SAPONIFIABLE OILS, FATS AND WAXES

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cyl palmitate occurs in beeswax. It is an ester of palmitic acid
and myricyl alcohol, CsoHeiOH. Ceryl cerotate is the chief
constituent of Chinese wax. It is an ester of cerotic acid,
C25H_5iCOOH, and ceryl alcohol. The most important aromatic
alcohols occurring in waxes are the isomeric alcohols cholesterol
and phytosterol, C26H_43OH. These are found as esters of
palmitic, stearic and oleic acids.
Separation and Identification.—Notwithstanding the differ-
ences in composition the task of separating and determining the
per cent of different oils in a mixture is a difficult and sometimes
impossible one, because of the fact that the same general com-
pounds constitute the greater proportion of all fats and oils.
The chemist must usually be satisfied if he can recognize single
oils or, with the nature of a single oil known, determine the
approximate extent and nature of adulteration. The differences
in molecular weight and degree of saturation, the presence and
per cent of free alcohols or acids and the occasional occurrence
of traces of unusual substances, characteristic of certain oils,
constitute the bases of the tests used in the effort to identify an
oil. The examination becomes therefore not an analysis, in the
usual sense, but a series of tests applied in order to gain informa-
tion regarding the identity of a pure oil and, so far as is possible,
the composition of a mixture. Certain physical and chemical
"constants" are determined and compared with the constants
obtained from examination of oils of known purity. The chief
obstacle to the use of such figures lies in the fact that, for a given
kind of oil they are actually variable within certain limits. These
limits may be very narrow, but it sometimes happens that the
ranges for two or more oils overlap. Thus olive oil from Italy is
not chemically identical with olive oil from California. The soil,
climate, variety of plant and method of expressing from the
olive have their influence upon the properties of the various
glycerides and other substances present in the oil. It is only
when the ranges of variation for different oils do not overlap that
it is easy to determine the identity of a single oil, although it
usually happens that while overlapping occurs with a single con-
stant it does not occur with others.
The significance of the various constants and their methods of
determination will be described.

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