Analysis of the Copper Ore of Franconia. 2bl 



+ one atom of iron, + two and a half atoms of sulphur, or 

 should contain in 100 parts, 



By theory. And we have by experiment, 



Copper - - 32 - - - - 31.95 



Iron, - - 28 - - - - 28.20 



Sulphur, - - 40 - - - - 39.85 



100 100.00 



The slight differences presented between the experimental 

 results and theoretical composition, are, no doubt, to be as- 

 cribed to unavoidable errors of manipulation, and we may 

 conclude, therefore, that the specimen of the Franconia ore 

 which was the subject of experiment, is composed of, 



One atom of sulphuret of copper -f- one atom of sesquisul- 

 phuret of iron. 



An attempt was made at the time the analysis was perform- 

 ed, to reduce the composition to an atomic expression, but 

 being unacquainted with the sesquisulphuret of iron, at that 

 period, I was unable to do it. 



It appears highly probable that there are, at least, two 

 distinct species of copper pyrites, which have always been 

 confounded with each other, viz. a pyritous copper consist- 

 ing of, 



Sulphuret of copper, 1 atom = 48 



Sulphuret of iron, 1 atom = 44, analyzed 



by Mr. Rose, and the ore of Franconia consisting of, 

 Sulphuret of copper, 1 atom = 48. 



Sesquisulphuret of iron, 1 atom = 52. 



One of these varieties contains 40 per cent, of sulphur, and 

 the other 34.78. Notwithstanding the difference in the com- 



