No matter how carefully a fat was purified, it may happen that the pomades made from it, if kept long in stock, may subsequently become rancid—a circumstance which may destroy the reputation of a factory. Fortunately we know two substances which materially counteract the tendency of fats to become rancid: salicylic acid and benzoin. Either of these substances is added to many perfumery articles, especially pomades, in order to prevent rancidity; an admixture of from one-one-thousandth to five-one-thousandths parts of solid salicylic acid suffices, according to our experiments, for the purpose; of benzoin we need about three-fourths of an ounce for every quart of fat; the resin is only partly soluble in fat, but imparts to it its vanilla-like odor. For the finest pomades sublimed benzoic acid is used, in the proportion of about 150 to 240 grains to the quart of fat. CHAPTER XXIII. FORMULAS FOR THE MANUFACTURE OF POMADES AND HAIR OILS. A. Pomades. In manufacturing perfumery two groups of pomades are distinguished—those with a hard base, and those with a soft base. By base is meant the fat which is the vehicle of the odor in every pomade. The consistence of the substance depends upon its melting-point; lard and beef marrow, having a low melting-point, furnish soft pomades; while beef and mutton tallow, which often receive an addition of paraffin, wax, or spermaceti in order to make them firmer, have a higher melting-point and serve for hard pomades. French perfumers put on the market some very fine pomades consisting of the fat which has served for the absorption of odors by maceration, enfleurage, etc., and which has been treated with alcohol for the extraction of the odors (so-called washed pomades). No matter how long such a fat is treated with alcohol, it tenaciously retains a portion of the odor to which the great fragrance of these pomades is due and which has given them their reputation. If the pomades resulting from the following formulas should turn out too soft—a fact depending on the climate of the place of manufacture—they may receive an addition of a mixture of equal parts of paraffin, wax, and spermaceti, in portions of respectively five per cent at each addition, until the desired ointment-like consistence is attained. CANTHARIDAL POMADE. Beef marrow 4 lb. Wax 7 oz. Oil of mace 150 grains. Oil of clove 150 grains. Oil of rose 150 grains. Tincture of cantharides ¾ oz. Tincture of cantharides is prepared by prolonged maceration of ¾ ounce of powdered cantharides in one quart of alcohol. CIRCASSIAN POMADE. Benzoin pomade (see below) 2 lb. Rose pomade 1 lb. Lard 2 lb. Expressed oil of almond 4 lb. Alkanet root 3½ oz. Oil of rose ½ oz.