ACIDUM HYDROCYANICUM DILUTUM, B.P.
DILUTED HYDROCYANIC ACID.
HCN = 27.018.
Hydrocyanic acid, HCN, or prussic acid, is prepared by distilling potassium ferrocyanide with diluted sulphuric acid. The Brussels Conference agreed that diluted hydrocyanic acid should contain 2 per cent., by weight, of real acid; the B.P. and U.S.P. solutions are of this strength. The U.S.P. diluted acid is prepared extemporaneously by mixing diluted hydrochloric acid, U.S.P., 15.54, with distilled water, 44.1, adding silver cyanide, 6, shaking the whole together in a glass-stoppered bottle, and pouring off the clear liquid when the precipitate has subsided. Diluted hydrocyanic acid occurs as a colourless liquid, with a characteristic odour. Specific gravity, 0.997. It should be kept in a cool, dark place, in small amber-coloured bottles, inverted, with well-fitting stoppers tied over with impervious tissue.
Action and Uses.—Diluted hydrocyanic acid is a powerful poison, and acts alike on all forms of living tissue. It is absorbed with great rapidity, and in lethal doses paralyses respiration and the heart. One of the first effects of the acid is to excite the medulla powerfully, especially the respiratory centre, and veterinary surgeons frequently employ it as a stimulant to animals in danger of death during anaesthesia. It is used in therapeutics on account of its depressing effect on sensory nerve-endings. Thus, dilute solutions (about 1 in 20) may be applied to the skin to relieve irritation and itching in such conditions as lichen and urticaria. Taken internally its action exerted on the stomach is especially useful in gastrodynia, the vomiting of pregnancy, and other forms of vomiting. Of more doubtful value is its employment internally in the treatment of cough; used as an inhalation, 1/2 to 1 mil (8 to 15 minims) of the acid in six times its volume of cold water, it may allay dry useless cough, such as the dry hacking cough of phthisis and whooping cough. Aqua Laurocerasi and Aqua Amygdalae Amarae contain 0.1 per cent. of real hydrocyanic acid. It is incompatible with salts of copper, iron, silver, and mercury. In cases of poisoning by hydrocyanic acid, death generally occurs in a minute or two; but, when this is not the case, artificial respiration should be resorted to, and the following mixture given as an antidote:—6 decigrams (10 grains) of ferrous sulphate; 4 mils (60 minims) of tincture of ferric chloride, and 30 mils (1 fluid ounce) of water, followed by 12 decigrams (20 grains) of potassium carbonate, dissolved in 30 mils (1 fluid ounce) of water. Ammonia (inhaled and internally) and brandy should also be given as stimulants.
Dose.—1 to 4 decimils (0.1 to 0.4 milliliters) (2 to 6 minims), freely diluted.
- Mistura Acidi Hydrocyanici Composita, B.P.C.—COMPOUND HYDROCYANIC ACID MIXTURE. Syn.—Brompton Hospital Mixture.
- This preparation is a sedative cough mixture, employed especially in phthisis. It contains 2 1/2 minims of diluted hydrocyanic acid and 7 1/2 minims of solution of morphine hydrochloride in 4 fluid drachms. Dose.—8 to 15 mils (2 to 4 fluid drachms).
- Vapor Acidi Hydrocyanici, B.P., 1885.—INHALATION OF HYDROCYANIC ACID.
- Diluted hydrocyanic acid, 10 to 15 minims; cold water, 1 fluid drachm. This preparation is used to lessen irritability of the respiratory passages, and to allay cough.
ACIDUM HYDROCYANICUM FORTIUS.
STRONGER HYDROCYANIC ACID.
HCN = 27.018.
Synonym.—Scheele's Hydrocyanic or Prussic Acid.
Stronger hydrocyanic acid is an aqueous solution of hydrogen cyanide, HCN, prepared by distilling potassium ferrocyanide with diluted sulphuric acid. The product should contain 4 per cent. of real acid. It occurs as a colourless liquid, with a characteristic unpleasant odour. Specific gravity, 0.994. It should not contain more than traces of sulphates or chlorides, and should leave no residue when evaporated to dryness. It should be kept in a cool, dark place, in small amber-coloured bottles, inverted, with well-fitting stoppers tied over with impervious tissue.
Use.—Stronger hydrocyanic acid is employed chiefly for poisoning animals. It is seldom used in medicine.
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.