ALB1TE. 



47 



ough washing with warm water, but this was not sufficient to remove 

 all the tungstate. A determination of tungstic acid showed 0.62 per 

 cent still present, which is equivalent to 0.78 per cent of sodium tungs- 

 tate. After removing the water by heating carefully to a dull redness, 

 the product was submitted to a microscopic examination, which 

 showed it to be entirely crystalline and apparently homogeneous. 

 Determinations of the specific gravity gave 2.620 (see table, p. 58). 

 If this is corrected for 0.78 per cent of sodium tungstate of specific 

 gravity 4.2, we obtain 2.607. 



A portion of the preparation was then purified further by fusing 

 for a few minutes with acid sodium sulphate (Hautefeuille) at as low 

 a temperature as practicable, after which the excess of sulphate was 

 extracted with water and the product dried (the temperature was 

 raised to a dull red heat to remove all water) and analyzed. 



The specific gravity of it was 2.604, which may be corrected as 

 before for the remaining trace of tungstic acid assumed to be in the 

 form of the sodium salt. The value then falls to 2.601. 



A second portion of the same albite was purified by another process. 

 Instead of fusing with acid sodium sulphate, the powdered sample 

 was first digested for a short time with dilute hydrochloric acid (1:1), 

 which set free tungstic acid. The excess of hydrochloric acid was 

 removed with water, the tungstic acid with ammonia, and finally the 

 excess of reagent and the ammonium tungstate by further washing 

 with water. When dried at a low red heat, the preparation had the 

 following composition : 



