72 On the Chemical Composition of Norwegian Minerals. 



Mineral employed, 



Impure Silica obtained, 



Titanic acid, from do., . 



Titanic acid, from solution, 



Titanic acid, with trace of iron, 



Silica, from ammoniacal precipitate. 



Yttria, 



Sulphate of lime, 



Sesquioxide of iron, 



Alumina, 



Glucina, 



Oxide of manganese, 



From which the following percentage 

 tained : — 



In 22-78. In 100. 



22-78 grs. 



7*66 . 



•59 . 



•32 . 



6-39 . 



0-07 . 



1-09 . 



10-80 . 



1-63 . 



1-83 . 



0-12 . 



0-07 . 



results will 



be ob- 



Silica, . • • . . 7*14 



Titanic acid, . . . 6-39 



Alumina, .... 1-83 



Glucina, . . . . *12 



ime, 4-45 



Yttria, 1-09 



Protoxide of iron, . 1*56 

 manganese, *06 



31-33 



28-84 



8-03 



•52 



19-56 



4-78 



6-87 



•28 



Oxygen. 



15-06) 



11-18/ 



3-75\ 



•32] 

 5-56^ 



•95 

 1-52 



•06 



26-24 



4-07 



8-09 



12-16 



22-64 99-41 

 This analysis agrees pretty well with those of Erdmann 

 and Scheerer, with the exception that the yttria is not more 

 than half the amount found by them, and the lime and alu- 

 mina are both somewhat higher. Erdmann gives the for- 

 mula, as 



3Ca 3 si 2 +&Si + Yf 3 



which, however, does not seem to be correct, as he supposes 

 the titanic acid to be entirely combined with the yttria, which 

 here is evidently not the case. It seems probable to me 

 that the yttria only replaces a part of the lime, and although 

 it may be an essential ingredient, in so far as^it may never be 

 absent, still it most probably does not play so important 

 part as to show itself in the formula. Supposing the titanic 

 acid to play the part of a base, we shall find that the^oxygen 

 of the base to that of the silica will not be far from the 

 ratio of 3 : 2, not farther indeed than the several analyses 



