PIGMENTS
became fixed to the artificial pigment, red lead. Pliny says that almost the entire
Roman supply came from Sisapo in Spain. This source was probably the famous
Almaden mines which today are still the world's most important source of mer-
cury. He speaks of its use as a pigment and says that it was costly and its price
was fixed by the government. The pigment, vermilion, has been identified numer-
ous times on Pompeian and Roman wall paintings. Lucas makes no mention of it
as a pigment in ancient Egypt, and there is some question as to whether or not it
was used in Mesopotamia and the Near East. The pigment has been known in
China since prehistoric times and it has long been held in high esteem there. It
was identified as the red in the fossae of the incisions of the famous Chinese oracle
bones (see A. A. Benedetti-Pichler, ' Microchemical Analysis of Pigments,'
Industrial and Engineering Chemistry, Analytical Edition^ IX [1937], pp. I49~~
152) which date from the Shang epoch in the second millenium B.C. It was used
by the Chinese, probably as early as Han times, for making the red ink which is
so often seen on cartouches and stamp seals of early Chinese silk and scroll
paintings.
Cinnabar is fairly widely distributed in nature and sources are known in Eng-
land, Europe, China, Japan, California, Mexico, Peru, as well as in Spain. Soon
after classical times, artificial cinnabar is noticed. Geber (or Jabir), the VIII—
IX century Arabic alchemist, speaks about a red compound formed by the union
of sulphur and mercury (see Kopp, IV, 184—188). Recipes for its preparation are
common in the Middle Ages. From writings of Cennino Cennini, the vermilion
of the Italian painters of the XV century is supposed to have been artificial. He
says (see Thompson, The Craftsman** Handbook^ p. 24): *A color known as
vermilion is red and this color is made by alchemy prepared in a retort.* Even in
China they knew very early how to make vermilion by the dry method. They
may have been the first to make it artificially, and their knowledge of the process
could have been carried to the West by the Moors.
The dry method of preparation was the one used by the ancient alchemists
and is used, probably, by the Chinese at the present time. In the Dutch modifica-
tion of the Chinese method, loo parts (by weight) of mercury are combined in an
iron pan with 20 parts of molten sulphur to form black amorphous mercuric sul-
phide (ethiops mineral). The black mass is charged into retorts where it is heated,
and by sublimation and condensation on earthenware pots or iron cylinders is
changed into the red crystalline modification of mercuric sulphide. The product
has only to be treated with a strong alkali solution to remove free sulphur, and to
be washed and ground under water to prepare it as a pigment. The change from
black mercuric sulphide to vermilion is entirely physical. This dry-process ver-
milion, particularly that produced by the Chinese (Chinese vermilion), is rather
coarsely crystalline and slightly violet-red in color.
The wet method has found favor with English, German, and American pro-
ducers. It was known as early as the XVII century that the red modification of