Niobium Trichloride, NbCl₃

Niobium Trichloride, NbCl₃, is prepared by leading the vapour of niobium pentachloride through a heated tube. It is also formed in small quantity by the action of carbon tetrachloride vapour on niobium pentoxide contained in a hard-glass tube, and has probably been prepared in solution by the electrolytic reduction of the pentachloride. It forms a black, crystalline crust with an almost metallic lustre, which closely resembles the appearance of a film of sublimed iodine. It is not decomposed by water or ammonia, but is readily oxidised by dilute nitric acid to niobium pentoxide. On being heated to a red heat in an atmosphere of carbon dioxide, a sublimate of niobium oxytrichloride, NbOCl₃, is produced, the carbon dioxide undergoing reduction to the monoxide.