Jottings on Copper. 69 



Having thus briefly adverted to the effect of oxygen on 

 copper, we must select, from various important combinations, 

 those which are alleged to take place with carbon, and which 

 are known to occur with silicon and phosphorus. Let us com- 

 mence with carbon, which was presumed to be chemically com- 

 bined with copper during the process of poling, and to give rise 

 to the brittleness of what is called " overpoled copper." These 

 terms will be understood when it is explained that one of the 

 processes of copper-melting consists in plunging a thick pole of 

 oak or birch, in a green state, into melted metal which contains 

 a good deal of dioxide ; anthracite, or " pure free-burning coal, 

 being previously thrown on the surface. The wood in contact 

 with the copper is rapidly decomposed, much gas and vapour 

 are evolved, which cause the metal to be splashedabout,and every 

 part of it to be exposed to the reducing action of the coal upon 

 its surface." The chief effect of this process is that of deoxidar 

 tion ; but it obviously provides conditions under which coppe- 

 and carbon might unite, if their chemical affinities so decide. 

 When the poling is carried on to the proper extent, the copper 

 becomes tough by the removal of the superfluous oxygen. If, 

 however, it is carried on too long, it is made brittle, in accord- 

 ance with what has been stated of the use of a small quantity 

 of dioxide in copper that is impure. Dr. Percy requested Mr. 

 Dick to make a number of experiments to ascertain what action 

 the carbon exerted, and although their results do not justify the 

 assertion that small quantities of carbon may not combine with 

 the copper and affect its properties, he ascertained that " com- 

 paratively pure copper is not rendered brittle by being heated 

 or melted in contact with comparatively pure charcoal." 



If copper is heated to whiteness in contact with silica and 

 carbon, a compound is obtained which resembles gun-metal in 

 colour, and is tough and much harder than copper. It may be 

 rolled or hammered out while cold, but cracks under such treat- 

 ment at a red heat. A proportion of 1*82 per cent, of silicon 

 gives an alloy tougher than gun-metal, and probably adapted 

 to manufacturing use. Much larger proportions induce brittle- 

 ness. A still more interesting compound is obtained by drop- 

 ping phosphorus — which should be covered with an electrotype 

 coating of copper — into the metal in a melted state. In the 

 Laboratory at Woolwich many experiments were made, of this 

 nature, with a view to obtain a material adapted to the manu- 

 facture of rifled guns; but the improved modes of working 

 iron, employed by Armstrong or Whitworth, threw them into 

 the shade, as far as this special object was concerned. The 

 quality of this compound varies with the proportion of phos- 

 phorus ; 11 per cent, giving great hardness, but rendering the 

 metal brittle. Perhaps the most interesting feature of the 



