antimony - Sciencemadness.org

160 THE METALLURGY OF ANTIMONY.
M. E. Kopp * says :—" The sulphide of antimony, according to its
physical state and its mode of preparation, may present very
varied colorations. It is crystalline and black-gray in the native
state. When kept in the molten state for a long time and suddenly
cooled, it becomes hyacinth-red. Precipitated by sulphuretted
hydrogen from an antimonic solution, it is of an orange colour
more or less red. In the kermes state it is red-brown. Lastly, when
obtained from the reaction of a soluble hyposulphite upon the chloride
of antimony, its red colour is more or less bright, and more or less
orange or crimson, in accordance with the temperature employed and
the concentration of the liquors.
" This latter reaction was indicated by several chemists, who gave
recipes for the regular manufacture of the fine red sulphide of
antimony, which was called vermilion of antimony.
" All of these methods are based upon the employment of hyposulphite
of soda and chloride of antimony in quite concentrated
solutions, and they present various inconveniences.
" In the process which I have followed, the vermilion of antimony
is obtained by the reaction of the chloride of this metal upon a
dilute solution of hyposulphite of lime; and the mother-liquors are
used several times, and are thrown away only after they contain too
great a proportion of chloride of calcium.
" I am going to describe successively the various operations in the
manufacture of the red sulphide of antimony.
"1. Preparation of the Chloride of Antimony.—The decomposition
of the sulphide by HC1 is very easy in experimental laboratories, but
the operation presents great difficulties when we have to work upon
large quantities of materials.
"After a series of experiments (employment of leaden vessels,
heating stoneware vessels in sand and pitch baths, etc.), I found
that it was much better to roast the sulphide of antimony at a
moderate temperature in contact with air and steam. The greater
part of the sulphide is converted into oxide of antimony, and the
sulphurous acid produced in the manufacture of the hyposulphite of
lime. The oxide of antimony is then easily dissolved in commercial
hydrochloric acid.
"If, during the oxidation of the sulphide of antimony, there is
produced a certain proportion of antimonious acid, but slightly
soluble in HC1, it may be saved by collecting the residues from
the treatment with hydrochloric acid, and washing them with chloride
of calcium or hyposulphite of lime, which dissolves the adherent
* Bulletin de la Soci4t4 industricllc de Mulkouse, vol. xx. pp. 379 et se