Treatise on Poisons by Sir Robert Christison

hydrochloric acid in _compound organic mixtures_ a process, to which Professor Orfila has since made an important addition,[312] and which the investigations of that toxicologist, as well as my own, lead me to suppose superior to any other yet suggested, although it is not entirely free from objection. This process divides itself into two, according as the subject of analysis is acid or neutral; but in the latter case its indications are of dubious import. a. If the matter to be examined be acid, boil it with water if necessary, filter, and distil it with a gentle heat till the residue acquire the consistence of a very thin syrup. Subject the distilled liquor to the tests for diluted hydrochloric acid. It will seldom be found there, however, because it is apt to be retained by the co-existence of organic matter. If it be not found, add to the thin extract in the retort a slight excess of a strong solution of tannin, filter, and distil the filtered liquid by means of a hot bath of solution of hydrochlorate of lime (consisting of two parts of crystallized salt and one of water,)—taking care that the temperature of the bath never exceeds 240°; and stop the distillation just before the residuum becomes dry. Examine now the distilled liquor with the tests for diluted hydrochloric acid. Hydrochloric acid has a tendency to adhere with obstinacy to organic matters, especially when these are abundant; and therefore Orfila properly proposes to remove organic principles as far as possible by precipitating them with solution of tannin. I have found, as he did, that the acid may be obtained by distillation after this measure, when it could not be obtained previously.—Orfila objects to the process however that hydrochlorate of ammonia will pass over in the distillation. But I have not found this to be the fact, when the temperature did not rise above 240°; which in his experiments seem to have been considerably exceeded.—A more important fallacy is, that hydrochloric acid will be indicated by the process in a mixture which contains both a neutral chloride, such as common salt, and sulphuric acid. This fallacy can only be obviated by ascertaining that sulphuric acid is not present.—But the most important fallacy of all is, that free hydrochloric acid constitutes an essential part of the gastric juice, and an ingredient of the secretions of the stomach in various states of disordered digestion.[313] It is not easy to see how this fallacy can be obviated, unless the acid be obtained in large quantity; nor am I prepared to say what quantity would justify the conclusion, that the acid had been derived from an external source. Dr. Prout once found between four and five grains of pure acid in sixteen ounces of the fluid of water-brash.[314] The quantity of hydrochloric acid is to be known by drying, heating and weighing the chloride of silver thrown down in the distilled fluid by nitrate of silver, and allowing 100 parts of concentrated commercial acid for 145 of chloride. b. When the mixture is neutral, hydrochloric acid can be no longer detected in it without the aid of sulphuric acid to decompose the chloride that has been formed. This should be added to the filtered fluid obtained after organic matter has been separated by solution of tannin. Hydrochloric acid will then distil over.—It is seldom however that the discovery of the acid in this way will warrant the conclusion, that it had ever existed free in the mixture whence it is obtained. For it may have proceeded from chlorides contained in the subject of analysis from the first, more especially chloride of sodium, which exists in small quantity in all animal fluids and solids, and more largely in many articles of food and drink. The only circumstance indeed in which the detection of hydrochloric acid by decomposition with sulphuric acid will yield any evidence,—and even then the evidence will only be presumptive,—is when it is known that an earth or alkali was given as an antidote, and when the alkali or earth which was used is found in the suspected substance. SECTION II.—_Of the Action and Symptoms produced by Hydrochloric Acid._ Hydrochloric acid has been found by Professor Orfila to exert the same action as sulphuric and nitric acids; but it is a less powerful corrosive and irritant.—In the gaseous state, it is a most destructive poison to vegetables, as will be shown in the article on the Poisonous Gases. The symptoms it occasions in man are very like those produced by sulphuric acid. As few cases however of poisoning with this substance have yet been published, its effects are not so well known as those of the other powerful acids; and it may therefore be right to mention the leading particulars of some of the cases which are met with in authors.—Mr. Quekett has related the case of a man, who, on arriving at home one day, told the woman he lodged with that he had poisoned himself with spirit of salt, but presented at the moment so little sign of uneasiness, that she at first scarcely believed him. In a short time however he suddenly became faint and fell down. On being removed to the London Hospital, magnesia and milk were given, about three hours after the acid had been taken; but no relief was experienced. He suffered intense thirst, complained of excessive pain in the stomach and throat, and expired in about fifteen hours.[315]—Mr. J. F. Crawfurd of Newcastle has related a still more rapid case which was occasioned by two ounces of an equal mixture of hydrochloric acid and “tincture of steel,” probably the tincture of chloride of iron. Vomiting occurred soon afterwards, but subsequently ceased; there was no complaint made either of pain or heat anywhere, or of thirst; and questions were answered intelligently. But the pulse was imperceptible, and the muscles of the extremities contracted; and death took place in five hours and a half.[316]—Orfila mentions that an hospital patient, affected with inflammation of the brain after a fall on the head, having got by mistake from his nurse 45 grammes, or two fluid ounces, of hydrochloric acid, was attacked with acute pain in the stomach, efforts to vomit, hiccup, extreme restlessness, a small pulse, a fiery red tongue, blackness of the lips, and a burning skin; and next day he died in a state of constant delirium, and covered with a cold clammy sweat.[317] These cases present nearly the same violence and variety of action with that which results from the two other acids. SECTION III.—_Of the Morbid Appearances caused by Hydrochloric Acid._ The morbid appearances are on the whole similar to what are caused by sulphuric acid. In Mr. Quekett’s case the stomach outwardly was leaden-coloured and its vessels gorged with black blood; the intestinal peritonæum injected and speckled with fibrinous effusion; the villous coat of the stomach lined with yellow, curdled milk, and itself irregularly black here and there, as if charred, and in some places softened and corroded, so that a rent was made in handling it; the inner membrane of the duodenum similarly affected, and also even the jejunum, though more irregularly. The contents of the stomach were not acid, and did not contain any chloride.—In Mr. Crawfurd’s case the villous coat presented black elevated ridges, as if charred, and the furrows between were scarlet-red; black granular extravasation had taken place at many points into the submucous tissue; similar appearances were seen in the duodenum and jejunum; and the lower part of the gullet looked as if it had been cauterized.—In the case related by Orfila the gullet and pharynx were red, and at one or two places excoriated; the stomach inflamed externally, and its inner membrane spotted with gangrenous (?) patches, and very brittle; the duodenum thickened, and the jejunum perforated by a round worm.