<X) ON STONY AND METALLINE SUBSTANCES 



well as, I prefume, other bodies, (landing in the order of affi- 

 nities before ammonia, decompofe the fait; but the nickel is 

 then continued in folution by the difengaged ammonia. 



alwa t Yx'amTned As lt may be irna S ined that l have occafionally met with 

 to detedV copper copper, when I defcribe a violet or purple ammoniacal folu- 

 if it had been tion, it is right to obferve, that to avoid this error, I have 

 either reduced the liquor to a neutral ftate, and endeavoured, 

 without tuccefs, to obtain from it a precipitate, with a folution 

 of fulphureted hidrogen gas ; or, by adding an acid to flight 

 excels, and immerfing a piece of iron, I have not been able 

 to dete<5t a trace of copper. Thefe, and many other trials, 

 when they do not appear to be made before the eftimation of 

 the quantities of nickel, have been conftantly made after- 

 wards. 

 The coating g ut to return to the incruflation or coating of the ftonc, 



contained iron .. ° 



nearlv metallic, * ne decompoution ot the nitric acid ihewed the pretence of 



and fome nickel, matter at leaft nearly metallic, although not attractable ; and 

 the examinations made of the liquor, from which the iron was 

 precipitated, afcertained the prefence of nickel beyond dif- 

 pute. The difficult)' of obtaining the coating of the ftone, ei- 

 ther diftinct from matter not belonging to it, or in fufficient 

 quantity, induced me to relinquifli the idea of attempting to 

 give the proportions of its conftituent parts. 

 The toning The ftone being deprived of its covering, the mining par- 



ftone** ' C nicies irregularly diffeminated, next demand examination. I 

 firft examined the pyrites. Their very loofe texture made it 

 exceedingly difficult to collect the weight of 16 grains, which 

 was however effected by the dexterity of the Count de 

 Bo urn on. 

 •were digefted in 1 digefted thefe, at a low heat, with weak muriatic acid ; 

 add* 6 muriatl ° which a&ed gradually, and difengaged a trifling but fenfible 

 quantity of fulphureted hidrogen gas. After feveral hours, I 

 found the acid difcontinued its action. The whole metalline 

 It diflblved the part appeared in folution ; but fulphur and earthy particles 

 "endtd'tht fut were obfervable. The fulphur, from its fmall fpecific gravity, 

 phur, and the was fufpended through the folution ; whilft the earthy matter, 

 f^f 1 / a ™ 01 * which could not be feparated by mechanical means, was for- 

 tunately left at the bottom of the digefting veffel. I decanted 

 off the folution; holding fufpended the fulphur; and, by re- 

 peated warning, feparated every thing belonging to the py- 

 rites 



