210 HALL AND SMITH— COLUMBIUM. [May i >; 



As the precipitation of the columbium was only partial it was 

 best to be certain of the identity of the portion precipitated. To 

 this end 2.5 grams of the yellow oxide were obtained, ignited to 

 remove the excess of oxygen, and changed to the potassium double 

 fluoride. This analyzed as follows : 



0.6822 gram of the salt gave 0.3026 gram of oxide and 

 0.3966 gram of K 2 SO t 



Calculated. Found. 



Oxide 44-52 44.36 



K 4 S0 4 57.S1 5S.14 



Hence the compound obtained is a derivative of columbium. 



Columbium is not precipitated from the solution remaining after 

 the yellow precipitate has been filtered out, by an excess of ammo- 

 nium hydroxide, until the hydrogen peroxide in the solution has 

 been destroyed. 



Analysis of the yellow precipitate : 



0.1917 gram of sample gave 0.1298 gram of Cb 2 0.. 

 0.2556 gram of sample gave 7.8 c.c. of oxygen at 22 and under 

 741 mm. pressure, equal to 0.0101 gram. 



Percentage. Ratio. 



Cb 2 Q 5 67.71 I. OOO 



O (active) 3.95 0.984 



H 2 (difference) 28.34 6.240 



100.00 



This corresponds to Cb(OH) 6 , or to Cb 2 5 H 2 2 5H 2 0. 



Melikoff and Pissarjewsky (Zeit. anorg. Chem., 20, 340) obtained 

 a percolumbic acid of the formula HCb0 4 + «H 2 0, by heating 

 columbium hydrate with 30 per cent, hydrogen peroxide on a 

 water bath. They also obtained it by adding sulphuric acid to a 

 solution of sodium percolumbate, dialyzing out the excess of sul- 

 phuric acid and the potassium sulphate, then evaporating the clear 

 yellow solution to dryness on a water bath. They describe it as a 

 yellow amorphous powder, insoluble in water. 



The color of these higher oxides seems characteristic of colum- 

 bium and is certainly not due to the presence of titanium. The 

 hydrate obtained by Melikoff and Pissarjewsky contained twice as 

 much active oxygen, in proportion to the columbium, as did the 

 hydrate obtained during this investigation. 



