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ARSENIC                                                          497

Arsenious oxide is a pliarmacopceial preparation, and is called arseni-
trioxidum, the dose being 1/60 to 1/12 grain. Liquor arsenicalis (Fowler's
solution) is an official preparation, derived from arsenious oxide. Its dose
is 2 to 8 minings.

Arsenites.—These are formed when arsenious acid combines with alkalies
and their carbonates or with other metals. The alkaline arsenites thus
formed are soluble salts. The arsenites that are commonly used as poisons

1.    Potassium Arsenite, K3AsO3 and Sodium Arsenite, Na3AsO3.—These
are both poisonous, and are used in manufacturing fly papers, sheep-dips and

2.    Copper Arsenite (Scheele's Green), CuHAsOs and Copper Aceto-
arsenite   (Paris   Green,   Schweinfurt   Green   or  Emerald   Green),   Hirwa,
Cu (C2H3O;>)2, 3Cu (AsO2)2»—These are insoluble in water, but soluble in
acid juices of the stomach.   They were extensively used for colouring arti-
ficial flowers, wall papers, articles of dress, toys and sweetmeats, but they
have now been replaced by aniline dyes.    They are used as insecticides for
spraying fruit trees.

Arsenic Acid, HsAsO^.—This is obtained by warming arsenious oxide
with nitric acid, when oxides of nitrogen are given off. Arsenic acid is a
white, crystalline solid, and is used in manufacturing aniline dyes and fly
papers. It is less poisonous than arsenious acid. When deprived of water
by heating, arsenic acid changes into a white, amorphous powder, known as
arsenic anhydride or arsenic pentoxide, As^Os.

Arsenates.—Arsenic acid combines with metals to form salts, called arse-
nates. The arsenates of the alkali-metals are soluble in water, while those
of the other metals are insoluble in water. The chief alkaline arsenates are
sodium arsenate, Na3AsO4 and potassium arsenate, K3AsO4. Both these
salts are poisonous and are used for homicidal purposes and for destroying

Anhydrous sodium arsenate (Sodii arsenas anhydrosus) is a white
powder, soluble in water. It is a non-official preparation, the dose being 1/40
to 1/10 grain.

Arsenic Sulphides.—These are found naturally as ores of arsenic, the
chief being realgar, red arsenic or arsenic disulphide, As>S2 and orpiment,
yellow arsenic or arsenic trisulphide, AsoSa. They are known in the verna-
cular as manseel and hartal respectively. Both these varieties are used as
pigments in the arts. Mixed with two parts of slaked lime, orpiment is
commonly used as a depilatory to remove superfluous hair, and may be used
in tanning to remove hair from hides, but realgar is largely used for the latter
purpose. Orpiment is also used as a pigment in King's Yellow.

Both the sulphides in the pure form, being insoluble, are said to be non-
poisonous but, in the commercial form, are invariably found to contain a
large proportion of arsenious oxide, which renders them poisonous.

Arsenic Trichloride, AsCI3.—This is formed by burning arsenic in chlo-
rine or by the action of hydrochloric acid on arsenious acid. It is a highly
poisonous, colourless, fuming liquid, and is used in the treatment of
cancerous tumours.

Arsenic Triiodide (Arsenious Iodide), Asl3.—This is obtained by heating
a mixture of iodine and arsenic. It occurs in small, orange-coloured crystals
or crystalline masses, and is soluble in water, in alcohol, in chloroform, in
ether and in carbon bisulphide. It is contained to the extent of 1 per cent
in the non-official preparation, Liquor Arseni et Hydrargyri lodidi (Donovan's
solution) j the dose being 5 to 15 minims.