194 







G. HARKER. 









(Analysis continued) 

 Lime ... 



1 2 



New South Wales. 



10-32 9-61 



3 



Veltlin. 



9-90 



4 



Thannbergthal. 



10-96 



5 



Rameui-Brod 



11-23 



Soda ... 





5-11 



undeter. 



5-23 



4-36 



4-62 



K 2 





none 



•29 



•80 



1-15 



•42 



MgO 





none 



•28 









H 2 on ignit. 



undeter. 



•13 



■67 



•65 





100-63 incompl. 100-90 100-41 100-53 



Nos. 1 and 2 are analyses of two different samples of the mineral. 

 In the first analysis the ferric oxide was not determined separately 

 30*15 is the percentage of mixed oxides of iron and alumina; 

 the analysis was done on the dried ignited sample. Nos. 3, 4, 

 and 5 are three analyses of labradorite given in Dana, and are 

 put in for sake of comparison. The silica in the labradorite 

 analyses given in Dana varies from 52*45 to 56*18, the alumina 

 from 27*33 to 29*85, the lime from 9*90 to 12*01, and the soda 

 from 3-90 to 5*23. From these it will be seen that the chemical 

 composition of the mineral agrees well with that of labradorite, 

 and taken in conjunction with its physical properties shews that 

 it is that mineral. 



Topaz. 



The following investigation was also made in the Chemical 

 Laboratory of the University of Sydney at the suggestion and 

 under the direction of Professor Liversidge, with the object of deter- 

 mining the composition of some N. S. Wales specimens and of 

 comparing certain of the published methods for the analysis of 

 fluorides. The most difficult constituent to analyse in topaz is 

 fluorine, for the estimation of which a number of methods have 

 been proposed. To find the most satisfactory was the first object 

 in view. 



Before proceeding farther a resume' of previous methods for the 

 determination of fluorine might be of use : — 



(a) Fluorides not decomposable by sulphuric acid. — Berzelius 

 was the first to accomplish the analysis of fluorides undecomposable 

 by sulphuric acid. He fused the fluorides with alkaline carbon- 



^ 



