448 COMPOUND SALTS, CONTAINING 



more soluble than potash alum. For I find that 

 at the temperatue of 60, 100 parts of water 

 dissolve 



9'37 parts of ammoniacal alum 

 14-79 parts of potash alum 

 327 '6 parts of soda alum. 



This great solubility would make soda-alum 

 more convenient for the use of dyers and prin- 

 ters than common alum, if it could be procured 

 with the same facility. When soda-alum is 

 heated on the sand bath, it undergoes very 

 nearly the same loss of weight as common alum. 

 For 100 parts in my trials lost 44'1 parts of wa- 

 ter of crystallization. 



I found by experiment that 58*875 grains of 

 the crystals of this alum are just decomposed by 

 53 grains (13-25 x 4) of chloride of barium, and 

 consequently, contain exactly 20 grains of sul- 

 phuric acid. From 58*875 grains of the same 

 crystals, I got almost exactly 6*75 grains of alu- 

 mina and 9*5 grains of anhydrous sulphate of 

 soda; the excess, amounting to 0%5 grain, was 

 owing to sulphate of lime obviously derived 

 from the filter. From this analysis it follows 

 that the constituents of soda-alum are 



3 atoms sulphate of alumina 2 1 -75 

 1 atom sulphate of soda 9 



2, f> atoms water 28-125 



58-875 



