68 Jottings on Copper. 



proaches the melting-point, which, lies between those of gold 

 and silver, " it becomes so brittle that it may be readily reduced 

 to powder by trituration, " and workmen in foundries avail 

 themselves of this property when ingots have to be broken up. 

 It is customary to judge of the quality of the copper from the 

 fracture thus produced. This is, however, a very inadequate 

 test ; and Dr. Percy relates an instance of a large quantity of 

 copper being rejected at one of the dockyards on account of the 

 appearance of its fracture, and which was afterwards accepted 

 when it had been remelted and "laded" at a different tem- 

 perature. "We shall presently have something more to say on 

 the peculiarities of naval mismanagement in reference to copper 

 sheathing, but must first allude to the action of oxygen and 

 other substances in affecting the quality of the metal in its 

 various states. 



There are probably three oxides of copper, of which only two 

 are considered by Dr. Percy to concern the metallurgist : one the 

 protoxide, consisting of one equivalent of copper and one of 

 oxygen (Cu 2 0), which is the basis of the ordinary salts of the 

 metal. The other is the dioxide, consisting of two equivalents 

 of copper and one of oxygen (Cu 2 0). This is the red oxide, but 

 Dr. Percy says it constitutes a principal portion of the dark- 

 coloured scale formed when the metal is heated to redness with 

 access of air, and we shall find it has an important action in the 

 various processes to which the metal is subjected, in order to 

 fit it for the uses of man. In a state of fusion, copper is able 

 to dissolve this oxide ; and when it is present in considerable 

 quantities, the metal is brittle, whether hot or cold, and is 

 technically designated, by the smelters, " dry." Eather more 

 than one per cent, of dioxide is stated on the authority of Karsten 

 to render pure copper incapable of being worked in ordinary 

 temperatures without splitting into laminae, and cracking it at 

 the edges. Ordinary copper, however, which contains lead and 

 other impurities, actually requires a certain portion of the 

 dioxide to make it tough and malleable ; and if the oxygen be 

 removed by exposing " tough copper," in the state of wire or 

 foil, to the action of dry hydrogen at a red heat, the metal 

 becomes so brittle that it cannot be bent without breaking. 

 Unfortunately, very little is known concerning the nature of 

 this curious action of the dioxide, or of the proportion it should 

 bear to other impurities in order to afford the best result. The 

 copper annually wasted in the dockyards, for want of this and 

 some other technical knowledge, is worth an enormous sum ; 

 but no government has hitherto exhibited enough intelligence 

 to pay the comparatively insignificant cost of a set of experi- 

 ments by which many intricate questions connected with the 

 metallurgy of copper might be set at rest. 



