Page:Foods and their adulteration; origin, manufacture, and composition of food products; description of common adulterations, food standards, and national food laws and regulations (IA foodstheiradulte02wile).pdf/444

 more that of almond oil than that of olive oil. Some of this oil is doubtless mixed with olive oil when the pulp and kernel of the olive are pressed together, but the quantity thus secured is not very great and does not introduce into the substance anything which gives a specific reaction. It is by no means as high a grade of oil as that expressed from the flesh of the olive alone.

Peanut Oil.—Peanut oil is the refined expressed oil of the peanut, prepared in the manner above described, and is highly valued as a table or salad oil and, unfortunately, is used very often as an adulterant of olive oil, the mixture being sold under the name of the more valuable of its constituents.

Peanut oil contains arachidic acid, which in combination with glycerine forms one of the constituents which serves to distinguish it particularly from other edible oils. There is no other edible oil which contains arachidic acid in sufficient quantities to lead to any mistake concerning its relationship to peanut oil.

Renard's Test for Peanut Oil as Modified by Tolman.—Place 20 grams of oil in an Erlenmeyer flask. Saponify with alcoholic potash, neutralize exactly with dilute acetic acid, using phenolphthalein as indicator, and wash into a 500 c.c. flask containing a boiling mixture of 100 c.c. of water and 120 c.c. of a 20 percent lead acetate solution. Boil for a minute, and then cool the precipitated soap by immersing the flask in water, occasionally giving it a whirling motion to cause the soap to stick to the sides of the flask. After the flask has cooled, the water and excess of lead can be poured off and the soap washed with cold water and with 90 percent (by volume) alcohol. Now add 200 c.c. of ether, cork the flask, and allow to stand for some time until the soap is disintegrated, then heat on the water bath, using a reflux condenser, and boil for about five minutes. In the oils most of the soap will be dissolved, while in lards, which contain so much stearin, part will be left undissolved. Cool the ether solution of soap down to from 15° to 17° C., and let stand until all the insoluble soaps have crystallized out—about twelve hours are required.

Filter and thoroughly wash the precipitate with ether. Save the filtrate for the determination of the iodin number of the liquid fatty acids by the Muter method. The soaps on the filter are washed back into the flask by means of a stream of hot water acidified with hydrochloric acid. Add an excess of dilute hydrochloric acid, partially fill the flask with hot water, and heat until fatty acids form a clear, oily layer. Fill the flask with hot water, allow the fatty acids to harden and separate from the precipitated lead chlorid; wash, drain, repeat washing with hot water, and dissolve the fatty acids in 100 c.c. of boiling 90 percent (by volume) alcohol. Cool down to 15° C., shaking thoroughly to aid crystallization. From 5 to 10 percent of peanut oil can be detected by this method, as it effects a complete separation of the soluble acid from the insoluble, which interferes with the crystallization of the arachidic acid. Filter, wash the precipitate twice with 10 c.c. of 90 percent (by volume) alcohol,