19 o S .] HALL AND SMITH— COLUMBIUM. 207 



to 0.24 per cent, of its weight of titanic acid. It was now heated 

 in sulphur monochloride and converted into chloride. The latter, 

 together with the excess of monochloride, was collected in a re- 

 ceiver and the sulphur monochloride distilled out in the hope that 

 any titanium tetrachloride present would be expelled with it. The 

 chloride remaining after removing the sulphur monochloride was 

 converted into oxide. It contained titanic oxide equivalent to 

 o. 16 per cent. The oxide was again heated in sulphur monochlor- 

 ide and treated as before. After the second treatment the titanic 

 oxide equivalent was .12 per cent, and the color now developed 

 was different. It was greenish yellow instead of yellow inclining 

 towards red, which is characteristic of titanium. About five grams 

 of the oxide which had passed through this treatment were changed 

 to double fluoride and crystallized from hydrogen peroxide and 

 hydrofluoric acid. Its solution, in hydrogen peroxide, was yellow 

 and its color increased in intensity on adding hydrofluoric acid. 

 The crystals from it were canary yellow with a tint of green, dif- 

 fering in no respect from those previously obtained. 



About ten grams of this yellow salt were next dissolved in water 

 and hydrogen peroxide. This solution was distinctly yellow in 

 color. It was divided into two portions. To one portion 0.5 

 gram of potassium titanium fluoride was added. The color in this 

 portion became considerably deeper, but the excess of color was 

 completely discharged upon adding hydrofluoric acid, the two 

 solutions becoming again identical in color. 



Potassium titanium fluoride dissolved in hydrogen peroxide to a 

 deep yellow-colored solution. On cooling crystals were deposited, 

 which were not yellow but colorless when completely free from 

 mother liquor. The addition of hydrofluoric acid to the colored 

 solution completely destroys the color, and in the presence of 

 hydrofluoric acid the salt formed is white, resembling potassium 

 titanium fluoride. When air dried it gives off neither water nor 

 oxygen on ignition. 



The only elements which give a distinctive color in acid solution 

 with hydrogen peroxide and which might occur here are titanium, 

 vanadium and molybdenum. Of these the first has been excluded 

 and the second also by reason of the color which it gives (red to 

 rose red). There still remains molybdenum. Its color in an 

 oxalic acid solution with hydrogen peroxide is identical with that 



