308 EARTHS PROPER. 



phate of soda and muriate of barytes, but was 

 not affected by either ; showing that it contained 

 no sensible quantity of barytes or sulphuric acid. 

 It follows from this experiment, that the sulphu- 

 ric acid in 60-875 grains of alum is just saturated 

 by the barytes from 53 grains of chloride of 

 barium. But 53 is equal to 13-25 x 4 ; and 

 13-25 grains of chloride of barium require just 

 5 grains of sulphuric acid to saturate all the ba- 

 rytes which they yield. It is obvious from this, 

 that 60-875 grains of alum contain exactly 20 

 grains of sulphuric acid. 



2. 60-875 grains of alum crystals were put 

 into a platinum crucible, which was left for an 

 hour on a hot sand bath. After it had been re- 

 duced to the state of burnt alum by the loss of 

 its water of crystallization, it was introduced 

 into a wind furnace, and kept for an hour in a 

 bright red heat. The loss of weight sustained 

 was 43-62 grains. 



The alum thus treated, was digested in dis- 

 tilled water, and then thrown upon the filter. 

 The alumina left upon the filter was washed 

 till the liquid which passed through ceased to 

 precipitate muriate of barytes. The liquid which 

 passed through the filter was concentrated on 

 the sand bath, and then precipitated by muriate 

 of barytes. The sulphate of barytes obtained, 

 after being washed, dried, and heated to redness, 

 weighed 13-28 grains, which is equivalent to 



