154 FLUORITE. 



84. FLUORITE. 

 CaF. 



A weighed quantity of the finely-powdered mineral 

 is mixed, in a platinum crucible, with concentrated 

 sulphuric acid, and heated until all the hydrofluoric 

 acid is expelled, and the greater excess of sulphuric 

 acid volatilized. The residual sulphate of lime is then 

 mixed with alcohol, filtered off, washed with alcohol, 

 ignited and weighed. Or it may be dissolved in water 

 containing hydrochloric acid, the solution mixed with 

 ammonia, and the lime precipitated by oxalate of 

 ammonia. 



The fluorine is determined from the loss. In order 

 to estimate it directly, the decomposition must be effected 

 in a platinum retort, the vapors of hydrofluoric acid 

 conducted into solution of carbonate of soda, and the 

 fluorine precipitated from the solution by chloride of 

 calcium, as in the analysis of topaz. 



Or the very finely-powdered mineral maybe mixed 

 with an excess that is, with at least an equal weight 



Fig. 15. 



