Lead or Lead oxide for collector metal?

[goldshark]

Just wondering if someone can explain when to use Lead, or Lead oxide for a collector metal. Lead oxide (PbO) is definitely a finer material for mixing into an intimate mixture with fluxes, so I see one advantage immediately. Jason with MBM and Milling, always uses a lump of metallic Lead (Pb) on top for the collector. I have never seen him use Litharge. I understand trying to oxidize certain components of the ores, Sulfides for instance. Can anyone tell me when one is advantageous over the other for reductions. Besides the fact that Lead is more readily available than (PbO), or Litharge.It seems a little confusing to use Litharge, which gets converted to metallic Lead, then back to Lead oxide in the cupellation furnace. If using Pb, does one need to add some nitrate to oxidize the sulfides, or Iron ? Can you over oxide by using PbO, nitrate, and nails? Am I over thinking it, or is this just the process I need to accept.

 

[orvi]

It has deeper reasons. One you just said - intimate mixing and micro lead globules forming, locked in the sintered mixture of flux and sample BEFORE it actually melts. This can greatly reduce smelting time to achieve comparable efficiency as with lead metal.
But PbO could also serve as flux, and it was used as component of it - you just don´t reduce all Pb. And many more things.

 

[snoman701]

The litharge acts as a solvent for metal oxides. Essentially, it not only helps contribute to redox relationship between Flour/Sugar:Litharge:metal being reduced to oxide, but also acts as a solvent (that happens to separate into the glass phase of the melt) to carry off the oxide into the slag.

Read Bugbee

 

[goldshark]

Thanks for the replies all. I did read Bugbee, and several other assaying handbooks, but didn't find any info on what the actual reactions are. Maybe I'll read it for a fourth time to see if I can glean a little more info that I missed. On another note, Jason with MBMM, should explain a little more in his videos about the differences in the 2 . I don't know if he participates in this forum, but if you do, maybe explain the relations of fluxes a little better. I am too busy, and lazy, to do a good assaying video. I don't see many recipes with Flourspar, which is a great thinner, in many recipes

 

[Ultrax]

If we talk about the direct collecting process in the crucible like Jason does (because there exist some other processes with litharge) usually metallurgists are using lead in metallic form.
You will receive the litharge as a result of lead oxidation during ore smelting. And yes, litharge can works as a solvent for metals oxides (except PM) and you will receive it in any case during the melting process in the oxidative atmosphere and it is an undesirable reaction in common (because of unproductive matte which increase the viscosity of the melt). I also recommend using a crucible with cover to minimize litharge quantity. So formally litharge is an undesirable sub-product (but still usable to recover lead again)
in our case, the only reason to use litharge instead of lead is a necessity to recover and use lead again.
You should add carbon powder to your crucible to be able to use litharge instead of metallic lead.
In the reaction between litharge and carbon lead will be reduced "in situ" and further process of smelting will be the same usual.
Another case is to use litharge when your ore already contains carbon particles and in this case, using litharge is more profitable.

 

[Ultrax]

P. S. Do not mix(!) smelting process with further cupellation. In the cupellation process, you should heat your button in an oxidative atmosphere to form a litharge which will oxidize all base metals and soak into the cupel.

 

[Dynoman]

If we talk about the direct collecting process in the crucible like Jason does (because there exist some other processes with litharge) usually metallurgists are using lead in metallic form.
You will receive the litharge as a result of lead oxidation during ore smelting. And yes, litharge can works as a solvent for metals oxides (except PM) and you will receive it in any case during the melting process in the oxidative atmosphere and it is an undesirable reaction in common (because of unproductive matte which increase the viscosity of the melt). I also recommend using a crucible with cover to minimize litharge quantity. So formally litharge is an undesirable sub-product (but still usable to recover lead again)
in our case, the only reason to use litharge instead of lead is a necessity to recover and use lead again.
You should add carbon powder to your crucible to be able to use litharge instead of metallic lead.
In the reaction between litharge and carbon lead will be reduced "in situ" and further process of smelting will be the same usual.
Another case is to use litharge when your ore already contains carbon particles and in this case, using litharge is more profitable.

Can you grind up the used Cupels & add these to the flux instead of Lead or Litharge?

 

[Ultrax]

Directly, usually not. Magnesium oxide from cupels is very difficult to melt (more than 2000°C). It will greatly interfere with the melt, forming a large mass of insoluble matte in which there will be a lot of precious metal in the form of drops. You can mix melted cupels with graphite powder and smelt lead from them at 900-1000 C, and then use the reduced lead as usual.

 

[Yggdrasil]

Directly, usually not. Magnesium oxide from cupels is very difficult to melt (more than 2000°C). It will greatly interfere with the melt, forming a large mass of insoluble matte in which there will be a lot of precious metal in the form of drops. You can mix ground fonts with graphite powder and smelt lead from them at 900-1000 C, and then use the reduced lead as usual.

Cupels are made mostly of bone ash, aren't they?
I think cupels are ground up and sifted for any stray prills of PM beads after end of life.
If I'm not mistaken, I think some also reclaim litharge from it, without remember how.

 

[Ultrax]

Most modern cupels (I mean industrial) are made from active magnesium oxide mixed with magnesium chloride.
Bone meal is now used in animal husbandry, but of course, you can make some DIY cupels using bone ash. But making ash from bones it is a very stink process

 

[Yggdrasil]

Most modern cupels (I mean industrial) are made from active magnesium oxide mixed with magnesium chloride.
Bone meal is now used in animal husbandry, but of course, you can make some DIY cupels using bone ash. But making ash from bones it is a very stink process

Hmm interesting.
What is active Magnesium Oxide?

 

[Ultrax]

Another name is: caustic calcined magnesia (CCM) is a highly reactive form of magnesium oxide produced by calcining or burning crude magnesite at relatively low temperature.

Different product Dead Burnt Magnesite is used for crucibles for melting steel.

 

[Yggdrasil]

Another name is: caustic calcined magnesia (CCM) is a highly reactive form of magnesium oxide produced by calcining or burning crude magnesite at relatively low temperature.

Different product Dead Burnt Magnesite is used for crucibles for melting steel.

So the CCM has high affinity for base metal oxides or any oxides then?

 

[Ultrax]

No. CCM has affinity to litharge with dissolved base metal oxides We use CCM for making large cupels (сan absorb over 500 grams of lead after its oxidation)

 

[Yggdrasil]

No. CCM has affinity to litharge with dissolved base metal oxides We use CCM for making large cupels (сan absorb over 500 grams of lead after its oxidation)

Thanks Ultrax
A good day today, because I learned something new

 

[Ultrax]

You're welcome

 

[snoman701]

In the US, cupels are available in both bone ash variety as well as magnesia variety.

You do not grind them up looking for prills, if you get visible prills you made a big mistake in your cupellation. The recovery of PM's from cupels is going to be based upon microscopic quantities that are drug off with the litharge as it is oxidized. Even then, it should be minimal. They are a hazmat item due to the lead oxide, and you pay to have them removed.

The recovery of PM's from these is best handled by someone with a large smelting operation. So you will simply crush, sift and assay so that you can sell as a prepared sweep.

 

[Yggdrasil]

In the US, cupels are available in both bone ash variety as well as magnesia variety.

You do not grind them up looking for prills, if you get visible prills you made a big mistake in your cupellation. The recovery of PM's from cupels is going to be based upon microscopic quantities that are drug off with the litharge as it is oxidized. Even then, it should be minimal. They are a hazmat item due to the lead oxide, and you pay to have them removed.

The recovery of PM's from these is best handled by someone with a large smelting operation. So you will simply crush, sift and assay so that you can sell as a prepared sweep.

Thanks for the clarification Snoman

 

[Ultrax]

In the US, cupels are available in both bone ash variety as well as magnesia variety.

Bone ash (formally Calcium hydroxyphosphate Ca5(OH)(PO4)3, which you can use as an equivalent replacement) was worse in our processes than active magnesium oxide (in quantitative litharge absorption meaning).

 

[goldshark]

Does anybody know of the optimal grinding size to gravitationally separate the Lead from the cupel materials, if this is even a viable option?