we
may so fully depend upon the properties of the various substances we have
to deal with; that we can, by carrying out our processes, obtain a
material like this, allowing of division and extension under a rolling
mill--a material of the finest possible kind, the parts being held
together, not with interstices, not with porosity, but so continuous that
no fluids can pass between them; and, as Dr. Wollaston beautifully shewed,
a globule of platinum fused by the voltaic battery and the oxy-hydrogen
blowpipe, when drawn into a wire, was not sounder or stronger than this
wire made by the curious coalescence of the particles by the sticking
power that they had at high temperatures. This is the process adopted by
Messrs. Johnson and Matthey, to whose great kindness I am indebted for
these ingots and for the valuable assistance I have received in the
illustrations.

The treatment, however, that I have to bring before you is of another
kind; and it is in the hope that we shall be able before long to have such
a thing as the manufacture of platinum of this kind, that I am encouraged
to come before you, and tell you how far Deville has gone in the matter,
and to give you illustrations of the principles on which he proceeds. I
think it is but fair that you should see an experiment shewing you the way
in which we get the adhesion of platinum. Probably you all know of the
welding of iron: you go into the smith's shop, and you see him put the
handle of a poker on to the stem, and by a little management and the
application of heat he makes them one. You have no doubt seen him put the
iron into the fire and sprinkle a little sand upon it. He does not know
the philosophy he calls into play when he sprinkles a little sand over the
oxide of iron, but he has a fine philosophy there, or practises it, when
he gets his welding. I can shew you here this beautiful circumstance of
the sticking together of the particles up to the fullest possible
intensity of their combination. If you were to go into the workshops of
Mr. Matthey, and see them hammering and welding away, you would see the
value of the experiment I am about to shew you. I have here some
platinum-wire. This is a metal which resists the action of acids, resists
oxidation by heat, and change of any sort; and which, therefore, I may
heat in the atmosphere without any flux. I bend the wire so as to make the
ends cross: these I make hot by means of the blowpipe, and then, by giving
them a tap with a hammer, I shall make them into one piece. Now that the
pieces are united, I shall have great difficulty in pulling them apart,
though they are joined only at the point where the two cylindrical
surfaces came together. And now I have succeeded in pulling the wire
apart, the division is not at the point of welding, but where the force of
the pincers has cut it, so that the junction we have effected is a
complete one. This, then, is the principle of the manufacture and
production of platinum in the old way.

The treatment which Deville proposes to carry out, and which he has
carried out to a rather large extent in reference to the Russian supply of
platinum, is one altogether by heat, having little or no reference to the
use of acids. That you may know what the problem is, look at this table,
which gives you the composition of such a piece of platinum ore as I
shewed you just now. Wherever it comes from, the composition is as
complicated, though the proportions vary:--

Platinum, . . . . . 76.4
Iridium,. . . . . . 4.3
Rhodium,. . . . . . 0.3
Palladium,. . . . . 1.4
Gold, . . . . . . . 0.4
Copper, . . . . . . 4.1
Iron, . . . . . . . 11.7
Osmide of Iridium,. 0.5
Sand, . . . . . . . 1.4
-----
100.5

This refers to the Uralian ore. In that state of combination, as shewn in
the table, the iridium and osmium are found combined in crystals,
sometimes to the amount of 0.5 per cent., and sometimes