on certain Stony and Metalline SubJIances. 221 



tides irregularly (Hifeminatcd next demand examination. 

 I firft examined the pyrites. Their very loofe texture made 

 jt exceedingly difficult to collect the weight of 16 grains, 

 >vhich was however effected by the dexterity of the Count de 

 Bo urn on. 



I digeftcd thefe, at a low heat, with weak muriatic acid ; 

 which acted gradually, and difengaged a trifling but fenlible 

 quantity of fulphureted hydrogen gas. After feveral hours, 

 I found the acid discontinued its action. The whole me- 

 talline part appeared in folution ; but fulphur and earthy 

 particles were obfcrvable. The fulphur, from its fmall fpe- 

 einc gravity, was fufpended through the folution ; whilft 

 the earthy matter, which could not be feparatcd by mecha- 

 nical means, was fortunately left at the bottom of the di- 

 gefting veffel. I decanted off the folution, holding fufpended 

 the fulphur ; and, by repeated warning, feparated every- 

 thing belonging to the pyrites from the infoluble earthy- 

 matter, the fubtraction of which reduced the weight of real 

 pyrites to 14 grains. I next obtained the fulphur, by filtra- 

 tion. When it was as dry as I could make it, without fear 

 of its being fublimed, its weight was two grains. To the 

 filtrated liquor I added nitrate ot barytes, by way of detecting 

 any fulphuric acid which might have been prefent ; but no 

 cloudineis enfued. T then feparated, by fulphate of ammonia, 

 the barytes thus added, and precipitated the iron with am- 

 monia. The liquor, on the fubfidence of oxide of iron, ap- 

 peared of a violet purple colour : it contained nickel, which 

 I threw down with fulphureted hydrogen gas, there being 

 already a fufficient excefs of ammonia in the faline liquor to 

 form an alkaline hydrogenized fulphuret. The oxide of iron, 

 after ignition, weighed 15 grains ; and the fulphuret of 

 nickel, reduced to an oxide, weighed, after the fame treat- 

 ment, fomething more than one grain. The proportions of 

 the fubftances contained in the pyrites of the ftone from Be- 

 nares may therefore be confidered nearly thus : 



Grains. 

 Sulphur - - 2 



Iron ----- - jol 



Since 15 grains of the oxide reprefent about that 

 quantity of iron, 



Nickel, nearly - - I 



Extraneous earthv matter - 2 



It is obfcrvable that, notwith (landing the lofs appears to 

 be only half a grain, it was probably more, becaufe the ful- 

 phur 



