to make a few small splinters of Diamond to here give Moissan's method from Sir W. Crookes' paper on "Diamonds,"1 by that author's kind permission:—
"For
the manufacture of—I am afraid I must say an infinitesimal—diamond, the
first necessity is to select pure iron—free from sulphur, silicon,
phosphorus, etc.,—and to pack it in a carbon crucible with pure
charcoal from sugar. The crucible is then put into the body of the
electric furnace, and a powerful arc formed close above it between
carbon poles, utilising a current of 700 amperes at 40 volts pressure.
The iron rapidly melts and saturates itself with carbon. After a few
minutes' heating to a temperature above 4,000° C —a temperature at
which the iron melts like wax and volatilises in clouds—the current is
stopped, and the dazzling fiery crucible is plunged beneath the
surface of cold water, where it is held till it sinks below a red
heat. As is well known, iron increases in volume at the moment of
passing from the liquid to the solid state. The sudden cooling
solidifies the outer layer of iron and holds the inner molten mass in a
tight grip. The expansion of the inner liquid on solidifying produces
an enormous pressure, and under the stress of this pressure the
dissolved carbon separates out in transparent forms—minutely
microscopic, it is true—all the same veritable diamonds, with
crystalline form and appearance, colour, hardness, and action on light
the same as the natural gem.
" Now commences the tedious part of the process. The
1
"Diamonds." A lecture delivered before the British Association at
Kimberley, September 15, 1905, by Sir William Crookes. Published at the
Chemical Neivs Office, 16, Newcastle Street, Parringdon Street, London. Price Is.
G 2
