Conversion ofBisulphuret of Copper into Sulphur et. 443 



grains, was placed in a solution of the muriate of barytes, water 

 only being in the cell containing the zinc with which the ore 

 was connected. In a few days the ore was covered with a 

 reddish-brown powder, which was proved to be peroxide of 

 iron, beneath which was a coating of vitreous copper. A 

 quantity of the sulphate of barytes was formed and collected, 

 and traces of copper were evident, in the solution. During 

 the process there was a steady liberation of gas from the fluid 

 in contact with the copper ore, which was collected and found 

 to be pure hydrogen. This experiment proves that the sul- 

 phur liberated from the yellow ore is converted into sulphuric 

 acid at the expense of the oxygen of the water, which is seized 

 by the barytes and forms the sulphate of that earth, and that 

 the iron is freed in the state of peroxide. It is possible the 

 copper detected in this instance may have arisen from the wire 

 used to make the connexion. The water in the cell which 

 contained the zinc was now found, as was of course expect- 

 ed, to hold muriate of zinc in solution. From the adhesion 

 of the peroxide of iron to the piece of ore, it was difficult to 

 ascertain the actual loss of weight it had suffered. 



3. Two pieces of copper pyrites, each weighing seventy-two 

 grains, were connected by zinc wires with a single pair of 

 zinc and copper plates excited by acidulated water, and both 

 plunged into a solution of the muriate of soda. The zinc 

 wires were so quickly destroyed from the action of the electro- 

 negative ore on the positive metal, that it was found impossible 

 to carry on the experiment for any time. The change was, 

 however, well marked even in this case. 



4. Seventy-four grains of copper pyrites was connected by 

 silver wire, with the positive pole of a circular battery of a 

 single pair excited with salt and water, and fifty-two grains 

 of the same ore with the negative pole in like manner. These 

 two pieces were placed in a precipitating glass filled with a 

 solution of the muriate of barytes. It will be evident, that 

 in this experiment the fragments of ore form the poles of a 

 galvanic arrangement. In forty-eight hours they were ^re- 

 moved ; it was now found that one piece weighed seventy-five 

 grains, and the other only fifty, the latter being partially 

 changed into vitreous ore, while the former was covered with 

 specks of the peroxide of iron. It was extremely interesting 

 to find the peroxide acting as an acid would have done, and 

 passing to the positive pole. Rather more than a grain of 

 sulphate of barytes was collected from the glass ; and the so- 

 lution on being treated with the ferrocyanate of potash gave 

 a precipitate of the cyanate of copper: copper in minute quan- 

 tity was also detected by means of a piece of polished iron. 



