Copper-Plating on Zinc.
Take an organic salt of copper—for instance, a tartrate. Dissolve 126 grammes sulphate of copper (blue vitriol) in two litres of water; also 227 grammes tartrate of potash and 286 grammes crystallized carbonate of soda in 2 litres of water. On mixing the two solutions, a light bluish-green precipitate of tartrate of copper is formed. It is thrown on a linen filter and afterwards dissolved in half a litre of caustic soda solution of 16° B. when it is ready for use.
The coating obtained from this solution is very pliable, smooth and coherent, with a fine surface; acquires any desired thickness if left long enough in the bath.
Other metals can also be employed for plating, in the form of tartrates. Instead of tartrates, phosphates, oxalates, citrates, acetates and borates of metals can be used; so that it seems possible to entirely dispense with the use of cyanide baths.