222 Experiments and Ohfervahons 



phur could not be reduced to the fame ftate of drynefs in 

 which it exifttd when in combination with the iron ; not to 

 lay that it was, in a fmall degree, volatilized with the hy- 

 drogen gas difengaged during the folution. 



The weight of nickel is a mere estimation. We are not 

 yet fufficiently acquainted with that metal to fpeak of it with 

 accuracy, except as to its prefence. Upon the whole, how- 

 ever, it may be concluded, that thefe pyrites are of a very 

 particular nature ; for, although Henker has obferved that 

 fulphur may be feparated from pyrites by jfturiatic acid, it is 

 by no means the ufual habitude of pyrites to be of fuch eafy 

 decompofition. 



The other fhining particles immediately feen, when the 

 internal ftruclure of the ftone is expofed, are the malleable 

 iron. Before I ftate the examination of this iron, I muft 

 remark, that preliminary experiments having fhown me it 

 contained nickel, I treated feveral kinds of the moft pure 

 irons I could obtain, with nitric acid ; and precipitated the 

 oxide from the metallic fait, by ammonia. The quantity of 

 oxide I obtained from ioo grains of iron was from 344 to 

 146. I may confequently infer, that 100 grains of pure iron 

 acquire, by fuch a procefs, 45 grains of oxygen ; and that, 

 whenever a metallic fubftance, fuppofed to be iron, does 

 not, under the fame circumftances, acquire the fame pro- 

 portionate weight, fomething is either volatilized, or left in 

 folution. Hence, when a metallic alloy of nickel and iron 

 prefents itfelf, a judgment may, at leaft, be formed of the 

 quantity of nickel, by the deficiency of weight in the preci- 

 pitated oxide of iron. 



This mode of treatment was not allowed me in the exami- 

 nation of the coating of the ftone, becaufe it was impoflible 

 to know in what ftate of oxidizement the iron exifted. But, 

 as the particles difleminated through the wnole mafs are 

 clearly metallic, a verv tolerable idea of the quantities of 

 nickel contained in them will be obtained, by noting the 

 quantity of oxide of iron feparated, as above deferibed. 

 05 grains of thefe metallic particles were therefore heated 

 with a quantity of nitric acid, much more than fuftieient to 

 diflblve the whole. Some earthy matter, which, as in a 

 former cafe, was not feparable by mechanical means, re- 

 mained after a complete folution of the metal had been 

 effected. This earthy matter, after being ignited, weighed 

 two grains. The real matter of the prefent examination 

 was therefore reduced to 23 grains, and was in complete fo- 

 lution. I added ammonia to a very fenfible excefs. The 

 oxide of iron was thereby precipitated, ami, being collected 



and 



