Chemical Examination of American Minerals. 21 



of this salt, amounts to only 22*5 grains ; the 2*29 grains of 

 excess, were owing to the escape of a portion of the sulphuric 

 acid. 



The analysis of this salt was conducted in the following 

 manner. 



1. By a few trials, it was ascertained that when 53'25 grs. 

 of the alum previously dissolved in water, are mixed with a 

 solution of 54 grains of anhydrous chloride of barium, sul- 

 phate of barytes falls down, and the supernatant liquid is 

 neither affected by muriate of barytes, nor sulphate of soda. 

 Hence 53'2r> grains of this alum contain just 20 grains of 

 sulphuric acid. 



2. 53*25 grains of the alum were dissolved in water, and 

 mixed with a solution of 26*25 grains (=8-75X3) of recently 

 ignited and pure carbonate of potash. An efi'ervescence took 

 place, and a white precipitate fell, which being collected and 

 dried on the filter, weighed 14" 15 grains. But by ignition 

 was reduced to 7-05 grains. The liquid after the separation 

 of the white precipitate, was heated to the boiling tempera- 

 ture, but no additional precipitate fell. Being tested by litmus 

 paper, and by cudbear paper, it was found perfectly neutral, 

 showing that 15 grains of the sulphuric acid had been in com- 

 bination with the precipitate thrown down ; and that the re- 

 maining 5 grains of the acid, had been in combination with 

 an alkali. Carbonate of ammonia was now added to the 

 liquid, but no more precipitate fell. 



The precipitate which was white, and obviously consisted 

 chiefly of alumina, was re-dissolved in muriatic acid, evapo- 

 rated nearly to dryness, diluted with water, and mixed and 

 boiled with a quantity of caustic potash-ley. The precipi- 

 tate, which had at first fallen, was gradually re-dissolved 

 with the exception of a dark colored reddish matter, which 



