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.