Chemical Science. 157 



a pole, generally of birch, is thrust into it, and retained there ; 

 a violent ebullition takes place, which is continued until the 

 refiner perceives, by the assays he takes, that the grain is closed 

 and silky, and the metal of a light red colour. The copper is 

 then laded out into cakes. 



The whole of this operation requires great attention. The 

 surface must be covered with charcoal, or the metal will go 

 back. On the contrary, if the poling be continued too long, 

 the colour becomes a light j^llowish red, and the malleability 

 is injured. In that case, by drawing the charcoal off, and ex- 

 posing the metal to air, it is restored to a proper state. 



Some curious questions arise with regard to the copper in 

 these different states. Is the dry copper combined with oxy- 

 gen? or is there any oxide of copper, either diffused through or 

 combined with the metal? Is the overpoled copper a com- 

 pound with carbon ? Is the malleable metal, copper, in a pure 

 state ? or is the effect of the pole merely mechanical ? It may 

 be remarked, that dry copper has an extraordinary action on 

 the iron tools used ; they become bright, like iron in a smith's 

 forge, and are consumed much more rapidly than when the 

 copper is in a malleable state ; also, that when copper is gone 

 too far, it oxidizes slowly ; on the surface it remains bright, and 

 more than usually splendent, reflecting, like a mirror, every 

 brick in the roof; thus supporting the idea, that carbon is 

 united with it, and, by combining with the oxygen of the air, 

 prevents the formation of oxide. — See Mr. Vivian's paper, Ann, 

 Phil. v. 121. 



On this head we may refer also to Mr. Lucas's experiments 

 on silver. See Journal, Vol. viii. p. 168. 



8. Action of Ammoniacal Gas on Copper. — The following 

 experiments are by Signor Fusinieri : — Dry iron and copper 

 wires were introduced into dry barometer tubes, into which dry 

 ammoniacal gas was then introduced over mercury. Then in- 

 clining the tubes, the part containing the metal was heated by a 

 lump. After a while, the iron became of a brownish colour, and 

 the volume of the gas increased, from the decomposition of the 

 ammonia into its elements ; but no other results were obtained. 



On the contrary, the copper wire gave evident signs of com- 

 bination. The bulk of the gas diminished, notwithstanding a 

 partial decomposition, and consequent expansion. The copper 

 became of a paler colour, and a sublimate rose, and attached 



