250 ANALYtrS. 



Defcriptbn and criiclblc wa<;covcred with a piece of glafs, and placed in warm 



analyfisot a ^^^^ q,^ fexaminalion of the crucible and its contents, after 



mineral from .... , . , r . • i 



CoviwalL •♦^o'e t»me. it appeared that the greater part ot the mineral 



had been difTolved, but the furface of the glafs cover was not 

 in the leaft atTected. 



(8.) Some of the cryOals were introduced into a fmall glafs 

 retort, to which a receiver was adapted. The retort was ex- 

 pofed to the beat of a charcoal fire. A fluid diftilled over into 

 the receiver, which had a peculiar empyrcumalic fmell. It 

 changed Htmus- paper to a faint red. It produced no change 

 in a folutioB of nitrate of filverj but it caufed a white preci- 

 pitate in a folution of nitrate of mercury. I attributed thefe 

 pbaenomena, at the time, to a fmall bit of the feather with 

 which I had fwept the powder into the retort, and which, I 

 thought, had fallen into it. A flight ^Xhilifli cruft was alfo 

 produced in the neck of tl>c retort, but the fmallnefs of the 

 quantity did not admit of examination. 



(9.) Some of this mineral, expofcd to a red heat for about 

 (en minutes, loft in weight at the rate of 25| per cent. Another 

 portion, expofed to a ftronger heat for naore than an hour^ 

 loft 30| per cent. This operation was performed in a crucible 

 of platina ; the cover of which gave fome indications as if a 

 flight portion of the finer parts had boen volatilized. 



Some of the compaft fpecies, after expofure to a red heat 

 for one hour, experienced a diminution in weight of 30 per 

 cent, 



(10.) The fulphuric, muriatic, and nitric acids, aided by 

 a long digefting heat, effeO. nearly a complete folution of 

 this fubftance. The quantity of the undiflblved refiduum is 

 diminiftied in proportion U> the purity of the mineral em- 

 ployed. 



(11.) The nitrate of filver, as well as the muriate of ba- 

 rytes, produce no change in the folution of this fubftance in 

 nitric acid. 



(12.) The folutions of tins fubftance in muriatic and nitric 

 acids, cannot be brought to cryftallize. 



B. 



(1.) I felefted fome of the cryftals of this fubftance, as free 

 as it was poffible from extraneous matter. 50 grains grofsly 

 pounded were expofed, in a platina crucible, to a red heat for 



