TITANIUM. 607 



its properties. The composition assigned to it above is, therefore, 

 hypothetical. 



Titanic acid, TiO 2 , 503.7 or 40.33. In the mineral rutile, 

 titanic acid is crystallized in the form of tin stone ; the link by 

 which tin is connected with titanium. Again ilmenite and 

 other varieties of titanate of iron, FeO, TiO 2 , are isomorphous 

 with peroxide of iron, (page 146) ; and thus tin comes to be con- 

 nected through titanium with the last order of metals. But ti- 

 tanic acid is dimorphous, and crystallizes, in anatase, in an un- 

 connected form. Titanic acid is procured more easily from the 

 titanate of iron, reduced to powder and levigated, which is fused 

 with sulphur. The sulphur has no action upon the titanic acid, 

 but converts the protoxide of iron into a sulphuret of iron, 

 which is dissolved by hydrochloric acid. If iron is still retained 

 by the titanic acid, the latter is heated in a stream of sulphu- 

 retted hydrogen gas, by which every particle of iron is con - 

 verted into sulphuret, and then removed by hydrochloric 

 acid. 



Titanic acid is a white powder, which acquires a yellow tint 

 by a high temperature ; it is infusible and insoluble in water. 

 Titanic acid is considerably analogous in properties to silica; 

 like that acid it has a soluble modification, formed by igniting 

 titanic acid with an alkaline carbonate, which is soluble in dilute 

 hydrochloric acid. The acid solution of titanic acid gives an 

 orange-red precipitate with an infusion of gall-nuts, which is 

 characteristic of titanic acid. On neutralising the acid solution 

 with ammonia, the soluble modification of titanic acid is thrown 

 down as a white gelatinous precipitate. When this precipitate 

 is dried and heated, it glows, and the titanic acid is no longer 

 soluble in acids. When a solution of bichloride of titanium, or 

 of the sulphate of titanic acid in water, is boiled for some time, 

 titanic acid precipitates in the insoluble modification. 



Bisulphuret of titanium, Ti S 2 , was discovered by Rose, who 

 formed it by passing the vapour of the bisulphuret of carbon 

 over titanic acid, in a porcelain tube maintained at a bright red 

 heat. 



Bichloride of titanium, Ti C1 2 , was formed by Mr. George of 

 Leeds, by transmitting chlorine over metallic titanium at a red 

 heat. It is a transparent colourless liquid, resembling bichlo- 

 ride of tin, and boiling a little above 212. The density of its 

 vapour is 6.615 (Dumas). Bichloride of titanium combines with 



R R 



