208 HALL AND SMITH— COLUMBIUM. [May 19, 



observed in the case of the columbium as free from titanium as it 

 could be obtained. Although the columbium oxide used for these 

 tests had passed through several manipulations which should re- 

 move molybdenum, such as, fusion with sodium carbonate and sul- 

 phur, changing to chloride with sulphur monochloride and dis- 

 tilling off the more volatile portion, it was thought best to determine 

 how much molybdenum would be required to give a test equal to 

 that obtained from the purest oxide of the columbium at hand. 

 To this end weighed amounts of molybdenum were dissolved in 

 oxalic and sulphuric acids, and the color, developed with hydrogen 

 peroxide, compared with that obtained with a standard titanium 

 solution of hydrogen peroxide. 



1. 0.2780 gram of molybdic acid developed a color equivalent 

 to 0.0048 gram Ti0 2 , or 0.0058 gram of molybdic acid will give a 

 color equal to that given under similar conditions by 0.0001 gram 

 Ti0 2 . 



2. 0.0660 gram of molybdic acid gave a color equal to 0.0015 

 gram Ti0 2 , or 0.0044 gram of molybdic acid is equal to 0.0001 

 gram Ti0 2 . 



The variations in these results is due to the difficulty in matching 

 the different shades as to intensity of color. The average is about 

 right, or 0.0050 gram of molybdic acid is equivalent to 0.0001 

 gram TiO.,. Calculating on this basis, the best oxide of columbium 

 obtained, which gave a color equivalent to . 1 2 per cent TiO.,, 

 would contain 6 per cent, of MoO s if the color was due to the 

 presence of molybdenum, which would be impossible after the 

 treatments through which the oxide has passed. It had been 

 crystallized twice as potassium oxyfluoride, fused with sodium car- 

 bonate and sulphur, the tantalum removed, again crystallized as 

 the oxyfluoride of potassium and twice from hydrofluoric as potas- 

 sium columbium fluoride, then changed to chloride in sulphur 

 monochloride, the sulphur monochloride and the more volatile 

 portions distilled off and rejected, again changed to oxide and this 

 treatment with sulphur monochloride repeated. The final oxide 

 was converted into potassium fluoxypercolumbate and crystallized 

 once from hydrogen peroxide and hydrofluoric acid. This salt 

 was yellow in color, and 0.3540 gram of oxide from it, dissolved 

 in oxalic acid, gave with hydrogen peroxide a color equivalent to 

 0.000424 gram TiC) 2 , or .12 per cent. At the most it could not 

 have contained more than a bare trace of oxide of molybdenum. 



