Hydrocyanic acid

“ Group XXIII. Cyanogen.—This includes compounds of cyanogen such as hydrocyanic (prussic) acid, cyanides of potassium, sodium, &c., cherry-laurel water, amygdalin, bitter almonds and other chemical and vegetable substances which readily yield hydrocyanic acid. Hydrocyanic acid is a general protoplasmic poison, all the lower organisms being very susceptible to its action, while in the higher animals it speedily depresses or paralyses all forms of nerve tissue. It enters into combination with haemoglobin, forming a bright scarlet compound and interfering with respiration. ”

“ In order to obtain the latter in an anhydrous form, the decomposition of heated mercury cyanide by hydrogen sulphide may be made use of. Here the sulphur and cyanogen change places, and hydrocyanic acid and mercury sulphide are formed: Hg (CN) 2 + H2S = 2HCN + HgS.
[45] A weak (up to 2 p.c.) aqueous solution of hydrocyanic acid is obtained by the distillation of certain vegetable substances. The so-called laurel water in particular enjoys considerable notoriety from its containing hydrocyanic acid. It is obtained by the steeping and distillation of laurel leaves. ”

“ It has a peculiar odor, suggesting bitter almonds, and is extremely poisonous either when inhaled or when taken into the stomach. A single drop may cause death. It dissolves readily in water, its solution being commonly called prussic acid.
The salts of hydrocyanic acid are called cyanides, the cyanides of sodium and potassium being the best known. These are white solids and are extremely poisonous.
Solutions of potassium cyanide are alkaline. A solution of potassium cyanide turns red litmus blue, and must therefore contain hydroxyl ions. ”

“ Now, the very slight ionization of mercuric cyanide enables us to realize, in the following experiment, the case where an exceedingly weak acid without the formation of any precipitate involving physical constants, may displace a much stronger acid from its salts. Hydrocyanic acid is one of the weakest acids (table, p. 104) , the constant for the ratio [H+] × [CN−] / [HNC] being 0.7E−9. It is so weak an acid that the addition of a dilute solution to methyl orange will not redden the indicator, but will have only a barely perceptible effect on it (exp.) ”

“ Sometimes it is necessary to determine the strength of diluted hydrocyanic acid; because, on account of its tendency to decomposition, doubts may be entertained whether a mixture which contains it is strong enough to be dangerously poisonous. According to Orfila, the best method of ascertaining the strength either of a pure solution or of a mixture in syrup, is to throw down the acid with the nitrate of silver and dry the precipitate ”

“ Following up analogies here, I would class cyanogen and sulphur together, and so I would their hydrides. HS, like cyanogen, is not strongly acid, indeed probably not acid at all, for as in the case of hydrocyanic acid HS exhibits a great tendency to oxidize when in contact with water and to form oxyacids, so that in testing this gas for acidity we are liable to obtain reactions not due to the gas itself. ”

“ OF POISONING WITH HYDROCYANIC ACID. The poisons, whose energy depends on the presence of the prussic or hydrocyanic acid, are of great interest to the physiologist as well as the medical jurist. Some of them are natural productions, derived from the leaves, bark, fruit-kernels, and roots of certain plants; others are formed artificially by complex chemical processes. The species to be here noticed are the hydrocyanic acid itself, and the essential oils and distilled waters of the bitter almond, cherry-laurel, peach-blossom, cluster-cherry, mountain-ash, and bitter cassava. ”

“ Many nitrogenous substances,853 when submitted to destructive distillation, also evolve hydrocyanic acid. Crystallised ammonic formiate subjected to heat in a retort yields a vapour which, passed through a red-hot tube, decomposes into this acid and water. Another method by which it may be obtained, consists in sending a current of dry sulphuretted hydrogen gas through a long tube filled with cyanide of mercury ”

“ In the British Pharmacopœia there is an Aqua Laurocerasi—laurel water—prepared from the leaves. It contains 0.1 per cent. of hydrocyanic acid. It should be used with extreme caution, as the amount of hydrocyanic acid contained in the leaves is uncertain. Death has frequently resulted from its use. The most important case, however, is that of Sir T. Broughton. His mother, who gave him his usual draught on the morning of his death, observed that it had a strong smell of bitter almonds. Two minutes after he took it she observed a rattling or gurgling in his stomach ”

“ The period within which hydrocyanic acid usually proves fatal is fixed with considerable accuracy, not only by the cases observed in the human subject, but likewise by the experiments of many physiologists, and more especially those of Schubarth (p. 583) . It is probable that very large doses occasion death in a few seconds; and at all events a few minutes will suffice to extinguish life when the dose is considerable; but if the individual survive forty minutes, he will generally recover. ”

“ The effects of hydrocyanic acid on the animal system have been examined by several physiologists. The best experiments with the concentrated acid are those of M. Magendie; who says that, if a single drop be put into the throat of a dog, the animal makes two or three deep hurried respirations, and instantly drops down dead; that it causes death almost as instantaneously when dropped under the eyelid; and that when it is injected into the jugular vein, the animal drops down dead at the very instant, as if struck with a cannon ball or with lightning. ”

“ One of the salts of hydrocyanic acid, the cyanide of potassium, claims a short notice, since it is largely employed by photographers, workers in electrotype, &c. It has been taken as a poison. This salt is sold in the form of deliquescent white crystals, or in crystalline masses, which are very soluble in water, and possess the odor of prussic acid. From three to five grains will destroy life almost as rapidly as prussic acid itself, and in the same manner: a dose of five grains has proved fatal. ”

“ When the potash is saturated, the operation is completed. The Germans recommend a strong, alcoholic solution of potassa to be used in the second vessel, for in this case, the hydrocyanic or prussic acid combines with the potassa, forming a hydrocyanate of potassa, or, the water being abstracted, the cyanuret of potassium, which spontaneously precipitates, on the saturation of the fluid, the cyanuret, being insoluble in strong alcohol. The ferrocyanate of potash may be considered as containing three equivalents of hydrocyanic acid, two of potash and one of iron ”

“ The symbols [H+] , [CN−] and [HCN] denote the final concentrations for the condition of equilibrium, indicated in the equations on p. 180; in such a mixture [H+] is not equal to [CN−] , as it is in pure solutions of hydrocyanic acid in water. [CN−] , representing the total concentration of the cyanide-ion, is very much larger than [H+] , since the salt, potassium cyanide, produces the cyanide-ion in large concentrations. ”

“ In fact the imbibing of acid or bitter substances subjects us to sensations more or less painful, according to their degree. It is said that the cause of the rapid effects of hydrocyanic acid is that the pain is so great as to be unbearable by the powers of vitality. ”

“ Hydrocyanic or prussic acid, which consists of 1 atom of cyanogen = 26, + 1 of hydrogen = 1, is prepared by distilling the mercurial bi-cyanide in a glass retort with the saturating quantity of dilute muriatic acid. Prussic acid may also be obtained by precipitating the mercury by sulphuretted hydrogen gas from the solution of its cyanide; as also by distilling the ferrocyanide of potassium along with dilute sulphuric acid. Prussic acid is a very volatile light fluid, eminently poisonous, and is spontaneously decomposed by keeping, especially when somewhat concentrated. ”

“ Cyanic and cyanous acids are not poisonous, according to the experiments of Hünefield; [1893] but cyanogen is a powerful poison, as will be mentioned under the head of the Narcotic Gases.
The symptoms of hydrocyanic acid observed in man are very similar to those witnessed in animals. ”

“ Even that deadliest of poisons, hydrocyanic acid, is probably assimilated, and helps to make living tissue, if it do not kill the patient, for the assimilable elements which it contains, given in the separate forms of amygdalin and emulsin, produce no disturbance, unless, as in Bernard's experiments, they are suffered to meet in the digestive organs. A medicine consisting of assimilable substances being then simply unwholesome food, we understand what is meant by those cumulative effects of such remedies often observed, as in the case of digitalis and strychnia. ”

“ Hydrocyanic acid, again, which is so deadly a poison to animals, caused rapid movement of the tentacles. But as several innocuous acids, though much diluted, such as benzoic, acetic, &c., as well as some essential oils, are extremely poisonous to Drosera, and quickly cause strong inflection, it seems probable that strychnine, nicotine, digitaline, and hydrocyanic acid, excite inflection by acting on elements in no way analogous to the nerve-cells of animals. ”

“ Hydrocyanic acid is not considered a cumulative poison,—that is, the continued use of frequent small doses is not believed to possess the power recognised in iodine, mercury, and foxglove, of gradually and silently accumulating in the body, and then suddenly breaking out with dangerous or fatal violence. ”

“ The appearance is indeed very general in cases of poisoning with preparations containing hydrocyanic acid. Besides occurring in the case of Hufeland, and in that which gave occasion to Dr. Paris’s statement, it was witnessed by Mertzdorff, and in the instance described in Horn’s Journal. But it is not a constant appearance; for it was not observed in the seven Parisian epileptics. Neither is it peculiar; for death from carbonic acid has the same effect; I have remarked it six hours after death in a woman who died of cholera ”

“ Hydrocyanic acid gas should not be used in closely built apartments with single walls between, as more or less of the gas will penetrate a brick wall. An inexperienced person should never use cyanide of potassium for any purpose, and if it be found practicable to treat buildings in general for the extermination of insects, the work should be done only under the direction of competent officials. ”

“ With hydrocyanic acid aldehydes form the cyanhydrins R·CH (OH) ·CN. They react with hydroxylamine and phenylhydrazine, with the formation of aldoximes and hydrazones. (For the isomerism of the aldoximes see Oximes) . ”

“ But more generally a larger dose, or about seven drops, has been found necessary to kill a middle-sized dog. Five drops, according to Göppert, will kill a rabbit in six minutes. When entirely freed of hydrocyanic acid, it becomes, as already mentioned, not more poisonous than common volatile oils.
Symptoms in Man.—The effects of the almond and of the oil upon man are equally striking with those of hydrocyanic acid.
In small doses the bitter almond produces disorder of the digestive organs, nausea, vomiting, and sometimes diarrhœa. ”

“ Cyanogen, it may be mentioned, plays an important part in many organic reactions and compounds.
Gay-Lussac observed that the action of chlorine on hydrocyanic acid replaced the hydrogen forming cyanogen chloride, or acide chlorcyanique of his day; and he found that when beeswax was bleached by means of chlorine, it lost hydrogen and took up an equal volume of chlorine. At a royal ball at the Tuileries, in the reign of Charles X. (brother of Louis XVI.) , the guests were "much annoyed by the irritating vapours which came from the wax candles to illuminate the apartments." ”

“ If any medicines could produce a distant effect by a mere contact with the coats of the stomach, such a power would be ascribed to those stimulants and sedatives which, from the suddenness of their action, are called diffusible. Such are Hydrocyanic Acid and Ammonia. Their rapidity of action is to be ascribed to their volatility, whereby they spread over a large surface, and are almost suddenly absorbed and transmitted through the blood. But Hydrocyanic Acid may be absorbed from any surface. It is poisonous when inhaled into the lungs. ”

“ It carries the hemoglobin to the blood in its most easily assimilable form and its hydrocyanic acid possesses remarkable sedative powers....”
It is not possible for it to have any value in anemia because of its insolubility, yet we are told:
“In conditions marked by poverty of the blood producing anemia or chlorosis, reacting on the nervous system and calling for a chalybeate, hydrocyanate of iron (Tilden’s) takes a front rank among the remedies of this class, combining as it does the blood enriching qualities of ferrum with the sedative action of hydrocyanic acid.” ”

“ Hydrocyanic-acid gas is dangerous to human beings, but is noninflammable and nonexplosive as used in household fumigation as here advocated. It is lighter than air, will injure no fabric or painting, and will not tarnish household metals. ”

“ For instance, a mixture of citric acid with a much smaller amount of potassium nitrite and a trace of bicarbonate of iron, if exposed to light, will generate hydrocyanic acid. That, I believe, is what actually happens in some plant tissues. Animals rarely touch such plants. I believe that such a process might be aided rather than retarded by ultra-violet rays. What do you think of it?"
Craig was following Dr. Haynes keenly. As for me, I was astounded by his frankness. I recalled what Kennedy had already said up in Delaney's apartment, and watched his face covertly. ”