ich it is probably an ancestral form. The European _A. magnum_ was
as large as the last-mentioned animal, but there were several smaller
species and the genus also occurs in Egypt, India and North America.
(See ARTIODACTYLA.)

ANTHRAQUINONE, C14H8O2, an important derivative of anthracene, first
prepared in 1834 by A. Laurent. It is prepared commercially from
anthracene by stirring a sludge of anthracene and water in horizontal
cylinders with a mixture of sodium bichromate and caustic soda. This
suspension is then run through a conical mill in order to remove all
grit, the cones of the mill fitting so tightly that water cannot pass
through unless the mill is running; the speed of the mill when working
is about 3000 revolutions per minute. After this treatment, the mixture
is run into lead-lined vats and treated with sulphuric acid, steam is
blown through the mixture in order to bring it to the boil, and the
anthracene is rapidly oxidized to anthraquinone. When the oxidation is
complete, the anthraquinone is separated in a filter press, washed and
heated to 120 deg. C. with commercial oil of vitriol, using about 2-1/2
parts of vitriol to 1 of anthraquinone. It is then removed to lead-lined
tanks and again washed with water and dried; the product obtained
contains about 95% of anthraquinone. It may be purified by sublimation.
Various synthetic processes have been used for the preparation of
anthraquinone. A. Behr and W.A. v. Dorp (_Ber._, 1874, 7, p. 578)
obtained orthobenzoyl benzoic acid by heating phthalic anhydride with
benzene in the presence of aluminium chloride. This compound on heating
with phosphoric anhydride loses water and yields anthraquinone,

/CO\ C6H6 /CO.C6H6 /CO\
C6H4< >O -> C6H4< -> C6H4< >C6H4.
\CO/ \COOH \CO/

It may be prepared in a similar manner by heating phthalyl chloride with
benzene in the presence of aluminium chloride. Dioxy- and
tetraoxy-anthraquinones are obtained when meta-oxy- and
dimeta-dioxy-benzoic acids are heated with concentrated sulphuric acid.

Anthraquinone crystallizes in yellow needles or prisms, which melt at
277 deg. C. It is soluble in hot benzene, sublimes easily, and is very
stable towards oxidizing agents. On the other hand, it is readily
attacked by reducing agents. With zinc dust in presence of caustic soda
it yields the secondary alcohol oxan-thranol, C6H4 : CO.CHOH : C6H4,
with tin and hydroc