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.



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Violet De Mars Purple Ochre Or Mineral Purple Is A Dark Ochre We Have Adopted The Term Marrone Or Maroon As It Is Sometimes Called facebooktwittergoogle_plusredditpinterestlinkedinmail

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