182 HALL AND SMITH— COLUMBIUM. [May 19, 



Specific gravity of oxide (B) : 



18 5924 pyknometer -\- water, t = 18 



.2346 gram of oxide taken 

 18.8270 

 18.7760 pyknometer -f- water -j- oxide .2346 



.0510 gram water displaced .0510 4.60 sp. g. 



To determine the titanium content of the columbium oxide re- 

 course was had to a comparison of the color tint produced by 

 hydrogen peroxide in an oxalate solution against known amounts 

 of titanium hydrate dissolved in oxalic acid. Thus, 0.2262 gram 

 of columbium oxide was fused with acid potassium sulphate and the 

 fusion dissolved in oxalic acid and diluted to 50 cubic centimeters. 

 It gave a color equivalent to 0.4 cubic centimeter of the standard 

 titanium solution (1 c.c. contained 0.00106 gram of titanium 

 dioxide). In other words, by this test the columbium oxide was 

 thought to contain 0.000424 gram of titanium dioxide, or .18 °/ c . 



Solubility of Crystals A. 

 One part of the salt was found to be soluble in a little over 12 

 parts of water. This is the solubility of potassium columbium 

 oxyfluoride. 



100 grams of the residues obtained by the evaporation of mother- 

 liquors (page 180) to dryness were dissolved in water and fraction- 

 ally crystallized. After having removed as much of the tantalum as 

 possible by introducing dilute potassium hydroxide into the boiling 

 solution until a rather considerable and permanent precipitate was 

 obtained, the solution was boiled for some time. The first fraction 

 of crystals (2) and the third fraction of crystals (3) were removed, 

 after which hydrofluoric acid was added to the mother-liquor, from 

 which there separated a crop of needles, which we shall designate 

 crystals 4. These last were recrystallized from hydrofluoric acid. 

 They probably contained silicon and tantalum. The acid mother- 

 liquors from these different crops of crystals were treated as de- 

 scribed by Hermann (J. pr. Chan., Series 2, vol. 15, 105, 1877). 

 That is, they were treated with 20 parts or two liters of water ami 

 150 grams of sodium hydroxide. A clear solution resulted, from 

 which a fine crystalline precipitate separated. The filtrate from 



