A N T I M O N Y : ITS HISTORY, CHEMISTRY, MINERALOGY ...

164 THE METALLURGY OF ANTIMONY.
at the ordinary temperature or in a stove-room the temperature of
which is not over 50° to 60° C.
" While the precipitate is settling in the first tank, a similar operation
takes place in the second, and then in the third. During that
time the first tank has been emptied, and its mother-liquors have
been regenerated. These are then brought back into the first tank,
and another precipitation of vermilion of antimony takes place, and
so on.
" 4. Properties of the Vermilion of Antimony.—The vermilion of
antimony is in the state of a very fine powder, without taste or smell,
and is insoluble in water, alcohol, or essential oils. It is but little
acted upon by the weak acids, even when concentrated, or by the
powerful inorganic acids which have been diluted with water. It
stands the latter acids better than the ordinary sulphide of antimony.
Concentrated and hot hydrochloric acid dissolves it, with formation
of sulphuretted hydrogen and chloride of antimony. Nitric acid
oxidises it, with the production of sulphuric and antimonic acids. The
vermilion of antimony is not sensibly acted upon by ammonia or the
alkaline carbonates; on the other hand, the powerful caustic alkalies,
such as potash, soda, baryta, strontia, and lime, decompose it and form
combinations which are colourless, or nearly so. The colour is therefore
destroyed; consequently this pigment should not be mixed with
alkaline substances. A high temperature blackens it, and should
the heat be such as to melt it, it becomes ordinary sulphide of
antimony.
" The vermilion of antimony is an opaque pigment, without much
lustre or brightness, when mixed with water, thickened by gummy or
gelatinous substances. On the other hand, when ground in oil or
varnishes, it acquires great intensity and brightness of color, and has
good body or covering power, being superior in that respect to red
lead, orange mineral, the red subchromate of lead, and cinnabar or
mercury vermilion. A well-prepared vermilion of antimony, ground
in oil, gives possibly the purest red color; that is to say, it is not
tinged orange, or pink, or crimson; but it often has a brownish hue.
It is perfectly unalterable by air or light, and may be mixed with
white lead, which is not blackened by it, even after several years. It
does not assist or hinder the drying of oil. Therefore the vermilion
of antimony is a pigment especially fitted for oil-painting, and its low
price and covering power render it advantageous for carriage and
house painting."
(d) Antimony Yellow.—(a) Naples Yellow.—This pigment, which
is obtainable by combining lead oxide and antimonic acid together,