ACETIC ACID.

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or other metallic matter. Acrid substances, such as capsicums, grains ofparadise, &c. are sometimes added to vinegar to increase its pungency.They are discovered by carefully saturating the vinegar with potash, andthen tasting the solution with attention.

The strength of the acetic acid is ascertained by determining itssaturating power. One hundred grains of the officinal acid shouldsaturate 87 grains of crystallized carbonate of soda, or dissolve about 30grains of white marble (carbonate of lime), One hundred grains ofdistilled vinegar should saturate 13 grains of crystallized carbonate ofsoda, or dissolve about 4|- grains of white marble.

If sulphuric acid be present, a white precipitate is produced by theaddition of acetate of lead or chloride of barium. Hydrochloric acid isdetected by the white precipitate (chloride of silver) caused with nitrateof silver. The presence of nitric acid is known by immersing a piece ofsilver in the suspected acetic acid : if nitric acid be present, nitrate ofsilver would be formed, which might be recognized by the subsequentaddition of hydrochloric acid.

Lead, copper, or tin, would be recognized by the precipitate producedby hydrosulphuric acid or ammonia. If lead be present, the iodide ofpotassium would throw down a yellow precipitate of iodide of lead.

Physiological Effects. —Before proceeding to notice the operationof acetic acid on vegetables and animals, it may be useful to point outsuch of its effects on dead organic matters as have reference to the influ-ence of this substance on living beings. In the first place, it is a well-known and powerful antiseptic, and is employed, partly on this account,in the ordinary operation of pickling, and in the preservation of animalfood, and of anatomical preparations. The impure acetic acid obtainedin the distillation of wood, acts more efficaciously in this respect than thepure acid, on account of the creosote which it contains. Secondly, theaction of acetic acid on albumen, fibrin, and the sanguineous particles,deserves especial notice. Liquid albumen (as the serum of the blood,and the white of egg) is not coagulated by the ordinary acetic acid of theshops. Coagulated albumen is readily dissolved by it with the evolutionof nitrogen, especially with the assistance of heat. Fibrin , as muscle orthe crassamentum of the blood, also dissolve in it: the solution, byevaporation, yields a gelatiniform mass. Caseuin is coagulated by it.It changes the form of the red particles of frog’s blood, and dissolves partof the red colouring matter (Muller’s Physiology , p. 106). It is anexcellent solvent of gelatine. Diluted and mixed with mucus, it acts asa digestive fluid (Muller, op. cit., p. 545).

(a) . On vegetables. —Distilled vinegar is ranked, by Achard, amongvegetable poisons (Decandolle, Phys. Veget.).

(b) . On animals generally. —According to Orfila ( Journ. Chim. Med.t. vii. p. 449) concentrated acetic acid acts as a caustic poison to dogs.It causes blackening of the mucous lining of the stomach, analogous tothat produced by sulphuric acid. The same authority tells us that fouror five oimces of common vinegar prove fatal to dogs in ten or fifteenhours, if vomiting be prevented by the oesophagus. Injected into theveins, vinegar does not appear to act very energetically. Yiborg threwtwo ounces and a half of wine vinegar into the jugular vein of a horse :the next day the animal was well (Wibmer, Wirkung d. Arzneim.)