312 EARTHS PROPER. 



Sulphuric acid 33-85 or 20-6060 



Alumina . 10-86 - 6-5958 



Potash . 9'90 - 6-0266 



Water . 45-00 - 27'3940 



99-61 60-6224 



Loss . . . . 0-2526 



60-8750 



According to this analysis, 3 atoms of alumina 

 weigh 6 '5 958. Consequently, the weight of the 

 atom of alumina is 2*1986, which is a little less 

 than the result of my analysis of alum. 



In a subsequent chapter of this work, when 

 I come to treat of the salts of alumina, it will be 

 seen that the atomic weight of alumina just 

 given, is corroborated by many other aluminous 

 salts which have been subjected to examina- 

 tion. 

 Mr. Phil- Mr. Phillips' opinion, that the atomic weight of 



lips' experi- ... 



ment re- alumina is 3*375, seems, as far as I can judge, 

 u! to be founded on the following experiment. He 

 found that when moderately diluted, sulphuric 

 acid was digested for a long time upon an ex- 

 cess of recently precipitated alumina, till it re- 

 fused to take up any more ; the liquid, when 

 filtered, had a tendency to precipitate a peculiar 

 sulphate of alumina in white flocks ; the liquid, 

 when dropped into water, rendered it milky, and 

 a white sediment was deposited. He analyzed 



