To P. Budd:
Many thanks for your reply. I can easily see how a co-smelt can operate and
also see how a Sn mineral (either stannite or cassiterite) could be reduced
above a Cu bath with the use of a layer (even a thin one) of charcoal. What
puzzles me is that if what McDonnell writes that up to 30% Sn ended up in the
Cu in experiments done by one of his students in which cassiterite was added
to molten Cu, then what is wrong with the thermodynamics or at least the
calculations based upon the Ellingham plots of the oxidation/reduction curves
for CuO and SnO! For example, are their curves in error? Is the separation of
the two curves (really straight lines) sufficiently apart to 'permit' as much
as 30% Sn to be reduced and go into solution? Such a possible suggestion was
made recently to me by Michael McNeil in that the Woods/Garrels
redetermination of these oxidation/reduction lines might permit such a result.
R. Maddin
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