190 THE MINERALS OF TASMANIA. 



" Rearranging according to solubility, we have as fol- 

 lows : — 



'' I have allowed a small disparity to creep in here in 

 the fluorine. The amount actually found in the '' insol- 

 ubles ' was 12'6 per cent.; the total was 15*9, leaving for 

 the soluble part F 3'3 per cent. The 3'57 per cent. Ca^ 

 however, require 3*42 F, giving a total of 6*99. To sim- 

 plify matters, and in view of the difficulty of determin- 

 ing fluorine, I have taken this 6-99 rather than leave any 

 of the CaO free, which would be an unnecessary complica- 

 tion. 



" Taking the ' insoluble ' portion alone, we find that its 

 percentage composition is — 



Per cent. 

 Si O2 = 33-19 



Al, O3 = 52-69 



F = 14-12 



100-00 



Now% it is quite possible that one is acting correctly in 



adding the ' soluble ' alumina to that in the ' insoluble,' 



for the reason that doubtless topaz is affected by acids, 



just as it is affected by heat, so as to suffer a decrease in 



weight. If the ' soluble ' and ' insoluble ' alumina are 



taken together, and the CaF.^ is excluded, then the figures 



become as follow : — u * 



Per cent. 



Si O, = 29-6 



Al^ O3 = 510 



F = 12-6 



P3-2 

 Ca F2 = 6-99 



Loss, H2 O, 100-19 



HO, F = 4-8 



104-99 



