" flour, 18 " "
" tartar, 22 " "
Comparing these with the results with litharge, in the previous table it
will be seen that the same quantity of reducing agent has in each case
brought down 16 grams less of lead, so that a larger amount of the
reducing agent must be added to get a button of the same weight as that
obtained with litharge. To get a button of a desired weight, say 22
grams, we must add reducing agent sufficient to throw down 22 + 16 or 38
grams of lead, which would require 3.4 grams of flour. If this amount of
flour is fused with 80 grams of red lead, a button of lead weighing 22
grams will be formed, the other 16 grams being kept up by the oxygen of
the red lead.
If the quantity of red lead differs from 80 grams, this rule must be
modified. With 40 grams of red lead, for example, we should add an
excess of reducing agent sufficient to throw down 8 grams of lead
instead of 16. Similarly, with 160 grams of red lead, we should add
enough to throw down 32 grams.
The following rule will enable one to calculate the weight of flour
required to produce a button of lead of any desired weight from any
given quantity of red lead. Each 5 grams of red lead present diminishes
the weight of the lead by 1 gram. If then we _divide the weight of red
lead in a charge by 5, and add this to the weight of lead required, the
sum divided by 11 will give the weight of flour which must be added_.
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