The chemico-technical analysis of these products has until recently been
confined to the volumetric determination of zinc by means of sodium
sulphide (Schaffner's method). But as a remnant of sulphur, as sulphuric
acid, in roasted blende causes a material loss during distillation, and
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.
Pages:
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35