Constituents of various Minerals. 251 



According to ARFVEDSON, its constituents are, 



Alumina, . . . . 81.43 

 Silica, 18.73 



100.16 (Kongl. Vetens. Acad. 

 Handl 1822, p. 90). 



While SEYBERT found the composition in two different speci- 

 mens as follows : 



Alumina, .... 73.60 . . . 68.666 



Glucina, .... 15.80 . . . 16.000 



Silica, 4.00 . . . 5.990 



Protoxide of iron, . 3.38 . . . 4.733 



Oxide of titanium, . 1.00 ... 2.666 



Moisture, .... 0.40 . . . 0.666 



98.18 . . . 98.730 



The first of these specimens was from Hoddam ; the second from 

 Brazil. (SILLIMAN'S Jour. 8. 109.) 



M. ARFVEDSON'S analysis was conducted, by fusing the pound- 

 ed chrysoberyl with caustic potash, and digesting the matter in 

 muriatic acid. This process was repeated, and the portion 

 which ultimately resisted the action of the muriatic acid, he con- 

 sidered as silica. This was very unlikely to be a correct view 

 of the case. The silica, if any be present, ought to be more 

 easily removed by fusion with caustic potash, than any of the 

 other constituents. I analysed chrysoberyl immediately after 

 seeing SEYBERT'S analysis, and found that the portion remaining, 

 after the first fusion of the mineral with caustic potash, and di- 

 gestion in muriatic acid, is a combination of glucina and oxide 



VOL. XI. PART II. K k 



