SUBOXIDE OF COPPER. 



With the exception of titanium, copper is the only metal of a 

 red colour. The crystals of native copper, and of that obtained 

 in the humid way by precipitation with iron, belong to the 

 regular system ; but the crystals which form in the cooling of 

 melted copper were found by Seebeck to be rhomboidal, and to 

 have a different place in the thermo-electric series from the 

 other crystals. The density of copper when cast is about 8.83, 

 and when laminated or forged 8.95 (Berzelius.) It is less fusible 

 than silver, but more so than gold, its point of fusion being 

 1996 (Daniell.) It is one of the most highly malleable metals, 

 and in tenacity is only inferior to iron. It has much less affinity 

 for oxygen than iron, and decomposes water only at a bright red 

 heat, and to a small extent. In damp air, it acquires a green 

 coating of subcarbonate of copper, and its oxidation is remark- 

 ably promoted by the presence of acids. The weaker acids, 

 such as acetic, have no effect upon copper, unless with the 

 concurrence of the oxygen of the air, when the copper rapidly 

 combines with that oxygen, and a salt of the acid is formed. 

 Copper scarcely decomposes the hydrated acids, by displacing 

 hydrogen ; for when boiled in hydrochloric acid, it disengages 

 only the smallest traces of that gas. But hydrogen does not 

 precipitate metallic copper from solution. Copper acts violently 

 on nitric acid, occasioning its decomposition, with evolution of 

 nitric oxide, and dissolving as a nitrate. 



Suboxide of copper, Red oxide of copper, Cu^O; 891.4 or 

 71.42. This degree of oxidation is better marked in copper 

 than in any other metal of the magnesian class. The suboxide 

 of copper is found native in octohedral crystals, and may be 

 prepared artificially by heating to redness, in a covered crucible, 

 a mixture of five parts of the black oxide of copper with four 

 parts of copper filings. It is a reddish brown powder, which 

 undergoes no change in the air. The surface of vessels of 

 polished copper is often converted into suboxide, or bronzed, to 

 enable them to resist the action of air and moisture : this is 

 done by covering them with a paste of peroxide of iron, heating 

 to a certain point, and afterwards cleaning them, to remove the 

 oxide of iron ; or otherwise, by means of a boiling solution of 

 acetate of copper. 



Dilute acids decompose suboxide of copper, dissolving the 

 protoxide, and leaving metallic copper. Undiluted hydrochloric 

 acid dissolves the suboxide, without decompofition, or rather 



