SAPONIFIABLE OILS, FATS AND WAXES 193
stituent which gives the color apparently is assimilated by the animal
without change.
A negative result does not prove the absence of cotton seed oil because
heating the oil for 10 minutes at 250° renders it incapable of giving the color.
Sesame Oil: Baudouin Test.—Dissolve 0.1 gm of finely powdered
sugar in 10 cc of hydrochloric acid (specific gravity 1.20), add 20 cc of the
oil to be tested, shake thoroughly for a minute, and allow to stand. The
aqueous solution separates almost at once. In the presence of even a very
small admixture of sesame oil this is colored crimson. Some olive oils give a
slight pink coloration with this reagent, but they are not hard to distinguish
if comparative tests with sesame oil are made.
Arachis (Peanut) Oil.—The constants of arachis oil are almost
identical with those of olive oil and the difficulties involved in
detecting admixtures of the two are correspondingly great. The
Renard test for arachis oil is based upon the isolation and weigh-
ing of the small amount (about 5 per cent) of arachidic acid
(C2oH4oOs) that occurs as its glyceride in arachis oil. The
method must be carried out with great care or stearic acid
(CigHseOs), whose solubility is not far from that of arachidic acid,
will be obtained and mistaken for the latter. The Renard
method is fully described elsewhere.1
Soybean Oil.—This oil is increasing very much in importance
as a commercial product, on account of the large increase in
production of soybeans for food products and for feeding to
farm animals. The oil possesses drying properties, having an
iodine absorption number of about 136, which is not far from
that of linseed oil. For this reason soybean oil is used to some
extent as an adulterant of linseed and china-wood oils. It is
used also very largely in the manufacture of butter substitutes
and of high-grade soaps.
A modification of Settings test2 has been given by Newhall.3
This is performed as follows:
Add 5 cc of chloroform to 5 cc of the oil in a test-tube, then add a
few drops of a solution of gum Arabic and 5 cc of a 2-per cent solution
of uranium nitrate or acetate. Shake vigorously to form an emulsion.
Soybean oil will give a characteristic lemon-yellow emulsion, while other
oils will give only faint yellow or brown.
1 Assoc. Off. Agr. Chemists, ''Methods of Analysis," 253; MAHIN, "Quan-
titative Analysis," 2nd Ed., 383.
2 Chem. Abstr., 7, 908 (1913). '
3 J. Ind. Eng. Chem., 12, 1174 (1920).
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