146 ULEXITE. 



volatilized ; after exposure for a considerable time to 

 a temperature of 100, the residue is heated with water 

 containing hydrochloric acid, the silicic acid filtered 

 oft) washed, dried and ignited. 



The filtrate is neutralized with ammonia, and the 

 lime precipitated by oxalate of ammonia (No. 12). 



By this process the boracic acid cannot be deter- 

 mined directly but only by difference, because a large 

 part of it volatilizes during evaporation. In order to 

 make a direct determination, the mineral is decomposed 

 by hydrochloric acid, or a retort furnished with a re- 

 ceiver, distilled to dryness, and the distillate containing 

 the boracic acid poured back upon the residue, with 

 which it is digested for some time, and then filtered 

 from the silicic acid. The lime is then precipitated 

 by a large excess of oxalate of potassa, filtered, and 

 the filtrate concentrated by evaporation. From this 

 the boracic acid is precipitated as a double fluoride of 

 boron and potassium. For this purpose it is placed in 

 a platinum dish with a little potassa, then mixed with 

 a small excess of hydrofluoric acid, and evaporated to 

 dryness. For the separation of the other salts, the 

 mass is treated with a moderately concentrated solution 

 of acetate of potassa, allowed to stand for some time, 

 and the double fluoride of boron and potassium thrown 

 upon a weig'hed filter, and washed with the solution of 

 the acetate. The acetate of potassa is then washed out 

 with alcohol. The double fluoride is dried at 100 

 and weighed. 



79. ULEXITE. 

 . NaO, 2BoO 3 +2 (CaO, 2BoO 3 ) +18HO. 



After determination of the water the mineral is dis- 

 solved in hydrochloric acid, neutralized with ammonia, 



