i9°5-] 



MALL AND SMITH— COLUMBIUM. 209 



0.3470 gram of the oxide from the yellow fluoxypercolumbate 

 was dissolved in oxalic acid and chromotropic acid and diluted to 

 50 c.c. It gave a very slight pink color, about equal in intensity 

 to the color developed in 50 c.c. by .000025 gram Ti0 2 in the same 

 amount of oxalic acid on treating with chromotropic acid. This 

 would correspond to less than .01 per cent, of TiO, and is likely 

 not very far wrong. 



From these experiments it may safely be concluded that the 

 color produced in hydrofluoric acid solution of columbium with 

 hydrogen peroxide is not due to the presence of titanium. Also 

 it is likely that columbium itself gives a distinctive color with 

 hydrogen peroxide, equivalent to from .10 per cent, to .15 per 

 cent, of its weight of Ti0 2 , yet yellow green instead of straw 

 yellow, as is given by titanium in dilute solutions. Possibly there 

 may still be present some other element. For this careful search 

 will be made. 



PREPARATION AND ANALYSIS OF THE YELLOW OXIDE 

 OF COLUMBIUM. 



Hydrated oxide of columbium, containing ten grams of oxide, 

 was prepared by decomposing the double fluoride with sulphuric 

 acid, evaporating off the excess of acid and extracting with boiling 

 water. This hydrate was washed repeatedly with boiling water 

 and air dried. It was covered with about 20 c.c. of concentrated 

 hydrochloric acid and brought to boiling for several minutes, until 

 all of the lumps had thoroughly disintegrated, when it was diluted 

 to about three times its original volume with water. All but a few 

 particles were dissolved. This solution was filtered and an equal 

 volume of three per cent, hydrogen peroxide added. It became 

 yellow and after a few minutes a yellow precipitate appeared. The 

 solution was allowed to stand over night. The precipitate was 

 then filtered out, washed with cold water, in which it was insoluble, 

 and air dried. 



Under the above conditions about one quarter of the oxide in 

 solution was precipitated by the hydrogen peroxide. If the re- 

 mainder of the oxide in solution were recovered and dissolved in 

 hydrochloric acid, as before, a fresh portion of it could be pre- 

 cipitated on adding hydrogen peroxide. The air-dried precipitate 

 lost oxygen and water on ignition and regained its white color. 



