HYDROCYANIC ACID. — Hydrocy anic acid, also known as cyanhydric or prussic acid, hydrogen cyanide, and f or monitrile, is official in a 2-per-cent. solu tion (acidum hydrocyanicum dilutum, U. S. P.), which is a colorless liquid, hav ing the odor and taste of bitter almonds. Dilute hydrocyanic acid is prone to de compose, becoming more or less brown in color, rendering it unfit for medicinal use; it should therefore be kept in a dark, cork-stopped bottle, and dispensed with a pipette, rather than by pouring it. The metallic salts are generally incompatible; also the red acid of mercury and the sul phides; chlorine-water and all oxidizing agents change this acid into formalic acid.
Dose.—Acidum hydrocyanicum dilu turn (2 per cent.), 1 to 15 minims.
Physiological Action.—Applied to the mucous membrane or the abraded skin, hydrocyanic acid rapidly diffuses into the blood. In medicinal doses it has a calmative effect. In larger doses it may cause nausea, faintness, giddiness, a feeble pulse, and great muscular weak ness. Owing to its great diffusibility, its absorption is very rapid. It acts prin cipally on the respiratory centre and the heart, and is eliminated very rapidly (one-half to one hour). If a larger quan tity is taken it exercises a paralyzing effect upon every part of the body; the respiration, heart, brain, nervous system, and all the vital parts are paralyzed at once.
Poisoning by Hydrocyanic Acid.— Prussic, or hydrocyanic, acid is one of the most rapid and violent poisons known. A single whiff of the pure acid will kill; it is therefore very unsafe to handle. When a large toxic dose is taken, death may occur in from two to five min utes. The usual symptoms are as follow: Sudden and complete insensibility, the eyes protrude with a glistening stare, the pupils are dilated and unaffected by light, the skin is cold and clammy, the extremities are relaxed and cold, the res piration is slow and convulsive, pulse feeble or imperceptible, and involuntary evacuations of urine, faaces, and semen. The odor on the body, the wide-staring eye, the clenched teeth covered with froth, and the livid cyanosed face are the diagnostic signs (Hare).
Series of experiments performed con sisting in ejecting amygdalin and emnl sin into the veins, so that on coming together they would form hydrocyanic acid. The changes which took place con sisted in a slowing and final arrest of the respiratory movements, followed several minutes afterward by stoppage of the heart. These same results are reached even when artificial respiration is kept up from the first. Thirty minims of a
1 to 400 solution of hydrocyanic acid injected into the jugular vein of a dog weighing 3S pounds is sufficient to pro duce death by the methods named above. When the drug is given hypodermically to the frog the same phenomena occur, preceded by a complete loss of reflex ac tivity. Gridiant (La Semaine Med., Sept. 25, '89).
Absorption of hydrocyanic acid in the eye produces death from respiratory fail ure in from two to three minutes, by the passage of the poison into the Wood. Graant (Brit. Med. Jour., Mar. 2, '91).
Results of forty-three observations upon various animals: Hydrocyanic acid stands foremost among agents likely to prove of antidotal value in chloroform poisoning. The best way to apply it is undoubtedly by means of a graduated drop-tube on the back of the tongue. The exact dose hi the dog and eat aver ages about one minim of Scheele's acid for every seven or eight pounds of live body-weight. The object must be to give just enough acid to produce the preliminary exeitant effect upon the respiratory centre. Frederick Hobday (Lancet, Jan. 1, .98).
Case of prussic-acid poisoning. The woman almost instantly fell to the floor, became unconscious, and had very severe tetanic convulsions. Her face became dusky, and she died in about twelve minutes. Autopsy one hour after death. Face slightly cyanosed; lips, mouth, and tongue slightly eroded; pupils dilated; mouth and nostrils frothy. Mu cous membrane of the stomach and upper part of the small intestines bright red in color, swollen, intensely injected. Moderate engorgement of the brain, liver, kidneys, and spleen. The lungs were much engorged and oedematous, and there were numerous subpleural ecchy moses. The blood was everywhere fluid, of a cherry-red color, and with a marked odor of prussic acid. Baker (Boston Med: and Surg. Jour., No. 19, '99).
Treatment of Poisoning by Hydro cyanic Acid.—In poisoning by hydro cyanic acid the most useful remedies are cold affusion to the head and spine; am monia by inhalation, by mouth, and by intravenous injection; artificial respira tion, atropine, and heart-stimulants. If seen early, evacuation of the stomach by emetics or irrigation may be useful, the addition of peroxide of hydrogen to the irrigating fluid being capable of trans forming any 'prussic acid present into oxamide, which is relatively harmless.
acid is used principally to allay pain and spasms when• taken internally. When applied externally it allays itching.