Vanadium Carbide, VC

Vanadium Carbide, VC, forms silvery-white crystals which are harder than quartz; density 5.25 to 5.40; m.pt. approximately 2750° C. Vanadium carbide is not attacked by water, hydrochloric acid, or hydrogen sulphide, even at a red heat. Nitric acid dissolves it in the cold. It burns at 800° C. in chlorine with incandescence, and at a red heat it reacts with oxygen, nitrogen, ammonia, potassium nitrate, and potassium chlorate. On being fused with vanadium trioxide, V₂O₃, in a crucible provided with a refractory lining, the carbon burns away and a product containing 98.11 per cent, of vanadium is obtained. The dissociation pressures, electrical conductivity, and crystal structure for this carbide have been measured.

Moissan reported the existence of several other vanadium carbides, V₃C, V₃C₂, V₂C₂, V₂C₃, and some of these have received attention in connection with the investigation of the constitution of vanadium steels. Arnold and Reed isolated a double carbide of iron and vanadium having the formula 2Fe₃C.V₄C₃, but V₄C₃ may be a mixture of several other carbides. The action of various etching agents on vanadium carbide has been investigated with a view to distinguishing it from other carbides in metallographic work.

A carbide of vanadium is also obtained by the action of carbon monoxide on the metal at 500° to 800° C. The finely divided metal catalyses the reaction, 2CO = CO₂ + C, and the carbon thereby isolated is taken up by the vanadium.