CHAPTER VIIHEAVY METALS OF GROUPS I AND II OF
THE PERIODIC SYSTEM
The metals coming under this heading constitute the right-
hand or B Families in Groups I and II of the periodic system.
They possess high specific gravities, and chemically they are far
less active than the metals of the corresponding A Families,
reacting but little or not at all with water or air. They are base-
forming with the exception of gold, and their oxides yield fairly
stable salts with the strong acids; their basic properties, however,
are comparatively weak, and the oxides of some of them show very
feeble acidic properties as well.
Copper, silver, and gold in Group I show a similarity to sodium
and potassium principally in the fact that they form certain
compounds of the same type, for example, M 2 O and MCI. Zinc,
cadmium, and mercury in Group II resemble calcium, barium, and
strontium in that they form compounds of the types MO, MSO4,
MCI2, etc. In other respects, the divergence in the properties of
the elements of the A and B Families is at a maximum in these
two groups.PREPARATION 27
CRYSTALLIZED COPPER SULPHATE, CUSO4-5H 2 O
(BLUE VITRIOL)
On account of the fact that copper has not the power of displac-
ing hydrogen from acids, it is not possible to dissolve it directly in
dilute sulphuric acid. But although the metal itself is so difficult
to attack with non-oxidizing acids, nevertheless copper oxide is
readily dissolved by all acids; and thus the problem is to convert
copper into its oxide. The cheapest source of oxygen is the atmos-
phere, and on the commercial scale, the usual method of obtaining
copper sulphate from scrap copper is to allow dilute sulphuric acid
to drip slowly over the latter, to which air is given free access.
Since, however, this method would be too time-consuming for the
220