# dropping lead/tin



## edsikes (Sep 17, 2014)

ok so im seeing lots of posts about dropping lead and tin using sulfuric, but what concentration of sulfuric? and how much is enough? 3 or 4 drops? because thats what it seems like they use in the videos but im just not sure


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## solar_plasma (Sep 17, 2014)

What you want to learn is called stoichiometry (http://en.wikipedia.org/wiki/Stoichiometry)

PbCl2 + H2SO4 -> PbSO4 + 2HCl

So, one mol sulfuric will drop one mol lead. Or, 98,08g sulfuric (if it would be 100%, so you need to calculate, how much there is in your dilluted solution) will drop 207,2g lead or 278,1g PbCl2.

Dropping tin with sulfuric will not work in my understanding.


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## butcher (Sep 17, 2014)

Most of the time we can normally eliminate much of the lead from our scrap with mechanical separation or pretreatment.

Another method we can use as a pretreatment is to remove lead by attacking the lead solder (lead/tin solder) with HCl without an oxidizer so that the tin goes into solution, breaking down the finely divided lead enough, to oxidize it into an insoluble lead chloride powder. Leaving the more unreactive metals intact, (metals like copper and gold that are below hydrogen in the reactivity series), that will not dissolve without the oxidizer added to the HCl acid),

Copper II chloride used as a leach will also dissolve tin and copper into solution, and break down lead to an insoluble lead chloride powder, but will not dissolve much of the gold, if you do not add too much oxidizer, what fine gold that does get attacked will end up as fine black powder mixed in with the insoluble materials like the lead chloride.

Lead chloride is pretty insoluble in cold water (or solutions), but can become pretty soluble in hot water, here is another tool we use to remove lead chloride from our material.


When we are working with an acidic chloride solution, like HCl (with an oxidizer) or aqua regia, most of the lead will become an insoluble lead chloride which if it is left to settle can be removed by careful decanting of the solution and filtering, what lead does carry through the process with this solution can then be removed with a few drops of sulfuric acid, and precipitated out of solution as a lead sulfate.

Normally by this stage you do not have much lead left in solution to remove (if you done your work well in previous steps), so it does not take much sulfuric acid to remove the lead from solution.


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## phillips2316 (Sep 20, 2014)

my tin will not dissolve in HCL...Help


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## Claudie (Sep 20, 2014)

phillips2316 said:


> my tin will not dissolve in HCL...Help



Did you try heating it?
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=41&t=5271&p=45030#p45030


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## galenrog (Sep 20, 2014)

What is the source of your tin? Also, what is the source of your HCL?


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## butcher (Sep 20, 2014)

I normally hammer the tin flat and cut it to small strips or chips or scrapings, with a pocket knife, and twist the strips to make it dissolve easier in the warmed HCl acid.

If the chunk of tin was large you might not be able to tell if much of it dissolved into solution.

Stannous chloride is a clear solution so if tin is dissolving into the acid you may not see it very well, A gold standard solution will tell you if you have tin in solution.

As others have asked are you sure what you have is tin, and HCl and what is their source?


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