This solution dissolves the metallic components, their oxides, and basic
zinc sulphate, and transfers cadmium and lead oxide, also lead, magnesium,
and lime sulphate, into insoluble carbonates. Iron and manganese, when
present as protoxide, are dissolved; of iron sesquioxide but traces, and
of cadmium oxide _in statu nascendi_ a small portion enter into solution.
The solution of ammonium carbonate contains in each 10 c.c. 1 grm.
ammonia, which dissolves 1.5 grm. zinc.
The sample for examination is moistened with water and mixed with an
adequate volume of the solvent, is digested at 50-60 deg. C. until complete
decomposition is effected. The heating of the liquid prevents the solution
of iron, manganese, and cadmium. The content, sediment and liquid, is
thrown on a filter and washed with hot water to which a small quantity of
the solvent has been added. When the solution contains iron and manganese,
it is separated by decantation from the sediment and oxidized with bromine
(according to the method of Nic-Wolff) until a flocculent precipitate of
iron sesquioxide and manganese dioxide becomes visible; it is united with
the original residue and filtered.
The filtrate is diluted till it appears cloudy, boiled to expel ammonia,
tested with sodium sulphide upon the presence of zinc, and, when freed of
all zinc, decanted.
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