otherwise being induced to produce a zinc free of lead, the estimation of
sulphur, sulphuric acid, and lead became necessary. These impurities are
determined by well-known methods; sulphur is oxidized and precipitated
with barium chloride, lead by sulphuric acid and alcohol. The examination
of zinc dust, when used for the regeneration of metal, determines the
quantity of zinc resident therein, and employed as reducing agent, the
quantity of metal which causes the generation of hydrogen. Cadmium,
showing the same deportment, must also be considered as well as lead and
arsenic.

A most complete and rapidly working method for the examination of
zinciferous products has originated with the application of neutral
ammonium carbonate as solvent. A solution of this preparation is made,
according to H. Rose, by dissolving 230 grm. commercial ammon carbonate in
180 c.c. ammoniacal liquor of 0.92 s.g., and, by addition of water,
augmenting it to one liter.

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° 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