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HYDROCYANIC  ACID                                                   731

Fatal Dose.—The smallest quantities that have proved fatal are half a
drachm of dilute hydrocyanic acid and 20 minims of Scheele's acid equivalent
to 0.6 grain and 1 grain of anhydrous acid respectively.   Forty-five to sixty
minims of dilute hydrocyanic  acid are likely to prove fatal to an adult.
Recovery has, however, occurred after taking 4 drachms of the dilute acid
equivalent to 4.8 grains of the anhydrous acid.   Two grains and-a-half of
pure potassium cyanide may "be regarded as a minimum fatal dose.   A dose
of 5 grains of potassium cyanide has proved fatal in some cases, though
recovery has followed much larger doses of even 50 to 60 grains.   Seventeen
as well as thirty drops of oil of bitter almonds have produced fatal results,
but recovery has taken place after doses of from 4 to 6 drachms in some
cases.    Sixty to eighty bitter almonds are sufficient to destroy the life of an
adult.   A handful of bitter almonds has caused death, while recovery has
taken place after a dose of two handfuls.    One-and-a-half to two ounces of
cherry-laurel water have caused death.

The concentration of one volume of hydrocyanic acid gas in 2,000 parts
of air is generally fatal to animals. The concentration of 0.2 to 0.3 mg. of
the gas per litre of air is regarded as sufficient to kill men almost, imme-
diately, while the concentration of 0.13 mg. per litre of air and an exposure
of over an hour are sufficient to prove fatal to men.

Fatal Period.—Two to ten minutes. It is possible that life may be pro-
longed for two to three hours, but in most cases the patient will recover, if
death does not occur within an hour.

In poisoning by potassium cyanide death usually occurs within thirty
minutes, Powell55 reports a case in which death occurred from commercial
potassium cyanide in seven to twelve minutes. A student of Lucknow Uni-
versity died within 10 to 15 minutes after taking potassium cyanide. In a
few cases death may be delayed for several hours.

Treatment.—There is hardly time for treatment, if strong hydrocyanic
acid is taken. In the case of potassium cyanide or dilute hydrocyanic acid
poisoning, wash out the stomach immediately with a dilute solution of hydro-
gen peroxide, or potassium permanganate (5 grains to the pint) or a 5 to 10
per cent solution of sodium thiosulphate. Vinegar may be added if the
poison is potassium cyanide. If a stomach tube is not available, produce
vomiting by mustard and water added by tickling the fauces or by the
hypodermic injection of apomorphine hydrochloride.

Cold affusions to the head and chest and inhalation of ammonia should
be followed by the hypodermic injection of 1/50 grain of atropine, strychnine
or caffeine and sodium benzoate, artificial respiration and oxygen inhalation.

If death is delayed, a mixture of ferrous and ferric sulphates with car-
bonate of potassium may be given as a chemical antidote to produce the
innocuous Prussian blue. Intravenous injections of glucose or glucose and
insulin are regarded as beneficial.

Administer amyl nitrite by inhalation and give intravenously 10 cc. oŁ
a 3 per cent solution of sodium nitrite immediately followed by 50 cc. of a
25 per cent solution of sodium thiosulphate and repeat them if necessary.
These are regarded as most satisfactory antidotes to hydrocyanic acid and
the cyanides.

Intravenous injection of 50 cc. of a one per cent sterile aqueous solution
of methylene blue (methyl thionine chloride, U.S.P.) has been recommended
as an antidote, Methylene blue converts the haemoglobin of the blood into

55-   r-mL Med. Gaz., Aug, 1902, p. 306.