40 



On the Chemical Composition of Harmotome. 



BARYTIC HARMOTOMBL 



I may take this opportunity of mentioning, that after I had 

 detected alkalies in barytic harmotome, it occurred to me to ex- 

 amine Brewsterite again for alkahes by the same process, which 

 was applied to the former mineral ; my previous researches for 

 alkalies in Brewsterite having been made by decomposing it by 

 carbonate of baryta, and throwing down the baryta by carbon- 

 ate of ammonia, a method which renders necessary the ultimate 

 expulsion by heat of a very large quantity of ammoniacal salt, 

 which is apt to carry along with it small quantities of fixed chlo- 

 rides- I accordingly treated a small quantity of powdered Brew- 

 sterite with muriatic acid, leaving them in contact for some days, 

 and occasionally applying heat. By the process already detail- 

 ed, I ultimately obtained a minute quantity of cubical crystals ; 

 and, on examining those by muriate of platinum, they seemed 

 to be entirely chloride of sodium, at least operating with the 

 small quantity of materials which I used, I could not detect 

 potash. The minute quantity of soda is of course in addition 

 to stroDtia, baryta, and the other constituents which I formerly 

 mentioned in Brewsterite. When my time permits, I intend to 

 execute another analysis of the mineral, to ascertain the exact 

 proportion of alkali k contains. 



