298 EARTHS PROPER. 



whole ; and -p^d part of 0-6868 = 0-3557. This 

 being subtracted from 0-6868 leaves 0-3311, 

 which must be taken from 22-844, leaving 22-513 

 for the silica actually combined with the alumi- 

 na in the mineral. And 



Gives 



2-2831. 22-513 : 25'7 : : 2 : 2-2831 = the atomic weight of alumina. 



7 BUCHOLZITE. 



Buchoizite From the account of this mineral given in page 

 175 of this work, it appears that its constituents, 

 according to Brande's analysis, are as follows : 



Silica .... 46 



Alumina ... 50 



Oxide of iron . . . 2-5 



Potash .... 1-5 



100-0 



And that the silica united to the alumina in 

 this mineral is 44*391 grains. Now, 



Gives 



2-2527.' 44-391 : 50 : : 2 : 2-2527 = an atom of alumina. 



8. LEUC1TE. 



Leucite This mineral, which abounds so much in the 

 neighbourhood of Mount Vesuvius, and which 

 always occurs crystallized, was found by Arfwed- 

 son to be composed of 



Silica . . . . 56-1 



Alumina . . . 23*1 



Potash . . . 21. 15 



Oxide of iron . 



101-3 



