450 DR T. THOMSON'S Analysis of some Minerals. 



ter edulcoration, drying, and ignition, 0.44 grain. The potash- 

 ley had dissolved the alumina of the precipitate, which obviously 

 amounted to 0.585 grain. Thus the brown precipitate thrown 

 down by caustic ammonia, was composed of, 



Silica, 0.055 



Peroxide of iron, . . . 0.440 

 Alumina, 0.585 



1.080 



The muriatic solution was now mixed with a sufficient quan- 

 tity of carbonate of ammonia, to throw down the whole of the 

 barytes. The filtered liquid was evaporated to dryness, and ex- 

 posed to a graduated heat, to drive off the ammoniacal salts. 

 The residue was found to contain lime derived from the filter. 

 To get rid of it, I added some carbonate of ammonia, heated the 

 liquid in a flask, then left it in a small glass cylinder till the car- 

 bonate of h'me subsided ; drew off the clear supernatant liquid 

 by a sucker, edulcorated the carbonate of lime by distilled wa- 

 ter, which was drawn off in like manner by a sucker. The liquid 

 was evaporated to dryness in a platinum vessel, and the ammo- 

 niacal salt driven off. There remained behind a little saline 

 matter, which weighed, after ignition, 0.84 grain. It was soluble 

 in water, and the aqueous solution was abundantly precipitated 

 by muriate of platinum. Hence the salt was chloride of potas- 

 sium, and contained 0.41 potassium, equivalent to 0.53 potash. 



The 4 grains of silica, obtained at the beginning of the analy- 

 sis, were mixed with thrice their weight of anhydrous carbonate 

 of soda, and exposed to a strong heat in a platinum crucible. The 

 mass, which had undergone fusion, was dissolved in muriatic acid, 

 and the solution was evaporated to dryness. The dry residue was 

 digested in dilute muriatic acid, and thrown upon a filter, to se- 



