Analysis of the Copper Ore of Franco aia, 



ascertained by the masterly and accurate analysis of Mi 

 Hatchett." It is evident that the sesquisulphuret may be 

 considered as a compound of one atom of the sulphuret, and 

 one atom of the bisulphuret. There are also several com- 

 pounds of sulphur and copper, and different views have been 

 entertained of their constitution by different chemists, which 

 depend on the adoption of the number 3i, or of 64, as repre- 

 senting the atomic weight of copper on the hydrogene scale. 

 Taking with Wollaston, Thompson, and others, the number 

 32, as the equivalent number of copper, the three sulphurets 

 of that metal will be constituted as follows :f 



1. Disulphuret of copper, containing- 2 atoms of copper -}- 1 atom of sulph. 



2. Sulphuret of copper, do. 1 do. 1 do. 



3. Bisulphuret of copper, do. 1 do. 2 do. 



The first compound is the sulphuret of copper, or copper 

 glance of mineralogists ; the latter is a product of art ; the 

 second has not been formed artificially, but exists in the va- 

 riety of pyritous copper, analysed by Mr. Rose; a variety 

 which he has shown to contain copper, sulphur and iron, in 

 such proportions as to form one atom of the sulphuret of 

 iron, and one atom of the sulphuret of copper above named. 

 The variable proportions of the constituents of pyritous cop- 

 per, which accurate chemical analysis proves to exist in dif- 

 ferent specimens of the ore, will not permit us to consider 

 them as possessing the same atomic constitution, as that which 

 was the subject of the experiments of Mr. Rose. My atten- 

 tion has recentty been called to this subject, in consequence 

 of the observations of Dr. Thomson on sesquisulphuret of 

 iron, and I submit to the Lyceum, the results of a careful 



* Phil. Trans. 1801, 



| F:rst. Princ. p. ID9. ^ ^ ol. II. 



