416 Mr. A. Dick's Contributioiis to the Metallurgy of Coppen^ 



submitted to the action of ammouiaj or indeed ^wy reducing gas 

 at a red heatj is altered in appearance on the surface, owing to 

 the shght porosity produced. If the surface was previously 

 polished, it becomes dull. If the experiment is continued long 

 enough to reduce the suboxide in the centre of the piece of metal 

 operated upon, it may afterwards be completely reduced to powder 

 by rubbing it gently in a mortar ; but if the action of the gas 

 has not extended to the centre, a core of tough metal remains, 

 from which the altered portion cracks off by bending the piece 

 of metal backwards and forwards. It is curious that the copper 

 containing suboxide is rendered more brittle by ammonia than 

 by anv other reducing gas which has been tried ; but that the 

 change arises simply from reduction of the suboxide seems proved 

 by the fact, that copper containing no suboxide is not altered by 

 heating in ammonia. No quantitative experiments were made 

 to ascertain exactly whether every trace of suboxide is reduced by 

 heating the wire in ammonia, which seems probable, because the 

 wire, as has been said, is rendered still less pliant than when 

 heated in hydrogen for a similar period. The specific gravity of 

 the wire B was found to have diminished by heating in ammonia 

 from 8733 to 8-64.. 



Effect of Silicon. — Berzclius seems to have been thefirst to show 

 that when a mixture of finely divided coppei-, silica, and charcoal 

 is strongly heated, a combination of copper and silicon is obtained 

 (see English edition of ' Gmelin's Chemistry,' vol. v. p. 464). It 

 seemed, therefore, not unlikely that overpoled copper might con- 

 tain some silicon, because carbonaceous and sihceous matters are 

 in contact with it when in the furnace at the overpoled state, 

 and that it might owe some of its properties to the silicon which 

 it contained. It was accordingly sought for by dissolving over- 

 poled copper in nitric acid, evaporating the solution to dryness, 

 and heating the residue till the nitrate of copper was decomposed. 

 The oxide, on being dissolved in hydrochloric acid, left no silica. 

 A tW experiments were, howevei-, made to ascertain the proper- 

 ties "of the compound more fully than seems to have been done, 

 and to see whether it was fitted for any practical purposes. 

 It resembles bronze in appearance, but has a pink tinge, which 

 bronze has not. It is harder than copper, and, at least in cer- 

 tain proportions, tougher than bronze. One specimen, which 

 was found by analysis to contain 1'82 per cent, of silicon, had 

 the specific gravity of 8" 70. It could be hammered and rolled 

 out when cold, -but cracked immediately when hammered at a 

 dull red heat. It was hardened by hammering, and softened 

 again by annealing. When "dipped" in nitric acid it became 

 black, but could be dipped so as to retain its original colour by 

 mixing some hydrofluoric acid with the nitric acid, A medallion 



