The Physiomedical Dispensatory by William Cook, M.D., 1869
Lard is the fatty substance obtained from the hog, chiefly from the adipose tissue that abounds through the omentum and about the kidneys of that animal. The membranous substances are freed as much as possible from the adipose mass; and the latter is then cut into small pieces, washed to free it of all blood, and then put in an iron or other vessel with a small quantity of water. A gentle heat is then applied, and continued steadily till all the water has been evaporated and the lard has been freed from all the membranous substances. Several hours are required for this purpose, during which time the heat must not be raised too high. The lard in this state is a transparent fluid, with a peculiar unctuous odor. It may be freed from this odor (Amer. Jour. Pharm.) by adding to the adipose mass a small quantity of salt, continuing the heat till a scum rises, removing this carefully, and afterward freeing it from the salt. When sufficiently rendered, it is to be strained through linen.
Cold lard is white, soft, lighter than water, with little taste or smell, melting at 110E F., and insoluble in water. Alcohol dissolves a very little of it; ether and the volatile oils dissolve more; the stronger acids decompose it; and the alkalies unite with it chemically and form soaps. Melted lard readily unites with melted wax and resins. It contains nearly sixty-three percent of oleinthe fluid principle of oils; and about eighteen percent each of the more solid principles stearin and margarin. The application of a high steam pressure in closed iron tanks, is used in Cincinnati to separate the fluid from the solid constituentsthe former appearing in commerce as Lard Oil, and the latter being used extensively in the manufacture of candles. Nearly all the Glycerin of commerce is obtained from the soapmakers waste in the use of lard and tallow.
Pharmaceutical Uses: Lard is an emollient, and is sometimes used alone in frictions. Its chief use is as a soft vehicle in the preparation of ointments and cerates. It is occasionally smeared over the surface, previous to the application of a poultice, or added to a poultice to preserve its consistency. Light unction with it, as with other fixed oils, will relieve the too intense smarting of a stimulating application, and also of light burns, etc. It is often added to the resins to give pliancy to plasters; and is sometimes used as an addendum to laxative injections, especially when the lower bowel is irritable. The melting point of lard being above that at which an injection should be given, this fat will make an indifferent mixture for such purposes, and the fluid lard oil will be found more useful.
Lard containing salt or alum is unfit for pharmaceutical purposes. It may be purified from these by melting it with twice its weight of boiling water, and using thorough agitation. When cold: the fat can easily be lifted off from the water.
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