LIQUID HYDROCHLORIC ACID.

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suspects that bromine may be present, partly because this substance hasbeen found in common salt, and partly because a small quantity of thissubstance gives a yellow colour to pure hydrochloric acid.

The presence of iron is shewn by saturating the acid with carbonateof soda, and then applying tincture of nutgalls, which produces a blacktint. Another mode is to supersaturate the liquid with ammonia or itssesquicarbonate, by which the red or sesquioxide of iron will be pre-cipitated.

If the liquid acid contain either free chlorine (or bromine ) it will pos-sess the power of dissolving leaf-gold, or even of decolourizing a smallquantity of sulphate of indigo. A solution of protochloride of tin pro-duces a purplish colour with a solution of gold.

Sulphuric acid (free or combined) may be detected by adding to thesuspected acid a solution of chloride of barium: if sulphuric acid bepresent, a heavy white precipitate of sulphate of baryta is procured,which is insoluble in both acids and alkalies. In applying this test thesuspected acid should be previously diluted with five or six times itsvolume of water; otherwise a fallacy may arise from the crystallizationof the chloride of barium.

Physiological effects. —(a.) On dead animal matter. —Very dilutehydrochloric acid, mixed with dried mucous membrane, has the pro-pertv of dissolving various animal substances (as coagulated albumen,fibrin of the blood, boiled meat, &c.), and of effecting a kind of artificialdigestion of them, somewhat analogous to the natural digestive process—(Muller, Elements of Physiology, p. 544).

(b.) On living animals. —The effects of liquid hydrochloric acid onliving animals (horses and dogs) have been investigated by Sproegel,Courton, Viborg (Wibmer, die Wirkung der Arzneimittel und Gifte), andby Orfila {Toxicologic Generate). Thrown into the veins it coagulatesthe blood, and causes speedy' death. Small quantities, however, may beinjected without giving rise to fatal results. Thus Viborg found that ahorse recovered in three hours from the effects of a drachm of the aciddiluted with two ounces of water, thrown into a vein. Administeredby the stomach to dogs, the undiluted acid acts as a powerful causticpoison. Exhalations of the acid vapours take place through the mouthand nostrils, and death is generally preceded by violent convulsions.

(c.) On man. —Properly diluted, and administered in small but repeateddoses, hydrochloric acid produces the usual effects of a mineral acidbefore described (pp. 80, 81, and 84): hence it is tonic, refrigerant, anddiuretic. It usually causes a sensation of warmth in the stomach, relaxesthe bowels, and increases the frequency of the pulse. Larger dosesare said to have excited giddiness and a slight degree of intoxication orstupor. In a concentrated form it operates as a powerfully caustic poison.The only recorded case of poisoning by it (in the human subject) withwhich I am acquainted, is that mentioned by Orfila ( Toxicolog. Generate).The particular nature of the chemical changes effected by it in the organictissues with which it comes in contact, is not so well understood as inthe case of sulphuric or nitric acid. Its chemical action is less energeticthan either of the acids just mentioned.

Uses — {a.) Internal or remote. —Hydrochloric acid has been employedin those diseases formerly supposed to be connected with a putrescentcondition of the fluids; as the so-called putrid and petechial fevers,