Introduce these elements into a graphite or
fire-clay crucible containing forty parts of sulphur and twenty-five
parts of charcoal, raise the whole mass nearly or quite to a white heat,
remove from the fire, allow it to cool slowly, and, when it is cold or
sufficiently lowered in temperature to be conveniently handled,
remove it from the crucible and grind it. The method of reducing the
composition will depend upon the mode of its use. If it is to be applied
as a loose powder by the dusting process, it should be simply ground
dry; but if it is to be mixed with paint or other similar substance,
it should be ground with linseed or other suitable oil. In heating the
elements aforesaid, certain chemical combinations will have taken place,
and monosulphide of calcium, combined with carbonate of lime, magnesia,
and silex, will be the result of such ignition.
If, in the firing of the elements, as above set forth, all of the
charcoal does not unite with the other elements, such uncombined portion
should be removed from the fused mass before it is ground.
If it is designed to mix the composition with paints, those composed of
zinc-white and baryta should be chosen in preference to those composed
of white lead and colored by vegetable matter, as chemical action will
take place between the composition and paint last mentioned, and
its color will be destroyed or changed by the gradual action of the
sulphureted hydrogen produced.
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