Video discussion. Gold recovery from 14kg of CPU by using the lead bath method.

[Yggdrasil]

I did lead cupellation many many times and make a lot of calculations then compared results with fire assay and with acids method, lead cupellation method is ok only if you use it with very small materials such as fire assay, so you use electric furnace and cupellation not take long time.

But with large quantities that you use direct or even indirect flame with it and took long time, lead cupellation method will not give you more than 90% of gold and about 80% silver, and am not sure about rest PM's. At least from my experience, but what make me sure about that is that big boys who make cupellation always get values from the powder caught into their filter bags.

Did you see Owltech's video?
He dissolves the values quite fast and complete in molten Lead.
To get the values out he does a hybrid cupeling on a sheet of stainless.
Then he part it in Nitric.

But I think that if you have sufficient material you could use the Parkes process.

 

[Ayham Hafez]

Do you have some more info about that? Does 10% of the gold go up in the fumes or in the cupel?

Usually gold and silver missing in cupellation process comes in two forms, very fine particles that evaporated which can be collected in the filter bags if you use it, or with lead oxide absorbed by the bone ash or whatever material you use.

I have a friend told me that they got gold in their filter bags after finishing cupellation they usually process filter bags material after tens of cupellation processing, and from my experience I got gold and silver from lead oxide absorbed by the cupellation material (usually I use Portland cement)

 

[Ayham Hafez]

Did you see Owltech's video?
He dissolves the values quite fast and complete in molten Lead.
To get the values out he does a hybrid cupeling on a sheet of stainless.
Then he part it in Nitric.

But I think that if you have sufficient material you could use the Parkes process.

I tested parkes process before using zinc and aluminum, I got only 40% of the gold, I think it's not a good process to use with gold, but with silver I think it's OK if you process ore like Galina.

I did cupellation many many times, make mistakes and learnt, lead cupellation method is the fastest method to recover PM's but you will not reach to the highest recovery rate because lead evaporate very quickly carrying with it some PM's, also oxidized very quickly which make some PM's stuck to the oxidized lead so they will not be part of the melted dore.