Melt over a water-bath and add

Powdered catechu

Leave on the fire, stir briskly, and, when the mass has consistency enough, remove it from the fire and add

Run on an oiled marble, and spread with a brush. When the paste is cold, rub it with tissue paper moisten it slightly, and cover it with silver leaf. Dry and cut into lozenges.

Mucilage of tragacanth in sufficient quantity to

make the whole into a stiff mass.

Pass the whole several times through a fine sieve.

SECTION XIII.

FATTY SUBSTANCES USED IN PERFUMERY.

THE fatty substances used in perfumery are of two kinds the greases, and the fixed oils.

The greases are solid, soft, or concrete, and are found in the meshes of the cellular or adipose tissue of various animals. The greases are insoluble in water, and lighter than that liquid; inflammable when sufficiently heated; when exposed to the air and light, they become rancid by absorbing a large portion of oxygen, and are thus transformed into acid. All greases are colorless when pure; in an impure state they differ in color-some are white, as those of pork, sheep, calf, etc.; some are yellow, as butter, etc. Greases differ also in odor, consistency, and fusibility; the odor is very weak in tallow and lard, strong and disagreeable in the bear and goat. Generally, greases from carnivorous animals have not much consistency, whilst those from herbivorous animals are more solid. Their solubility is variable, either as they are obtained from animals of different species, or from different parts of the same animal, or of animals of the same species which have sud

denly died or have been affected by long-continued disease. The fusibility of greases varies from 80° to 140°, depending upon their immediate coinposition.

Until 1831, fatty substances were considered as pure immediate principles, differing from each other only in their physical properties; about that time, MM. Chevreul and Braconnot ascertained that fatty substances are mixtures of several peculiar principles, amongst which margarin, stearin, and olein are the most remarkable.

Greases, especially lard and mutton suet, melted with olive oil, are the bases of many pomades, cosmetics, soaps, etc.

Animal greases by time become rancid, and give to the products into the composition of which they enter irritating and sometimes toxical properties.

The greases thus changed, treated by boiling alcohol, leave, after evaporation, a brown residuum having a nauseous taste. This residuum has sometimes poisoned animals.

Greases are adulterated with feculæ, cooked potatoes, kaolin, powdered chalk, etc. All these impurities may be detected by ether, which dissolves only the pure grease. By boiling the suspected grease in ten times its weight of water, all the impurities are precipitated, whilst it floats on the surface.

The oils are liquid, unctuous, and inflammable,