TRKATMKNT OK OIII 249 



especially when the ores are not separated by a resisting dia- 

 phragm ; in the case of the linen bag the action is immediate. 



"I have successively operated on two qualities of ores. 

 The first one was a cupriferous iron pyrite containing 4 '60 

 per cent, of copper, and in which the yellow copper pyrite 

 with the iron pyrite forms a very homogeneous mass. In the 

 second ore the cuprous pyrite formed little agglomerations or 

 spots disseminated in the mass ; the percentage was 3 60 per 

 cent, of copper. 



" After a few days' action of the battery, a notable proportion 

 of the two ores was attacked, and the copper resulting from it 

 was partially deposited on the negative electrode. But the 

 attack, as I had anticipated, was attended with different results 

 on the two ores. The first one, of homogeneous composition, had 

 had all its elements parallelly dissolved, so that the residue 

 still gave 4*57 per cent, of copper ; the second ore, contrarily, 

 only contained 2 35 per cent, of copper after the attack. The 

 combination of cuprous pyrite with the iron pyrite had, there- 

 fore, been dissolved in a greater proportion than the martial 

 pyrite. 



Bias and Miest. In a note published in 1882, M. Bias, 

 Professor at the Lou vain University, and M. Miest, Engineer, 

 made known a process for the treatment of sulphuretted ores, 

 which is not absolutely new, but has the merit of being well 

 presented. 



" Our method," say the authors, " is based upon the following 

 facts : 



" 1st. The natural metallic sulphides are in certain degrees 

 conductors of the galvanic current ; 



" 2nd. The sulphuretted ores (mixtures of sulphides and 

 gangues) are conductors of the current, even when the proportion 

 of gangues is very large. 



" 3rd. If a solution of a salt, the acid of which attacks the 

 natural sulphides, is electrolysed, by using the latter as anodes 

 the metal of the sulphide is dissolved, whereas the sulphur 

 remains deposited on the anode. It is with the nitrates that 

 this operation is more easily conducted, and, in that case, 

 without the formation of sulphate." 



