no. 2376 



CREEDITE FROM COLORADO— FOSHAO. 



423 



CHEMICAL COMPOSITION. 



Creedite is easily and completely soluble in hydrochloric and sul- 

 phuric acids. For the analysis clear, colorless crystals were selected, 

 crushed, and examined under the microscope. The material so 

 selected was homogeneous and without a trace of foreign matter. 

 The mineral was dissolved in sulphuric acid and evaporated to dense 

 fumes to expel the fluorine, and the lime and alumina determined in 

 this portion by the ordinary methods. Sulphate was determined in 

 a separate portion dissolved in hydrochloric acid by precipitation as 

 barium sulphate. Fluorine was determined by Penfield's method, 

 volatilizing as silicon fluoride and absorbing in a 50 per cent alco- 

 holic solution of potassium chloride and titrating this solution with 



1 1 1 1 ~y 



1»- — it u 



- '- u 



o ,i 



I! 1! , 



■I 1 1 I ^ 



Fig. 3.— Gnomonic projection of the forms on creedite. 



standard sodium hydroxide. Preliminary tests of this method with 

 the apparatus employed gave somewhat high results, due, perhaps, 

 to the imperfect condensation of the sulphur trioxide fumes. Water 

 was determined by Penfield's method. The results together with 

 the ratios derived therefrom are given in the following table: 



Analysis and ratios of creedite. 



