[ 442 ] 



LXV. On the Conversion of the Bisulphuret of Copper {Yel- 

 low Copper Ore) into the Sulphuret [Vitreous Copper)' by Elec- 

 tricity. By Mr. Robert Hunt, Secretary to the Royal 

 Cornwall Polytechnic Society *. 



TXAVING been recently engaged in an experimental in- 

 quiry into the electricity of mineral veins, and being de- 

 sirous of examining all the phaenomena which have any bear- 

 ing on this most interesting subject, I have been induced to 

 institute some experiments on the influence of electric cur- 

 rents upon copper pyrites, which is a bisulphuret of copper 

 and iron. 



At the Bristol meeting of the British Association, Robert 

 Were Fox, Esq. exhibited the experiment of the conversion 

 of the bisulphuret of copper into the sulphuret, and in the 

 Fourth Annual Report of the Polytechnic Society (1836), 

 several experiments are detailed in proof of the fact. In re- 

 peating those experiments, having adopted other methods 

 than those pursued by Mr. Fox, I have arrived at irrefragable 

 proofs of the process of decomposition, which alone induces 

 me to add my testimony to the high authority of that gentle- 

 man. 



The original experiment consisted in placing the yellow 

 bisulphuret of copper in a solution of sulphate of copper, di- 

 vided by a wall of clay from a cell containing plain or acidu- 

 lated water, in which was placed a piece of metallic zinc con- 

 nected by a wire with the ore. By this arrangement the ore 

 was in a short time changed, over its surface, into the sul- 

 phuret or vitreous copper, having parted with a portion of its 

 sulphur and its iron. 



1. I was extremely desirous of ascertaining if this change 

 would take place in a solution which did not contain copper. 

 I therefore divided a vessel by a thin wooden partition. In 

 one cell I placed a solution of the sulphate of soda, and in the 

 other water acidulated with sulphuric acid. Into the sulphate 

 of soda I placed a piece of the bisulphuret of copper weighing 

 two hundred and fifty-six grains, connected with a piece of 

 zinc which dipped into the other cell. After three days, the 

 ore having become first iridescent and then gray over its 

 surface, I removed and weighed it. Its weight was now two 

 hundred and forty-seven grains, having lost nine grains. By add- 

 ing ferrocyanate of potash to the solution a considerable por- 

 tion of the cyanate of iron was formed ; a convincing proof of 

 the separation of iron from the ore. 



2. A piece of the copper pyrites, weighing two hundred 



* Communicated by the Author. 



