you have three
precious metals (for you may call platinum a precious metal) worked into
coin, they will be sure to run counter to one another. Indeed, the case
did happen, that the price of platinum coin fixed by the Government was
such, that it was worth while to purchase platinum in other countries, and
make coin of it, and then take it into that country and circulate it. The
result was, that the Russian Government stopped the issue. The composition
of this coin is--platinum, 97.0; iridium, 1.2; rhodium, 0.5; palladium,
0.25; a little copper, and a little iron. It is, in fact, bad platinum: it
scales, and it has an unfitness for commercial use and in the laboratory,
which the other well-purified platinum has not. It wants working over
again.

Now, Deville's process depends upon three points,--upon intense heat,
blowpipe action, and the volatility of certain metals. We know that there
are plenty of metals that are volatile; but this, I think, is the first
time that it has been proposed to use the volatility of certain
metals--such as gold and palladium--for the purpose of driving them off
and leaving something else behind. He counts largely upon the volatility
of metals which we have not been in the habit of considering volatile, but
which we have rather looked upon as fixed; and I must endeavour to
illustrate these three points by a few experiments. Perhaps I can best
show you what is required in the process of heating platinum by using that
source of heat which we have here, and which seems to be almost
illimitable--namely, the voltaic battery; for it is only in consequence of
the heat that the voltaic battery affects the platinum. By applying the
two extremities of the battery to this piece of platinum-wire, you will
see what result we shall obtain. You perceive that we can take about this
heating agent wherever we like, and deal with it as we please, limiting it
in any way. I am obliged to deal carefully with it; but even that
circumstance will have an interest for you in watching the experiment.
Contact is now made. The electric current, when compressed into thin
conducting-wires offering resistance, evolves heat to a large extent; and
this is the power by which we work. You see the intense glow immediately
imparted to the wire; and if I applied the heat continuously, the effect
of the current would be to melt the wire. As soon as the contact is
broken, the wire resumes its former appearance; and now that we make