Mr. A. Dick's Contributions to the Metallurgy ofCoppe)'. 415 



The best method of testing copper for oxygen is to heat a 

 strip of it, about as thick as a sixpenny-piece, in a reducing 

 atmosphere for about half an hour, and tlien to try if it still 

 retains its pliancy completely, which it will not do if it contained 

 a notable quantity of oxygen. The diminution of specific gravity 

 produced by the porosity arising from the reduction of the oxide 

 will be afterwards alluded to, when treating of the effect of am- 

 monia on red-hot copper. 



OvERPOLED Copper. — It is generally believed that the brittle- 

 ness of overpoled copper is due to the presence of carbon. In 

 all the specimens which the writer examined, or made by melt- 

 ing tough pitch copper, or commercial wire or sheet in charcoal, 

 lead or antimony, or both, were found. And it was ascertained 

 by experiment, that the addition of these substances to pure 

 copper in the same amount as they existed in overpoled coppei", 

 was sufficient to give to the previously pure copper the brittle- 

 ness of overpoled copper. Various other substances, likely, from 

 the process of manufacture, to occur in overpoled copper, were 

 sought for, and experiments were made to ascertain the effect 

 which they would have by adding them to pure copper. 



Effect of Nitrogen. — This has been supposed to play a part, 

 and it seemed likely to do so, because, according to certain state- 

 ments, the presence of a most minute quantity of it in copper 

 renders it extremely brittle (see English edition of ' Gmelin's 

 Chemistry,' vol. v. p. 444), where the compound is described 

 as " nitride of copper with very great excess of copper." It is 

 said to be made by passing dry ammoniacal gas over red-hot 

 copper wire. According to one statement, the copper increases 

 in weight and diminishes in specific gravity. No such com- 

 pound, however, seems to be formed by this method. It is true 

 that ammonia, passed over red-hot copper wire, renders it ex- 

 tremely brittle ; but this is evidently due to reduction of the 

 suboxide, and not to absorption of nitrogen ; because, if the gas 

 be passed over red-hot copper wire made from electrotype copper, 

 which contains no suboxide, the wire is found to be unaltered. 

 Or if the commercial wire be first melted in hydrogen or under 

 charcoal, so as to reduce the suboxide, then rolled out, and after- 

 wards submitted to the action of ammonia at a red heat, it will 

 be found to remain perfectly unaltered. According to the expe- 

 riments made on this subject by the writer, when the wire lost 

 its pliability by the action of ammonia at a red heat, it was 

 always found to have lost weight and diminished* in specific gra- 

 vity, and water was produced. When the wire did not lose its 

 pliability, it was found to have remained unaltered in weight and 

 also in specific gravity, and no water was produced. 



Tough pitch copper, that is, copper containing suboxide, when 



