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Was Known In Ancient Times: The Romans Called It Auri Pigmentum Or








gold colour, whence, by corruption, its present name is derived. It is
found in the native state in China and elsewhere, the best quality being
in masses, consisting of plates of a fine golden hue, intermixed with
portions of a vermilion or orange-red colour; the inferior kinds are
yellow or greenish yellow. Of orpiment, or sulphuret of arsenic, which
is produced artificially, there are two distinct varieties; one of a
bright pure yellow tint, in which the sulphur predominates, and one of
an orange hue, in which the arsenic is in excess. The former is the most
lasting, but it is not durable in water, and still less so in oil,
although not discoloured by impure air. Compounded with white lead it is
soon destroyed, nor can it be mixed with any colours into which lead
enters, such as chrome yellow, the old Naples yellow, &c. The sulphur in
combination with the arsenic, having less affinity for that metal than
for lead, lets it go, and forms a sulphuret of lead of a dark greyish
hue. Moreover, as orpiment is apt to deprive other pigments of their
oxygen, and therefore to change and be changed by all pigments whose
colour depends on that element--metallic pigments especially--it is
probable that the orpiment after some time withdraws the oxygen from the
lead; and this would be an additional cause for the darkening of the
tint composed of the two colours. With sulphides or pigments containing
sulphur, orpiment may be used with less danger. If employed at all,
however, it had better be in a pure and unmixed state. We are far from
recommending orpiment as an eligible colour, and it is highly
poisonous.

Brick dust and yellow ochre are sometimes found as adulterants.

TTITLE RAW SIENNA,





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