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THE BOOK OF DIAMONDS
was
confident that he could build a furnace of the required type. Special
steels were generously contributed by steel companies and after a great
deal of work and research, the furnace was completed—a simple affair no
larger than a two-gallon pail, but capable of producing temperatures
exceeding 4,000 degrees, Centigrade.
Crucibles
and electrodes of chemically pure synthetic graphite were made by the
Acheson Graphite Company at Niagara Falls for use in the furnace. It
was necessary to install a special transformer and a heavy power line,
since the power consumption of the electric furnace was extremely high.
On
June 7, 1929, a mixture of two parts of chemically pure iron filings
and one part of pure sugar carbon, parts taken by volume, was placed in
a graphite crucible, which in turn was placed in the furnace and heated
continuously for one hour and seven minutes, after which, the crucible
was removed and plunged into freezing mixture.
As
the white hot molten iron cooled to a red solid, it expanded. As it
cooled from a red solid to room temperature, it contracted. Thus the
outside surface of the iron, which cools more rapidly than the inside
of the mass, contracted while the inside still expanded. The carbon
which dissolved in the iron was thus subjected to a pressure estimated
at 180,000 pounds, or ninety tons, per square inch.
The
hardened mass of carbon and iron was removed from the freezing mixture
and treated with hot aqua regia for 300 hours to dissolve the iron. The
residue, mostly amorphous carbon and graphite, was digested as much as
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