206 HALL AND SMITH— COLUMBIUM. 



[May 19, 



0.7482 gram of salt lost 0.0784 gram on ignition, i. e., 29.1 

 c.c. of oxygen at 24 and under 742 mm. pressure, or 0.0374 

 gram, the difference — 0.0410 gram — being water. 



Calculated. Found. 



K 2 SO, 54.89 54-85 



Oxide 42.28 42.34 



O (active) 5.05 5.00 



H 2 5.68 5. 48 



Hence it may be concluded that the salt obtained from strong 

 hydrofluoric acid is the same as that got when hydrofluoric acid 

 is not used. 



It would seem impossible to obtain a derivative of percolumbic 

 acid which does not contain oxygen. 



The salt separates from solutions containing hydrofluoric acid in 

 large well- formed plates, which may be easily measured. They 

 are much easier to handle than when crystallized from a solution 

 free from acid. The crystals are always greenish yellow in color. 



Piccini states that the salt obtained by him had a slight yellow 

 tint, but that this color was completely removed by two recrystal- 

 lizations from hydrogen peroxide. The salt obtained above was 

 recrystallized six times from hydrogen peroxide containing hydro- 

 fluoric acid. The crystals from the last crystallization were fully 

 as highly colored as those which had not been recrystallized. They 

 were then recrystallized twice from hydrogen peroxide containing 

 no acid. The resulting salt was practically colorless, but it dis- 

 solved in water and hydrogen peroxide with a yellow color, which 

 was intensified by the addition of hydrofluoric acid and on evapor- 

 ating again to crystallization the crystals were as highly colored as 

 any obtained previously. 



The oxide from the double fluoride, originally used, gave a color 

 equivalent to 0.4 per cent. Ti0 2 . It was supposed that this color 

 was due entirely to titanium and that the yellow color of the solu- 

 tion and of the crystals of potassium fluoxypercolumbate was also 

 due to this element. To test this supposition 100 grams of the 

 purest potassium columbium oxyfluoride was crystallized twice from 

 strong hydrofluoric acid. The crystals obtained were decomposed 

 with concentrated sulphuric acid, and the hydrate after extraction 

 with water ignited to oxide. The color which this oxide devel- 

 oped in oxalic acid solution with hydrogen peroxide was equivalent 



