EXPERIMENTS ON CARBON AT HIGH TEMPERATURES
AND UNDER GREAT PRESSURES, AND IN CONTACT
WITH OTHER SUBSTANCES
From the Philosophical Magazine for September, 1893*
primary object of these experiments was to obtain a dense form of
carbon which should be more durable than the ordinary carbon when used
in arc lamps, and at the same time to obtain a material better suited
for the formation of the burners of incandescent lamps.
were a considerable number of experiments made in which the conditions
were somewhat alike, and many were almost repetitions with slightly
varying pressures and temperatures. They may, however, be divided into
two distinct classes: the first, in which a carbon rod surrounded by a
fluid under great pressure is electrically heated by passing a large
current through it; the second, in which the liquid is replaced by
various substances such as alumina, silica, lime, etc.
arrangement of the experiment was as follows: A massive cylindrical
steel mould of about 3 inches internal diameter and 6 inches high was
placed under an hydraulic press; the bottom of the mould was closed by
a spigot and asbestos-rubber packing similar to the gas check in guns;
the top was closed by a plunger similarly packed; this packing was
perfectly tight at all pressures. In the spigot was a centrally bored
hole into which the bottom end of the carbon rod to be treated fitted;
the top end of the carbon rod was connected electrically to the mould
by a copper cap which also helped to support the carbon rod in a
central position. The bottom block and spigot were insulated
electrically from the mould by asbestos, and the leading wires from the
dynamo being connected to the block and mould respectively, the current
passed along the carbon rod in the interior of the mould.
fluid was run in so as to cover the rod completely. The plunger was
then free to exert its pressure on the liquid without injuring the
carbon. The pressure in the mould was indicated by the gauge on the
Experiments. Class I
Among the liquids tested were benzene, paraffin, treacle, chloride and bisulphide of carbon.
The pressures in the mould during the several experiments were main-
* From the Proceedings of the Royal Society, Vol. xliv. Communicated, with an additional note on Diamond Manufacture, by the Author.