from the Iron Pyrites occurring near BrocJcville. 195 



verted into cobalt oxide. At a later stage of the operation, part 

 of the sulphurous acid formed comes in contact with the peroxide 

 of iron, and is, through its agency, further oxidized into sulphuric 

 acid, which combines with the iron oxide, forming finally a com- 

 paratively small quantity of sulphate of peroxide of iron. The 

 cobalt oxide also combines with sulphuric acid, forming sulphate 

 of protoxide of cobalt. These sulphates react on the common 

 salt, producing sulphate of soda, with perchloride of iron and 

 protochloride of cobalt. Air having still access, the perchloride of 

 iron is resolved into peroxide of iron and chlorine gas, which es- 

 capes and may be recognized by its odour, so soon as the evolu- 

 tion of sulphurous acid has ceased. Protochloride of cobalt is also 

 decomposable by heating in a current of air, the products being 

 chlorine and cobalt oxide ; but this change does not take place 

 until the perchloride of iron has been wholly decomposed. It is 

 at this point that the calcination must be interrupted; that is, as 

 soon as the perchloride of iron is decomposed, but before the 

 decomposition of the protochloride of cobalt commences. When 

 the operation is stopped exactly at this point, the calcined resi- 

 due yields with water a solution containing no iron oxide, or but 

 a trace, and the whole of the cobalt in the state of protochloride. 

 I have made many trials of the above process with the Brock" 

 ville pyrites, all yielding results confirmatory of the above reac- 

 tions. Tho following are among the most conclusive of them : 

 1000 grains of the ore were calcined as above described, with 100 

 grains of common salt in a common muffle furnace. The mate- 

 rials were withdrawn from the muflfle, as soon as strong and pure 

 chlorine commenced to be evolved, and the evolution of chlorine 

 continued until the materials were cooled to a certain point. The 

 calcined residue weighed 780 grains, and contained in 100 parts, 



Peroxide of iron 85.300. 



Sulphate of soda 5.700 = 1.28 sulphur. 



Protochloride of cobalt, . . 1.343 = 0.775 cobalt oxide. 



Protochloride of copper.. 0.327 = 0.193 cupric oxide. 



Perchloride of iron 0.059 = 0.029 ferric oxide. 



Chloride of sodium 7,271 by difference. 



100.000 

 The five last mentioned constituents were of course soluble in 

 water. According to these results, the 780 grains of residue must 

 have contained six grains of cobalt oxide ; consequently 0.60 per 

 cent, of this substance had been extracted from the pyrites. The 



