Professor
Mitinsky states that the results were very good, and adds that by this
method tools can be obtained that can be run safely at a rim speed of
25 meters per second.
Diamond-carbon in meteorites.—Following
up his researches on the Canyon Diablo meteorite, Prof. Henri Moissan
has published a more extended article describing those researches in
fuller detail and also certain conclusions thence derived, together
with new experiments as to diamond production." Tlie results shown are
(1) that it is only in certain specimens of this meteorite that carbon
appears at all; (2) that in some pieces it is present in several forms,
as amorphous carbon in two or three distinct varieties, as graphite,
and as diamond in two varieties, black and transparent; (3) that these
latter are found inclosed in or surrounded by a zone of amorphous
carbon and in small fissures which stand in close relation to nodules
of troilite and other compounds containing phosphorus and silicon in
addition to the sulphur. Microscopic examination shows that even the
portions of the iron that appear homogeneous frequently contain small
nodules of this character. I'rofessor Moissan judged, from various
studies by himself and others, that the metalloids—silicon, phosphorus,
and sulphur—all tend to displace the carbon from molten iron, and that
an increase in the proportion of nickel, which is found to vary
considerably in different parts of the meteorite, lessens the
solubility of carbon in tlie alloy as compared with pure iron. These
two conditions, therefore, should cooperate to favor the separation of
carbon in such a meteorite, as compared with Professor Moissan's former
process of diamond production in the electric furnace.
These
suggestions led him to undertake a series of new experiments to test
the effect of conditions thus modified. These are described in much
detail, with the general result that the addition of small quantities
of monosulphide of iron, or of silicon, to the crucible of melted iron
with carbon, on its removal from the electric furnace and just before
its immersion in cold water, appeared to facilitate the production of
minute diamonds similar to those of bis former experiments, but in
larger number and with slight crystnllographic differences. The
addition of a small percentage of nickel, on the other hand, produced
no apparent change from the results with pure iron. The introduction of
phosphate of iron not only failed to increase the quantity of diamonds
but apparently lessened it. Professor Moissan therefore concluded that
the diamond carbon in the Canyon Diablo meteorite has probably been set
free from an iron carbide by the action of sulphur, and to some extent
of silicon, the latter having also partly united with the carlion to
form the silicon carbide
which the found in association and which the writer named Moissanite,
the natural form of the artificial product carborundum.
The crystallographic features of the
microscopic diamonds are described, and the very interesting fact is
noted that in a number of instances the little crystals broke
spontaneously days or even weeks after their formation, tints
presenting a striking parallel to the occasional behavior of diamonds
from the blue ground of South Africa.
Considerable
space is given to experiment and discussion as to the action of melted
iron in solidifying in respect to expansion or contraction. The fact
seems clearly shown that pure iron follows the ordinary law, but that
iron with dissolved carbon expands in passing to the solid state,
producing when confined the enormous pressure which causes the carbon,
or some part of it. to crystallize as diamond, instead of all assuming
the amorphous or tlie graphitic form.
Artificial production of diamonds.—Two processes have been announced by German experimenters whereby it is claimed that minute crystals of diamonds
" Nouvelles
recherches sur in reproduction du diamant, par Henri Moissan : Ann. de
chimie ot de phys., 8ta ser., vol. 5. June. tan,".
