteve has some for sale on his web site. For larger items, a copper basket can be fashioned from coarse copper screen. You might consider exploring something like ¼" mesh, which would have a much heavier wire in its construction than the finer screen materials. You would benefit from the heavier wire in longevity and rigidity of the basket. The basket is suspended by a pair of arms, made of copper buss bar, which become the electrical path to the basket.
Is it because it is unaffected by the acid? If that is the case then could we use a lead bag or perforated container as the Anode so to speak?
Could be a basket made of lead would work adequately, but lead is not known for its strength, and would easily deform. Could be a problem, depending on size and application. In this instance I'm speaking from the perspective of a machinist, not a refiner. I think lead, in larger sizes, would be an ongoing problem.
lastly, And I have asked this a couple of times in various posts-How do I know when it is time to filter the acid?
Thanks again,
JOhn
Again, without a working knowledge of cells, I may be way off course, but one indication is when amperage won't fall below acceptable limits. I would expect that when there's too much gold in suspension, the cell will conduct, even when it isn't removing any gold from the surface of parts. As I was instructed by those that operated the cell I witnessed, voltage was raised to a maximum of 28 volts before parts were removed from their cell. When amperage dropped, they considered that they had stripped all of the gold that was accessible. To give you an idea of the magnitude of this operation, they had stripped something like $35,000 worth of gold, and that is back in '75, when gold was roughly $100/ounce. The yard was filled with 55 gallon drums of copper based alloy materials that had been stripped. A rare example of government doing the right thing, the right way.
Harold