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 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. 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.

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