1 §24.] Copper Pyrites, and Sutyhuret of Bismuth. 355 



mass. In the crystal of analcime which I analyzed, I found a 

 crystal of apophyllite of an inch long. It is sometimes difficult 

 to separate the mass of the analcime from these crystals of 

 apophyllite ; the latter, however, are discovered by their pearly 

 lustre, and especially by their distinct cleavage, which is parallel 

 to the plane perpendicular to the axis. It follows nevertheless 

 from my analysis, in which I could discover neither lime nor 

 potash which occur in apophyllite, that the fragments which I 

 employed were perfectly free from this substance. 



Copper Pyrites. 



There are many analyses of copper pyrites ; but they do not 

 present any probable formula, and differ from each other. I have 

 analyzed three sorts of crystallized copper pyrites, and I found in 

 all of them the same proportions of constituent parts. 



The analysis of copper pyrites, although very simple, never 

 gave me results which corresponded with a probable formula, 

 when I separated the oxide of iron from the oxide of copper by 

 pure ammonia. The oxide of iron precipitated always contained, 

 even after having been perfectly washed, a considerable quantity 

 of oxide of copper, which I could not separate if I did not preci- 

 pitate the copper from the muriatic solution of oxide of iron by 

 means of sulphuretted hydrogen. 



I dissolved in each analysis of copper pyrites, two different 

 quantities in aqua regia. I precipitated one of the solutions by 

 muriate of baryles to determine the quantity of sulphur by the 

 sulphate of barytes obtained, and I poured into the other pure 

 ammonia in excess. The oxide of iron precipitated was heated 

 to redness, and dissolved in muriatic acid, which always left a 

 small quantity of silica. I then treated, as already mentioned, 

 the solution with sulphuretted hydrogen. 



I obtained the following results from two varieties of crystal- 

 lized copper pyrites from Ramberg, in Sayn, and from Fursten- 

 berg : 



Ramberg. Furstenberg. 



Copper 34-40 33-12 



lion 30-47 30-00 



Sulphur 35-87 30-52 



Silica 0-27 0-30 



101-01 100-03 



The analysis of the crystallized copper pyrites from Freiberg, 

 gave no similar results. 



Sulphwet of Bismuth. 



This sulphuret from Riddarhyttan, in Sweden, I found to 

 possess the same composition as the artificial sulpluuet of 

 bismuth ; namely, 



2 a 2 



