from the Iron Pyrites occurring near BrocJcville. 1 97 



sulphuric acid, than when the pyrites was calcined with salt 

 alone. 



Having thus explained the rationale of the process, I proceed 

 to touch upon its application on the large scale. It will be seen 

 from the above experiments that only a very small proportion of 

 the sulphur contained in the pyrites, is necessary for the extrac- 

 tion of the cobalt. There would be abundance of it left in the 

 pyrites for this purpose, even although it were previously roasted 

 in pieces of about the size of an egg. It has been found that the 

 residue from the burning of pyrites in lumps, in the manufacture 

 of sulphuric acid, contains six or seven per cent, of sulphur,* and 

 this would also be the case with the Brockville pyrites, if roasted 

 in heaps or shaft furnaces. A previous roasting would be of 

 advantage, because it would lessen the cost of the subsequent 

 calcination, render the pyrites more easily stamped to powder, 

 and admit of the manufacture of sulphuric acid from the sulphur- 

 ous acid evolved. After roasting, the pyrites is reduced to pow- 

 der, and mixed with the salt. The mixture is then brought on 

 to the hearth of a common calcining reverberatv->ry furnace, heated 

 to low redness, raked about, and tested from time to time. 

 So soon as pure chlorine is evolved, and the mass ceases to glow 

 in the furnace, and gives with water a solution containing little or 

 no iron, the mixture is withdrawn from the furnace. When cool, 

 it is brought into a large tub, where it is stirred up with hot 

 water. If the calcination has been properly performed, a solution 

 is obtained having a beautiful rose colour. This is drawn off, or 

 if necessary filtered from the insoluble residue of peroxide of iron 

 which is washed with fresh quantities of water until it no longer 

 yields a solution containing cobalt The more dilute solutions 

 thus obtained, are used for treating fresh quantities of the cal- 

 oined material. The rose-coloured solution contains besides the 

 oobalt, a small quantity of copper, and a trace of iron, together 

 with whatever sulphate of soda has been formed, and the com- 

 mon salt which may have been left undecomj^osed. The copper 

 and iron may be separated from the solution by adding a slight 

 quantity of a dilute solution of carbonate cf soda. They are pre- 

 cipitated as carbonates, before the cobalt, and are separated from 

 the solution by filtration. The filtrate is then treated with a 

 further quantity of a solution of carbonate of soda, more con- 



• Fabriques de produits chimiques. Rapport a M. le Ministre de I'ln- 

 terieur, par la Commission d'enquete. Bruxelles, 1856. 



