| Dichromium Silicide, Cr2Si, has been prepared in the form of lozenge-shaped crystals with brilliant facets, by causing silicon in increasing proportions to act upon chromium dissolved in copper. Moissan obtained it as small prismatic crystals by heating chromium in a dish lined with silicon at a temperature rather above 1200° C. in a current of hydrogen; by heating pure chromium with 15 per cent, of its weight of silicon in a carbon crucible in an electric furnace; and by heating a mixture of 6 parts of silica, 20 parts of chromium sesquioxide, and 7 parts of sugar carbon in the electric furnace. The product, which always contained some carbide, was washed with cold concentrated hydrofluoric acid. The crystals are hard enough to scratch quartz and even corundum. The silicide is attacked at red heat by chlorine with incandescence; hydrogen chloride at 700° C. gives the chlorides of silicon and chromium; fused potash slowly attacks it. |