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PRECIOUS STONES.
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and
Dana, many agreeing and many disagreeing. Damour and Gannal, of Brazil,
considered that the Diamond might be due to the reduction of carbon
bi-sulphide (an evil smelling impurity of coal gas). A. Favre, and
later the Hon. St. Claire Deville, were led by a study of the minerals
associated with the Diamonds of Brazil to consider their formation the
result of the reduction of fluorine or chlorine compounds of carbon.
Whether this may be the true origin of Brazilian Diamonds or not, it is
the writer's opinion that if successful experiments are undertaken in
the laboratory it will be in the reduction of such carbon compounds.
Perhaps
one of the first experiments on the artificial production of Diamonds
to meet with any success was carried out by Despritz in 1853. The
method employed by him was to pass the electric spark in vacuo for a
month, using a platinum rod as one terminal and a carbon cylinder as
the other. The platinum terminal was found to be encrusted with minute
octahedral crystals which answered all the tests applicable to the
Diamond.
In 1880 J. B. Hannay,1
of Glasgow, carried out no less than eighty experiments upon the
reduction of a carbon compound, only three of which were successful.
Iron tubes 20 inches long by 1 inch thick and 1/2 inch bore were
filled about two-thirds full of pure paraffin spirit with a little
charcoal, and then sealed off. The sealing of these tubes was the most
difficult part of the undertaking. In the earlier experiments screw
stoppers, luted in with a mixture of silicate of soda and manganese
dioxide, were used, but
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