given edible oil from olive oil. If, however, any given edible oil be mixed with olive oil in small proportions not exceeding 25 to 30 percent, even the skilled taster will be deceived. In such cases only the chemist who has much skill and practice is able to detect the adulteration.
Adulteration with Cottonseed Oil.—In the United States the principal adulteration of olive oil is with cottonseed oil. This is an oil which has already been described as of high nutritive value and to which no objection can be made from any hygienic or dietetic point of view. It is made in great quantities in the United States, and when subjected to the most careful refining processes can be offered to the consumer at a price probably not greater than one-fifth that of high-grade olive oil. It becomes the ideal material with which to adulterate olive oil. This adulteration extends often to complete substitution, the oil in question, though represented as olive oil both by the dealer and the label, containing no trace whatever of that substance. Such bare-faced substitution has apparently almost passed away under the quickening ethical sense of the manufacturer and merchant and the character of the national and state laws. Many of the oils which are used to adulterate olive oil have a greater specific gravity, hence whenever the specific gravity of an olive oil at 15 degrees goes above .917 it is ground for suspicion of adulteration though by no means a positive proof. The presence of cottonseed oil in olive oil is easily detected by the Halphen test, which has already been described. In Europe a very common method of adulteration is with sesamé oil, the properties of which are described below. Peanut oil is also extensively used for the same purpose. These two oils are easily detected when mixed with olive oil. The sesamé oil is distinguished by the color reaction to be described. Peanut oil is distinguished by the saponification of the oil, separation of the fatty acids, and consequent crystallization of the arachidic acid, which produces a crystalline form which is readily recognized by an expert. Rapeseed oil and poppy-*seed oil are also extensively used as adulterants in Europe, but not very extensively in this country. Nearly all the oils which are employed in the adulteration of olive oil have high iodin numbers, and therefore whenever an iodin number is above 89 or 90 it may be regarded as a suspicious circumstance. There are, however, many genuine olive oils which would be condemned as adulterated if this test alone were employed. In addition to the oils mentioned, small quantities of castor oil, lard oil, fish oil, and even of petroleum oil, have been found as adulterants in olive oil. These, however, occur very infrequently, and it is not likely that they have been employed in this country.
If the examination shows that a given sample is free of cottonseed, sesamé, and peanut oil, and other characteristics in the sample are those of olive oil, it may be safely accepted as a pure sample.
Color of Olive Oil.—The color of the freshly expressed olive oil is usually green or dark from the chlorophyl and other coloring matter derived from
