PIGMENTS 113
varying in color from deep blue to faint lavender. This ancient blue invariably
contains some calcite and quartz as impurities. Raehlman (pp. 67-68) has well
described, with the aid of color plates, its appearance in a paint film.
The history of Egyptian blue is largely ancient. Spurrell states (p. 227) that
it was found as early as the IV Dynasty in Egypt. Laurie ('The Identification of
Pigments . . . ,' p. 166) observed it on paintings from the palace at Knossos.
Raehlman (he. cit.), Chaptal (foe. cit.\ and others have found it on Pompeian
and other Roman wall paintings. It has further been identified as the dark blue
material of a mace bead from Nuzi, Iraq (c 1500 B.C.); as the material of the
blue inlay in ivories from Samaria; and as a blue pigment on Roman wall paint-
ings from Dura-Europos in Syria. Partington has reviewed (pp. 117-119) the
history and occurrence of Egyptian blue and he says (p. 118): *No ancient Euro-
pean people could successfully imitate Egyptian blue and the secret of its manu-
facture was lost between A.D. 200 and 700.' Lump specimens of Egyptian blue
can be seen at the Naples Museum, at the Fogg Art Museum, Cambridge, Mass.,
and at other places. A modern blue pigment called 'Pompeian blue/ which is
entirely similar in chemical composition and in optical properties to the ancient
copper-lime-silicate blue but which is purer and finer, is now available from a
French source.
Emerald Green (Schweinfurt green, Paris green) is an artificial pigment which
was first made at Schweinfurt, Germany, in 1814 (see Rose, p. 140). It is copper
aceto-arsenite (Cu^HsOg^^CufAsCya) and can be prepared in several ways,
in all of which the important raw materials are copper, acetic acid (or verdigris),
white arsenic, and sodium carbonate. These are mixed in hot solution and the
precipitate is thoroughly washed and dried (Beam, pp. 102-104 gives all the
details). Emerald green, as the pigment is now called, is bright blue-green in
color, is one of the most brilliant of the inorganic colors, and is quite unlike any
other green pigment. It has fair hiding power. Some specimens of emerald green
are quite characteristic; in these the particles consist of small, rounded grains,
uniform in size and, at high magnifications, are seen to be radial in structure.
Many particles appear to have a pit or dark spot in the center. The grains are
strongly birefracting. The particles in other samples of emerald green, however,
are not so characteristic in shape. It does not enjoy popularity as an artist's
pigment chiefly because it is blackened by sulphurous air and pigments, and also
because it is poisonous and dangerous to handle. (As Paris green, it has long
been used as an insecticide.) It is readily decomposed by acids and by warm
alkalis, and it is blackened by heat. It is fairly permanent, however, in an oil or
varnish medium.
Emerald green has not been identified frequently on paintings. De Wild found
it on only one (dating 1860). Occasionally it is seen as the green pigment used for
making an imitation patina over repairs on ancient Chinese bronzes.