have taken pieces of platinum-foil, tinfoil, and lead-foil, and rolled
them together; and if I apply the blowpipe to them, you will have, in
fact, a repetition on a larger scale of the experiment you saw just now
when the lead and platinum came together, and one spoiled the other. When
the metals are laid one upon the other, and folded together and heat
applied, you will not only see that the platinum runs to waste, but that
at the time when the platinum and lead are combined there is ignition
produced there is a power of sustaining combustion. I have taken a large
piece, that you may see the phenomenon on a large scale. You saw the
ignition and the explosion which followed, of which we have here the
results the consequence of the chemical affinity between the platinum and
the metals combined with it, which is the thing upon which Deville founds
his first result.
When he has melted these substances and stirred them well up, and so
obtained a complete mixture, he throws in air upon the surface to burn off
all the sulphur from the remaining sulphuret of lead; and at last he gets
an ingot of lead with platinum much lead, comparatively, and little
platinum. He gets that in the crucible with a lot of scori and other
things, which he treats afterwards. It is that platiniferous lead which we
have to deal with in our future process. Now, let me tell you what he does
with it. His first object is to get rid of the lead. He has thrown out all
the iron, and a number of other things, and he has got this kind of
compound indicated in the table. He may get it as high as 78 per cent. of
platinum, and 22 of lead; or 5, or 10, or 15 of platinum, and 95, or 90,
or 85 of lead (which he calls weak platinum), and he then places it in the
kind of vessel that you see before you. Suppose we had the mixture here;
we should have to make it hot, and then throw in air upon the surface. The
combustible metal that is, the lead and the part that will oxidise, are
thoroughly oxidised; the litharge would flow out in a fused state into a
vessel placed to receive it, and the platinum remains behind.
[Illustration: Fig. 36.]
Here is the process which Deville adopts for the purpose of casting off
the lead, after he has got out the platinum from the ore. (Having made use
of your friend, you get rid of him as quickly as you can.) He gets his
heat by applying the combination of oxygen and hydrogen, or of carburetted
fuel, for the purpose of producing a fire. I have here a source of
coal-gas; there I have a source of hydrogen; and here I have a source of
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