PIGMENTS 155
white arsenic (AssOs) in a solution of soda ash or potash and adding the hot
arsenite solution to a solution of copper sulphate. The precipitate needed only
washing and drying. De Wild says (p. 79) that the pigment consists of small and
large, irregular-shaped, green flakes which are only slightly transparent. Since
Scheele's green is inferior as a pigment, it was soon displaced by the superior
copper aceto-arsenite (see Emerald Green) when that was introduced in 1814. It
is blackened by lead and is decomposed by acids. Yellowish green when made, it
fades rapidly and is blackened by sulphur-bearing air and sulphide pigments. It
is very poisonous. Although it has not been reported in the examination of paint-
ings, one may expect to find it in works of the late XVIII and early XIX centuries.
Schweinfurt Green (see Emerald Green)*
Sepia is the black or dark brown secretion from the * ink bag ' of the common
cuttle-fish or squid (Sepia officinalis), and also from other species of the Cephalo-
poda. Although it has come from cuttle-fish of the English Channel and the
Mediterranean, most modern sepia is from Ceylon. The dark ink has very high
tinctorial power, the secretion from one cuttle-fish being able to turn a thousand
gallons of water opaque in a few seconds (see Mitchell, p. 19). For sepia prepara-
tion the ink sacs are removed from the cuttle-fish, dried, pulverized, and boiled
with lye solution. The extract, which is soluble in the lye, is precipitated out with
hydrochloric acid, is washed, and is dried at a low temperature; it is ground very
finely with gum arabic and is made into cakes or prepared in tubes for use in water
color.
Sepia is a complex nitrogenous organic compound with characteristic fishy
odor. It is in the nature of an organic acid (see Mitchell, pp. 22-25); it is soluble
in alkalis and is reprecipitated by acids. It is insoluble in water, alcohol, ether,
and similar organic solvents; it is decolorized by nitric acid and by chlorine
water. Under ordinary conditions, sepia is fairly permanent, but in strong sunlight,
especially in thin washes, it is quite fugitive. It is relatively opaque to infra-red
rays. The color of sepia, when recently applied, is warm black but it gradually be-
comes reddish brown, the color commonly associated with the name. Under the
microscope, its appearance is similar to bone black and it may be observed in
irregular, fairly coarse particles, most of which are opaque, although there are
many that are semi-transparent yellow-brown. Oil paints sold under the name,
'sepia,' are mixtures of such pigments as burnt umber, Van Dyke brown, and
lamp black.
Although there is reason to believe that sepia was known and used as early as
classical times, particularly as an ink for writing purposes (see Mitchell, p. 8), it
was not until the latter part of the XVIII century that it became popular in Eu-
rope for ink drawings and for water color painting. Meder (pp. 69-70) refers to
Hebenstreit (Encyklopadie der AesthetiK) as authority that sepia was introduced
as a color by Professor Seydelmann of Dresden some time after 1778. Until about