Chemical elements
    Physical Properties
    Chemical Properties
    Cuprous Compounds
      Cuprous hydride
      Cuprous fluoride
      Cuprous chloride
      Cuprous bromide
      Cuprous iodide
      Copper suboxide
      Cuprous oxide
      Cuprous hydroxide
      Cuprous sulphide
      Cuprous sulphite
      Cuprous sulphate
      Cuprous selenide
      Cuprous telluride
      Cuprous nitride
      Cuprous phosphide
      Cuprous arsenides
      Cuprous carbide
      Cuprous acetylide
      Cuprous carbonate
      Cuprous cyanide
      Cuprous thiocyanate
      Cuprous silicide
      Cuprous silicofluoride
      Ammonio-cuprous Derivatives
      Carbonyl cuprous sulphate
    Complex Copper Compounds
    Cupric Compounds
    PDB 1a2v-1bxu
    PDB 1bxv-1fwx
    PDB 1g3d-1j9t
    PDB 1jcv-1mfm
    PDB 1mg2-1paz
    PDB 1pcs-1sii
    PDB 1sjm-1w6w
    PDB 1w77-2afn
    PDB 2ahk-2dv6
    PDB 2dws-2ggp
    PDB 2ghz-2mta
    PDB 2nrd-2vm3
    PDB 2vm4-2yah
    PDB 2yam-3bkt
    PDB 3bqv-3fyi
    PDB 3g5w-3mie
    PDB 3mif-3t6v
    PDB 3t6w-9pcy

Cuprous oxide, Cu2O

This Cuprous oxide, Cu2O, occurs as the mineral cuprite or ruby copper. It is formed by reduction of alkaline solutions of complex cupric salts with a reducing sugar, such as dextrose, an example being the reduction of Fehling's solution, the oxide being deposited as a red, crystalline powder.

Cuprous oxide is produced in the form of an orange-yellow, amorphous gel containing water by the reduction of an alkaline cupric solution with sodium hyposulphite:

2CuO + Na2S2O4 + 2NaOH = Cu2O + 2Na2SO3 + H2O.

A better method is the action of hydroxylamine on a cupric salt in presence of alkali. The initial light-yellow product is probably a hydroxide. In absence of air, the colour quickly changes to orange or brick-red, the phenomenon being probably due to elimination of water. The dry product contains 2 to 3 per cent, of water, but above low red heat this water is expelled, the metastable, yellow, amorphous oxide becoming transformed into the stable, red, crystalline variety.

Other methods of formation are the addition of sodium carbonate to a solution of cupric sulphate and sodium chloride reduced with sulphurous acid, and that of an alkaline solution of sodium potassium tartrate to a solution of cuprous chloride and sodium chloride. At temperatures below 350° C. copper reacts with nitrous oxide to form cuprous oxide; above this temperature the product is cupric oxide. Cuprous oxide is also formed at the anode in the electrolysis of a solution of cupric sulphate,12 and by heating cupric oxide in steam.

The oxide crystallizes in cubic octahedra, melting above 1230° C. according to Truthe, and at 1235° C. under a pressure of 0.6 mm. according to Roberts and Hastings Smyth, and of density 5.75 to 6.09. Its solubility in water is very slight, but it dissolves readily in aqueous solutions of ammonia, less readily in potassium hydroxide, and easily in hydrogen halides, with formation of complex derivatives. The solutions absorb oxygen, yielding cupric compounds. When heated in air, the oxide is stable only between 1025° and 1070° C. At 155° C. reduction of the oxide to metallic copper by hydrogen becomes perceptible, the velocity of the reaction increasing rapidly with rise of temperature. It is much accelerated by the presence of a dehydrating agent, such as barium monoxide. At 250° C. the oxide is converted by a solution of chlorine in carbon tetrachloride into a dark-brown, amorphous compound of the formula Cu2OCl2. At 1250° C. in an atmosphere of nitrogen it combines with ferric oxide to the crystalline, slightly magnetic cuprous ferrite, Cu2O5Fe2O3.

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