Adeps Lanae Hydrosus (U. S. P.)—Hydrous Wool-Fat.
The purified fat of the wool of sheep (Ovis Aries, Linné; class Mammalia; order Ruminantia), mixed with not more than 30 per cent of water"—(U. S. P.).
SYNONYM: Purified wool-fat.
Source and Preparation.—Sheep's wool contains about 45 per cent of a fat known as suint, which must be removed from it before it can be made into fabric. This fat, which was formerly known and used as aesypum, contains a variable amount of potash, probably from 15 to 35 per cent. Suint is obtained by evaporating to dryness, wool-washings; and by proper chemical manipulation, the potassium salts, combined with organic acids taken from the soil by the animal while grazing, and eliminated in the perspiration and adhering to the wool, are separated; and it is estimated that thousands of tons of potash are yearly produced from this source alone. When first prepared, wool-fat consists of about one-third fatty acids in a free condition, besides certain fatty-acid ethers of cholesterin and glycerol. It is the cholesterin fats that enter into the commercial wool-fat. The process for making lanolin is secret. It has a characteristic, wool-like odor, is of a yellow-brown color, and though but partially dissolved by alcohol, dissolves readily in acetone, ether, chloroform and benzol. If this anhydrous wool-fat be now mixed, by kneading, with water, not more than 30 per cent, it forms the Pharmacopoeial hydrous wool fat, or Adeps lanae hydrosus.
Description and Tests.—"A yellowish-white or nearly white, ointment-like mass, having a faint, peculiar odor. Insoluble in water, but miscible with twice its weight of the latter, without losing its ointment-like character. With ether or chloroform, it yields turbid solutions which are neutral to litmus paper. Hydrous wool-fat melts at about 40° C. (104° F.). When heated on a water-bath, it finally leaves a residue amounting to not less than 70 per cent, which is transparent while melted, and, when cold, appears as a yellow, tough, unctuous mass, completely soluble in ether or chloroform, and only partially soluble in alcohol. A solution (1 in 50) of a portion of this mass in chloroform, when poured on the surface of concentrated sulphuric acid, gradually develops a deep-brown color at the line of contact of the two layers. When a portion of this mass is ignited, it should not leave more than 0.3 per cent of ash, which should not have an alkaline reaction on litmus (absence of alkalies). If 2 Gm. of the same mass are dissolved in 10 Cc. of ether, and mixed with 2 drops of phenolphtalein T.S., a colorless liquid results (absence of free alkalies), which should be decidedly reddened by 1 drop of normal potassium hydrate V. S. (absence of free fatty acids). If 10 Gm. of hydrous wool-fat be heated, together with 50 Cc. of water, on a water-bath, until the fat is melted, there should result an upper, translucent and light-yellow, fatty layer, and a lower, clear, aqueous layer, which latter should not yield glycerin upon evaporation, and, when a portion of it is heated with some potassium or sodium hydrate T.S., it should not emit vapors of ammonia"—(U. S. P.).
Chemical Composition.—Wool-fat is a mixture mainly composed of ethers of fatty acids, with cholesterin instead of glycerin as the basis.
Action and Medical Uses.—The use of sheep's wool-fat is ancient and accounts of such employment are handed down by Pliny in his Natural History. It was reintroduced as a therapeutic agent by Liebreich, in 1885. It is employed as a non-irritating and efficient ointment base, and possesses marked advantages over like bodies in that it may be mixed with aqueous mixtures and glycerin. It will take up double its weight of water and of glycerin. Lanolin does not become rancid, nor does it leave the skin as soft and pliable as some emollient agents. Much contention has been had as to whether it is absorbed by the skin more than other fats, and as to whether it has any superiority in causing the absorption of drugs by the skin. Stellwagon, Liebreich, and others believe it to be absorbed more rapidly than an other fat. As it is a sebaceous secretion, it undoubtedly tends to favor normal action of the skin. It has been preferred alone as a protective in mild affections of the skin, and as an unguent for massage. As a vehicle for salicylic acid, boric acid, iodine and the iodides, and a number of other agents, it has been largely employed in a great variety of cutaneous affections.
Related Product.—THILANIN. Thilanine, Sulphurated lanolin, contains sulphur to the extent of 3 per cent. It is prepared by acting upon anhydrous wool-fat with sulphur, aided by heat. It has the consistence of hydrous wool fat, being a yellow-brown, unctuous body. It has been employed as a non-irritating dermic medicament. It is recommended for acute and subacute eczema of the face, scaly eczema of the extremities, and for the papulo-vesicular variety affecting the hands, as well as for other eczematous eruptions. Sycosis, acne, herpes, psoriasis, and dermatitis resulting from chrysarobin, are said to have been benefited by it. It is said to be particularly useful in itching conditions. It should be diluted with water or oils when applied to the scalp.