Eschar, s. A hard crust or scar made by hot applications.

Escharotic, a. Caustic, having the power to sear or burn the flesh.

Escharotics are generally in the form of powder. Such are nitric oxide of mercury (red precipitate), exsiccated sulphate of alumine (burnt alum), acetate of copper (crystallised verdigris), sulphate of copper (blue vitriol). These are applied, either separately, or two or more of them are mixed together, and finely powdered; sometimes they are mixed with bole armeniac or chalk, by which they are rendered milder, or with lard or digestive ointment.

ESCHAROTIC POWDERS.
No. 1.Exsiccated or burnt alum2 dr.
Nitric oxide of mercury½ oz.—Mix.
No. 2.Sulphate of copper1 oz.
Bole Armeniac1 oz.—Mix.
No. 3.Acetate of copper1 oz.
Burnt alum2 dr.—Mix.

See Caustics, Astringents, Digestives, and Detergents.

ESCHAROTIC LINIMENT.
Honey8 oz.
Muriatic acid1 oz.
Verdigris1 oz.
Mix over a slow fire.

This liniment may be made stronger by substituting nitrous acid for muriatic, or by retaining the muriatic, and substituting for the verdigris one drachm of sublimate. A weaker liniment is made, and a very useful one, by using two ounces of vinegar instead of the muriatic acid. (See Egyptiacum). Escharotics are applied to foul ulcers, and are employed to destroy fungous or proud flesh.—White.

Esculent, s. Something fit for food.

Essence, s. In medicine, the chief properties or virtues of any simple, or composition, collected into a narrow compass. Essence of mustard, composed of camphor, oil of rosemary, and oil of turpentine, is a good stimulating embrocation.

Essential, a. Necessary; important in the highest degree, principal; pure, highly rectified. Essential oils are obtained by distillation from mint, pennyroyal, peppermint, lavender, caraway seeds, anise-seeds, juniper berries, lemon-peel, sandal-wood, &c.