Recent years, however, have made us acquainted with a substance which in very minute quantities—one-half of one per cent of the mass to be preserved by it—prevents decomposition and rancidity of fats. This is salicylic acid, a chemical product which, being harmless, tasteless, and odorless, should be employed wherever we wish to guard against destructive influences exerted by air, fermentation, etc. While formerly all emulsions were made only in small amounts, just sufficient for several weeks’ use, salicylic acid enables us to manufacture larger quantities at once and to keep them without much fear of their spoiling. However, even the presence of salicylic acid is no guaranty against deterioration, if other precautions are neglected. The products should be kept in well-stoppered bottles or vessels, in a cool and dark place. All substances cannot be preserved by salicylic acid, and there are certain ferments or fungi which resist the action of salicylic acid. If chloroform is not objectionable in any of these preparations—and only so much is necessary as can be held in actual _solution_ by the liquid, on an average three drops to the ounce—this preservative is preferable to salicylic acid. The only fats used in the preparation of emulsions are expressed oil of almonds, olive oil, and lard. Almond oil is best made by immediate pressure of the bruised fruits, since fresh almond meal likewise finds application in perfumery; olive oil and lard must be very carefully purified. This is done by heating them for one hour with about ten times the quantity of water containing soap (one per cent of the quantity of fat to be purified). They are then treated five or six times with pure warm water until the latter escapes quite neutral. If the water turns red litmus paper blue, it would indicate the presence of free alkali (soap); if it turns blue litmus paper red, it would prove the presence of free fatty acids (rancid fat). Either one of these substances, especially the latter, would injure the quality of the product. The fat should be absolutely neutral and have no influence on either kind of litmus paper; then its quality may be pronounced perfect. CHAPTER XXI. FORMULAS FOR THE PREPARATION OF EMULSIONS, MEALS, PASTES, VEGETABLE MILK, AND COLD-CREAMS. A. Emulsions. AMANDINE. _Almond Cream._—Melt ten pounds of purified lard in an enamelled iron pot or a porcelain vessel, and while increasing the temperature add little by little five pounds of potash lye of 25% strength, stirring all the time with a broad spatula. When fat and lye have become a uniform mass, 2¾ to 3½ ounces of alcohol is gradually added, whereby the mixture acquires a translucent, crystalline appearance. Before the alcohol is added three-fourths to one ounce of oil of bitter almond is dissolved in it. The soapy mass thus obtained is called “almond cream” (crême d’amandes) and may be used alone for washing. For making Amandine take of—