The _carbide_, TiC, was prepared by Moissan by heating the oxide with carbon in the electric furnace; any excess of carbon separates on cooling as graphite. It has the density 4·25, and resembles the fused element in appearance. It dissolves in nitric but not in hydrochloric acid. _Titanium tetrafluoride_, TiF₄, is obtained by the action of fluorine on the element or the carbide, and by the action of anhydrous hydrofluoric acid on the element or the tetrachloride. It is a white powder, and boils at 284°; it is very hygroscopic, and dissolves easily in alcohol and water, showing little tendency to form basic salts. From the concentrated aqueous solution it separates as the dihydrate, TiF₄,2H₂O; basic salts are obtained only by repeated evaporation with water. The anhydrous compound forms additive products with ammonia and with pyridine. With aqueous hydrofluoric acid it forms the complex H₂TiF₆, as shown by conductivity measurements, and the fact that only a slow and incomplete precipitation of the hydroxide is effected by addition of ammonia. The solution dissolves metallic oxides and carbonates, forming _titanofluorides_, which are for the most part isomorphous with the corresponding silicofluorides, stannofluorides, and zirconofluorides. They are very stable crystalline salts, of the general formula R´₂TiF₆; many salts of the types R´´TiF₆, R´₃TiF₇, etc., have been prepared. The most important is the potassium salt, K₂TiF₆, which crystallises from acid solutions in monoclinic tablets; from aqueous solution it separates as the monohydrate, K₂TiF₆,H₂O, isomorphous with the compounds K₂CbOF₅,H₂O and K₂WO₂F₄,H₂O. The hydrate loses its water at 100°, and melts at a white heat without decomposition. It is moderately soluble in hot, very sparingly soluble in cold water, and hence is readily recrystallised. The _tetrachloride_, TiCl₄, is important, on account of its low boiling-point, for the separation and purification of titanium compounds. In physical as well as chemical properties, it resembles the chloride of a non-metallic element rather than a normal salt, and is distinguished by the ease with which it combines or reacts with the most widely differing organic compounds. It is prepared by the action of chlorine upon the element, the carbide, or a mixture of the dioxide with carbon, and by the action of chloroform or carbon tetrachloride upon the dioxide at a bright red heat. It is a colourless, transparent liquid, of density 1·76 at 0°; it freezes at -23°, and boils at 136° under atmospheric pressure. In moist air it fumes excessively, yielding hydrogen chloride by hydrolysis: TiCl₄ + H₂O = TiOCl₂ + 2HCl, and is decomposed by water with separation of the hydrated oxide. If the compound be added slowly to a large quantity of cold water, and the clear solution warmed, the oxide formed by hydrolysis remains in colloidal solution.