ALUMINA. 317 



small. I shall state one or two of the experi- 

 ments numerically, that the reader may judge of 

 the approximation. 



(i.) 18*92 grains of alumina, dried on the fil- 

 ter in a temperature of 100, being exposed to a 

 strong red heat, were reduced to 13*49 grains ; 

 consequently, the water driven off amounted to 

 5 '43 grains. Now, 



13-49 : 5-43 : : 2-25 : 0*9055 = ratio of water. 



(2.) 20 grains of alumina, which had been left 

 upon a filter for three months, in a temperature 

 which, during the day, was usually 85, though 

 during the night it was lower, as the fire was al- 

 lowed to go out, being exposed to a strong red 

 heat, was reduced to 13'45 grains ; and, conse- 

 quently, it had lost 6*55 grains. Now, 



13-45 : 6-55 : : 2-25 : 1-099 = ratio of water. 



It appears from this experiment, that by a great 

 length of time the alumina may be brought into 

 the state of a hydrate, consisting of 1 atom alu- 

 mina and 1 atom water ; for 1-099 is only a very 

 little less than 1*125, the weight of an atom of 

 water. 



Such are the results which I have obtained 

 respecting the atomic weight of alumina. They 

 all conspire to show that it is very nearly 2*25, 

 and that it cannot by any means amount to a 



