418 Mr. A. Dick's Contributions to the Metallurgy of Copper. 



was then allowed to go out gradually, so that the metal had the 

 opportunity of absorbing carbon at all intermediate temperatures 

 in very favourable circumstances, being surrounded on all sides 

 by charcoal. It was reiuelted under similar conditions, and the 

 lump so obtained was sent, along with the small ingot, to Mr. 

 David Forbes at Birmingham, who was kind enough to get them 

 rolled into sheet and drawn into wire. No mention was made 

 of the object of the experiment, but it was requested that they 

 might be treated like ordinary copper, and that the men super- 

 intending the rolling mill would give an opinion on the working 

 qualities of the metal. When the wire and sheet were returned, 

 it was said, that although the casting was not good, yet the metal 

 was tit for any work. It would seem from these experiments, 

 then, that the amount of carbon in the copper did not render it 

 brittle, and the opportunities afforded to the metal to absorb 

 carbon were far greater than it has during the short period 

 which elapses between the time when the copper is at the tough 

 pitch till that at which it is at the overpoled state in the retining 

 process ; so that it is proved that the brittleuess of overpoled 

 copper is not due to carbon. A very marked effect of carbon 

 on an ingot cast in the ordinary manner will be referred to after- 

 wards. Whether the carbon present in overpoled copper increases 

 the injurious effect exerted upon the malleability of the metal by 

 the foreign metals always present, has scarcely been inquired into ; 

 because if tough pitch copper — which, as it contains oxide, cannot 

 contain carbon — be melted in hydrogen, it becomes brittle, just 

 as it does if melted under charcoal ; and any difference in the 

 degree of brittleuess requires more experience than the writer is 

 possessed of to detect. 



A great many experiments were made for the purpx)se of de- 

 termining whether carbon actually is present in copper which 

 has been melted under charcoal. Of these the most conclusive 

 will be given, from which it will be seen that the question is 

 not yet definitely settled. Electrotype copper was melted under 

 charcoal and afterwards rolled out. The sheet, after having been 

 cleaned by nitric acid and boiling in solution of caustic potash, 

 was dissolved in perchloride of iron. The solution was left at 

 rest for a day or two so as to deposit a small quantity of sus- 

 pended matter, which was washed by decantation. When dry, 

 it had a dark bluish-gray colour. It was mixed with a little 

 recently ignited litharge, and the mixture was heated in a small 

 tube. Several small globules of malleable metallic lead were 

 produced. As the substance supposed to be, or at least to contain 

 carbon, had not been previously tested for disulphide of copper, 

 which, had it been present, would have i-educed some of the oxide 

 of lead, this experiment alone cannot be regarded as conclusive. 



