Sevum Praeparatum, B.P. Prepared Suet.
Prepared suet consists of the internal fat of the abdomen of the sheep, Ovis aries, Lion. (Order Ungulata), prepared by cutting the fresh omentum into pieces, crushing the pieces so as to break the membranous vesicles in which the fat is enclosed, then melting and straining. The purified fat should be stirred while cooling, to prevent the separation of constituents of high melting-point in a more or less granular form. Purified suet is also official in the U.S.P. It occurs as a white, almost odourless, solid fat, with a bland taste. Melting-point, 45° to 50°, congealing between 37° and 40°. Tallow is nearly white when freshly rendered, free from disagreeable odour, and almost tasteless. It contains the following mixed glycerides:—Oleodipalmitin, stearodipalmitin, oleopalmitostearin, and palmitostearin. Tallow is less rich in stearin than mutton suet; it is used in the preparation of surgical shaving cream (Cremor ad Rasendum).
Insoluble in water or alcohol; soluble in boiling alcohol (1 in 44), ether (1 in 60), or petroleum benzin (1 in 2), from which solution crystals separate on standing. The alcoholic solution should be neutral, or only slightly acid.
Constituents.—The chief constituents of suet are stearin and palmitin, about 70 to 80 per cent. of which are present, together with about 20 to 30 per cent. of olein. Prepared suet should be used instead of lard in preparing ointments and plasters for native use in India. It should be kept in well-stoppered bottles, as on prolonged exposure to air it becomes rancid, and unfit for use.
Uses.—Prepared suet is used in the preparation of Unguentum Hydrargyri, and is a convenient solvent of phosphorus and salicylic acid (see Sevum Phosphoratum and Sevum Salicylatum).