The furnace used by Henri Moissan in his experiments on reactions at high temperatures, on the fusion and volatilization of refractory materials, and on the formation of carbides, suicides and borides of various metals, consisted, in its simplest form, of two superposed blocks of lime or of limestone with a central cavity cut in the lower block, and with a corresponding but much shallower inverted cavity in the upper block, which thus formed the lid of the furnace.
Moissan showed that at this temperature the most stable of mineral combinations are dissociated, and the most refractory elements are converted into vapour, only certain borides, silicides and metallic carbides having been found to resist the action of the heat.
Wirthwein, the titanium mineral is fused with carbon in the electric furnace, the carbides treated with chlorine, and the titanium chloride condensed.
The graphite veins in the older crystalline rocks are probably akin to metalliferous veins and the material derived from deep-seated sources; the decomposition of metallic carbides by water and the reduction of hydrocarbon vapours have been suggested as possible modes of origin.
Moissan has also shown that it will combine with many metals at the temperature of the electric furnace, to form carbides (q.v.).
Carbides of chromium are known; when the metal is heated in an electric furnace with excess of carbon, crystalline, C2Cr 3, is formed; this scratches quartz and topaz, and the crystals are very resistant to the action of acids; CCr 4 has also been described (H.
In connexion with these experiments he developed the electric furnace as a convenient means of obtaining very high temperatures in the laboratory; and by its aid he prepared many new compounds, especially carbides, silicides and borides, and melted and volatilized substances which had previously been regarded as infusible.