TREATMENT OF ORES. 255 



first submitted to a preliminary oxidisation by means of ozone. 

 After oxidisation and lixiviation, the silver was deposited 

 from the solution by electrical precipitation. The gold and 

 silver remaining in the deposit were submitted to amalgama- 

 tion. The latter was facilitated by wetting the ore with a 

 solution of caustic alkali, and by connecting the stirring appara- 

 tus of the amalgamating vessel to the negative pole of a battery 

 having its positive pole connected to the vessel itself. Werder- 

 mann has also described a process which consisted in roasting 

 the ore in a current of vapours of sodic chloride, of air, and 

 oxygen at the same time. The chlorides formed were dissolved 

 by electricity. 



CoUeys Method. The sulphuretted ores, and especially 

 copper ores, are roasted so as to obtain sulphate of copper, 

 which is dissolved in water ; the iron is precipitated by 

 means of lime, and the solution submitted to electrolysis. 

 In order to prevent the polarisation due to the liberation of 

 oxygen on the insoluble anode, the inventor proposes to send 

 into the bath a current of sulphurous acid generated by the 

 roasting. The acid combines with the oxygen and there is a 

 production of sulphuric acid, which remains dissolved. 



We cannot recommend processes so summarily described by 

 their inventors ; we only insert them here in order to direct 

 young experimenters, and prevent them wasting their time 

 upon methods already unsuccessfully attempted by their pre-. 

 decessors. 



TRIAL OF THE TREATMENT OF ARGENTIFEROUS COPPER 

 ORES. We will record an interesting trial made in Japan in 

 1882, on argentiferous ores. The operation was conducted 

 with the solution of double chloride of silver and sodium. 



The solution was placed in two glass vessels connected by a 

 tube, the extremities of which lined with a linen cloth did not 

 allow of the passage of any solid particle. 



Two electrodes of platinum wire were next introduced in the 

 vessels. The chlorine, which is rendered free by the decom- 

 position of the dissolved chloride, attacks the copper of the 

 pyrite, giving off cupric chloride, iron perchloride, as well as 

 sulphate of copper and of iron. 



