Take 80 grams of litharge
and 20 grams of a mixture of borax and soda. Fuse three lots (1) with
1.5 gram of charcoal, (2) with 3 grams of flour, and (3) with 7.5 grams
of tartar. Weigh the buttons of lead obtained, and divide each by the
weight of reducing agent used. The results will differ somewhat with the
dryness and quality of the flour, etc., used; in one series of
experiments they were as follows:--
Gram. Grams. Gram. Grams.
1.5 charcoal gave 34.0 lead .'. 1 charcoal = 22.6 lead.
3.0 flour " 33.5 " .'. 1 flour = 11.2 "
7.5 tartar " 38.0 " .'. 1 tartar = 5.0 "
The use of flour as a reducing agent has many advantages, and it is well
to remember that _1 gram of flour reduces about 11 grams of lead_; and
that charcoal has twice, and tartar one-half, this reducing effect.
_On the Reducing Effect of Charcoal, &c., on Red Lead._--It is often
easier to obtain red lead of good quality than it is litharge, and by a
large number of assayers red lead is the form of oxide of lead always
used. Red lead, however, contains an excess of oxygen which will use up
some of the reducing agent before lead separates out. On making a series
of experiments (similar to the last, but using 80 grams of red lead
instead of the litharge) the results were, with the same quantities of
the reducing agents:--
With charcoal, 18 grams of lead.
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