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236 ANIMAL FATS AND PHOSPHATIDES.
CH3
Palmitic acid, (CHo)i4, crystallizes from an alcoholic solution in tufts
COOH
of fine needles. It melts at 61° C.;1
still the admixture with stearic acid,
essentially changes them elting- and solidifying-points according to th
relative amounts of the two acids. Palmitic acid is somewhat more
soluble in cold alcohol than stearic acid; but they have about the same
solubility in boiling alcohol, ether, chloroform, and benzene. Its barium
salt contains 21.17 per cent barium, and silver salt contains 29.72 per
cent silver.
CH2.O.C18H33O
Olein, or triolein, C57Hi04O6, = CH.O.Ci8H33 O, is present in all animal
CH2.O.C18H33O
fats, and in greater quantities in vegetable fats. It is a solvent for
stearin and palmitin. The oleic acid (elaic acid), C18H34O2, as soaps,
probably has about the same occurrence as the other fatty acids.
Olein is, at ordinary temperatures, a nearly colorless oil of a specific
gravity of 0.914, without odor or marked taste, and solidifies in crystalline
needles at -6° C. It becomes rancid quickly if exposed to the air. It
dissolves with difficulty in cold alcohol, but more easily in warm alcohol
or in ether. It is converted into its isomer, elaidin, by nitrous acid.
CH3
(CH2) 7
r*vx
Oleic acid, =,„, is an unsaturated acid of the series CnH„-202, and
(CH2) 7
COOH
correspondingly takes up two halogen atoms, i.e., iodine, at the double
bondage, a factor which is the basis of v. Hubl’s method for determining
the iodine equivalent. On taking up hydrogen, which can be accomplished
by heating with hydroiodic acid and amorphous phosphorus, it is trans-
formed into the corresponding saturated acid, namely, stearic acid. On
oxidation the double bonds are satisfied by 2HO groups, and dioxystearic
acid, CH3(CH2)7CHOH.CHOH(CH2 )7COOH, is formed. Oleic acid
readily undergoes oxidation in the air with the formation of acid products,
and the occurrence of monoxystearic acid, found in animal fats in certain
instances, can be explained by this oxidation. Oleic acid on heating
yields, besides volatile fatty acids, sebacic acid, C10H18O4, which melts
at 127°C; and with nitrous acid it is transformed into its isomer, solid
elaidic acid, which melts at 45° C.
Oleic acid forms at ordinary temperature a colorless, tasteless, and
1
Carlinfanti and Levi-Malvano. Chem. Centralbl. 1910.
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