Modern inorganic chemistry

416 THE TRANSITION ELEMENTS

Copper(l) chloride, bromide and cyanide were used by Sandmeyer

to introduce a chlorine, a bromine atom and a cyanide group

respectively into a benzene ring by addition to the phenyl diazonium

salt.

Copper(I) sulphate, Cu 2 SO 4 , is obtained as a white powder by heating

together dimethyl sulphate and copper(I) oxide:

(CH 3 ) 2 SO 4 + Cu 2 O -> Cu 2 SO 4 + (CH 3 ) 2 O

dimethyl ether

This copper(I) compound, unlike the above, is soluble in water

and therefore in the presence of water liberates copper and forms a

copper(H) compound :

Cu 2 SO 4 -> CuSO 4 -f Cu|

COMPLEXES

The complexes of copper(I) like those of silver(I) (p. 430), but unlike

those of preceding transitions metals, tend to prefer a linear co-

ordination of two ligands, i.e. X—Cu—X; thus copper(I) chloride in

aqueous ammonia gives the colourless [Cu(NH 3 ) 2 ]+ (readily

oxidised in air to give blue [CuII(NH 3 ) 4 (H 2 O) 2 ]2+; copper(I)

chloride in hydrochloric acid gives [CuQ 2 ]~, although [CuQ 3 ]^2 ~

is also known.

TESTS FOR COPPER COMPOUNDS

Copper(II) ions in aqueous solution are readily obtained from any

copper-con taming material. The reactions with (a) alkali (p. 430),

(b) concentrated ammonia (p. 413) and (c) hydrogen sulphide (p. 413)

provide satisfactory tests for aqueous copper(II) ions. A further test

is to add a hexacyanoferrate(II) (usually as the potassium salt) when

a chocolate-brown precipitate of copper(II) hexacyanoferrate(II) is

obtained:

2Cu2+ + [Fe(CN) 6 ]^4 - -> Cu 2 [Fe(CN) 6 ]

ZINC

THE ELEMENT

The common ores of zinc are zinc blende, ZnS, and calamine, ZnCO 3.
The metal is extracted (a) by roasting blende with air or by heating