Copper

Copper: the essentials

 Brief description: copper is one of the most important metals. Copper is reddish with a bright metallic lustre. It is malleable, ductile, and a good conductor of heat and electricity (second only to silver in electrical conductivity). Its alloys, brass and bronze, are very important. Monel and gun metals also contain copper. Apparently the reason that policemen in the USA are nicknamed "cops" or "coppers" is to do with their uniforms which used to have copper buttons.

The most important compounds are the oxide and the sulphate, (blue vitriol).

Small and large samples of copper foil like this, as well as sheet, wire, insulated wire, mesh, and rod (and copper alloy in foil, sheet, and wire form) can be purchased from Advent Research Materials via their web catalogue.

The result of adding different metal salts to a burning reaction mixture of potassium chlorate and sucrose. The red colour originates from strontium sulphate. The orange/yellow colour originates from sodium chloride. The green colour originates from barium chlorate and the blue colour originates from copper (I) chloride. The lilac colour that should be evident from the potassium chlorate is washed out by the other colours, all of which are more intense (only to be demonstrated by a professionally qualified chemist following a legally satisfactory hazard asessment). Improperly done, this reaction is dangerous!

Copper (I) chloride salts imparts a blue colour to flames. The picture above shows the colour arising from adding cuprous chloride (CuCl) to a burning mixture of potassium chlorate and sucrose. This flame is relatively cool. Hotter flames burn green bacause of emission from copper atoms (only to be demonstrated by a professionally qualified chemist following a legally satisfactory hazard asessment).

Isolation

Isolation: copper metal is readily available commercially so it is not normally necesary to make it in the laboratory. Most copper production is based upon sulphide ores containing little copper but quite a lot of iron. New cleaner technologies are now important but older processes present major environmental problems. Complex procedures are used initially to form a form of copper sulphide appropriate for final reduction via a copper(I) oxide. The resulting crude copper is purified using an electrolytic procedure involving plating onto pure copper cathodes.

2Cu₂S + 3O₂ → 2Cu₂O + 2SO₂

2Cu₂O + Cu₂S → 6Cu + SO₂

Notably, the purification step leaves an "anode slime" which contains useful amounts of silver and gold.

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