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HYDROCYANIC ACID                                                      733

injected vessels. The stomach was empty. Its mucous membrane was red,
inflamed and presented a velvety appearance. The stomach wall was thick-
ened, corrugated and the vessels were injected, The small intestine con-
tained reddish liquid matter. The mucous membrane in its upper part was
red and inflamed with haemorrhagic patches under it, and the vessels were
injected. The lower parts of the small intestine and the large intestine
were normal. The large intestine contained liquid faecal matter. The liver
was dark red and congested and the spleen and kidneys were congested.
The bladder was empty. Potassium cyanide was detected in the viscera
usually preserved for chemical analysis.

Chemical Analysis.—It is very necessary that the chemical analysis of
the viscera should be made as soon as practicable after death, as hydro-
cyanic acid, being a volatile and unstable compound, is readily decomposed,
especially if the conditions favouring putrefaction are present. However,
the acid has been detected in putrefied viscera a long time after death.
Thus, Autenrieth50 detected its presence after 60 days when the organs were
in a high state of decomposition. Jollyman 5T found potassium cyanide in the
stomach contents of a Negro six months after death.

From organic mixtures acidified with tartaric acid, hydrocyanic acid
may be separated by distillation with steam.

Tests.—1. If a strip of white paper is moistened with copper-benzidine
solution and dipped into the suspected organic mixture, the paper assumes
a distinct blue colour if hydrocyanic acid is present. Copper-benzidine solu-
tion is prepared by adding 1 cc. of a 3 per cent solution of copper acetate
and 5 cc. of a saturated solution of benzidine in glacial acetic acid to 15 cc.
of water.

2.    Silver Nitrate, Test.—A drop of silver nitrate solution is placed on
a microscopic slide which is inverted over a wide-mouthed flask containing
the suspected material.   On gently heating the flask on a water bath, the
silver nitrate solution assumes a white turbidity from the formation of silver
cyanide.   When examined under the microscope, the turbidity is seen to
consist of needle-shaped crystals.

3.    Prussian Blue Test.—A portion of the distillate is made slightly
alkaline with a 5 per cent solution of sodium hydroxide and treated with a
few drops of a freshly prepared 5 per cent solution of ferrous sulphate and
1 or 2 drops of a 3 per cent solution of ferric chloride.   The mixture is
shaken well, allowed to stand for 2 minutes, warmed gently and acidified
with dilute hydrochloric acid.   A precipitate of Prussian blue is formed if
much hydrocyanic acid is present in the distillate, while a greenish-blue
colour develops if hydrocyanic acid is present in traces only.

4.    Sulphocyanide (TTiiocyanate) Test.—A few cubic centimetres of the
distillate are treated with a few drops of potassium hydroxide solution and a
little yellow ammonium sulphide and evaporated to dryness on a water bath.
The dry residue is dissolved in a small amount of water and acidified with a
few drops of dilute hydrochloric acid.   The solution is filtered and to the
filtrate are added 5 to 10 drops of neutral ferric chloride solution.   A blood-
red colour will develop, if hydrocyanic acid or a cyanide is present.   The
colour will disappear on the addition of mercuric chloride solution.

Medico-Legal Points.—Hydrocyanic acid and various cyanides are often
used for suicidal purposes, as their swift and sure action is generally known.

A Bengali student who failed at the University examination swallowed the contents
of a bottle of hydrocyanic acid.   There was time to remove him to the Medical College

56,    Detection of Poisons, Ed. VI, p. 36 (Eng. Trans, by Warren).

57.    Ibid., p. 37; Chemilker-Zeitung Jahragg., 1905, 29, p. 350.