184 HALL AND SMITH— COLUMBIUM. [May 19, 



Analysis of recrystallized portion of crystals (4), page 182. 



.5588 gram of sample gave .2407 gram of oxide. 



.3232 gram potassium sulphate. 

 .2407 : 3232 :: x/2 : 174 x= 259.2. 



Calculated. 

 K 2 CbF 7 . Found. 



Oxide 43-93 43-° 8 



K,S0 4 57-05 57-84 



The results of analysis as well as the behavior points to the fact 

 that the oxide contained in these residues is mainly columbium 

 oxide, Cb 2 5 , with a small portion of another oxide causing the 

 equivalent weights obtained to be too low. These results may in 

 part be due to the presence of some potassium silicofluoride, but 

 more likely to potassium titanium fluoride. Yet these last fractions 

 of double fluoride in which the titanium should be concentrated 

 show only very small amounts. Starting with so much material 

 the last fractions should show more titanium if it is present in the 

 mineral in appreciable amounts. 



The only test for small amounts of titanium which we have are 

 the hydrogen peroxide test of Schonn, Jahresberichte, 1893, 901, 

 and the chromotropic acid test used by Geisow (Dissertation, 1902). 

 Of these the former is the only one relied on, and it offers the only 

 direct evidence which we have for the presence of titanium in the 

 potassium columbium oxyfluoride obtained from columbite. 



The methods applicable in the preparation of columbium oxide 

 relatively free from titanium are as follows : 



1. Crystallization of potassium columbium fluoride (K 2 CbF 7 ) 

 which is not isomorphous with potassium titanium fluoride. The 

 difficulty in this case is that the hydrofluoric acid increases the 

 solubility of the columbium body and decreases that of the titanium 

 double fluoride so that the titanium would have less tendency to 

 concentrate in the mother liquors. 



2. Fractional precipitation with dilute ammonium hydroxide. 

 The columbium hydrate is precipitated first and the titanium con- 

 centrated in the last fractions. No fraction consists entirely of 

 titanium hydrate ; even the last fraction is largely columbium 

 hydrate. 



3. The formation of the chloride or oxychloride of columbium 

 and the chloride of titanium and separating these by distillation. 



