THE BOOK OF DIAMONDS
the
carbon at the temperature of the electric furnace the crucible
containing the fused metal was removed from the furnace and plunged
into ice cold water. The pressure produced by the quick chilling of
the outer crust with, an internal expansion changed the black sugar
carbon to crystal diamonds. The iron of the solidified mass was
dissolved in strong acids. From this residue Moissan obtained tiny
crystals which had the properties of diamonds. His largest synthetic
diamonds were three-fourths of a millimeter in diameter.
In
a paper to the Royal Society in 1888 Hon. Sir Charles Parsons described
experiments in which a carbon rod heated by a current of electricity
was immersed in liquids at pressures up to 2,200 atmospheres, and in
which the liquids-benzene, paraffin, and bisulfide of carbon—were found
to yield deposits of amorphous carbon.
In
another paper to the Royal Society in 1934 he gave the following
method. A deep iron dish was packed tightly with graphite, and above
the graphite was filled in loosely to a depth of half an inch covering
the ingot of iron. An arc was struck by a carbon on to the ingot
submerged in the loose graphite. When the iron was well boiled the
ingot remained in the bed until it had quite set, hard enough to handle
with the iron spoon, and then cooled in water and mercury. It gave a
fair diamond residue. About one to three per cent of other elements
such as manganese, cobalt, and silicon added to iron appeared to give
the best results.
It has been long known that iron, when melted, dis-
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