sed,
and the temperature to which they were heated, Berthelot succeeded in
preparing mono-, di- and triglycerides of various fatty acids.

Practically all the oils and fats used in soap-making consist of
mixtures of these compounds of glycerol with fatty acids, which
invariably occur in nature in the form of triglycerides.

It was formerly considered that the three acid radicles in any naturally
occurring glyceride were identical, corresponding to the formula--

CH_{2}OR
|
CHOR
|
CH_{2}OR

where R denotes the acid radicle. Recent work, however, has shown the
existence of several so-called _mixed glycerides_, in which the
hydroxyls of the same molecule of glycerol are displaced by two or
sometimes three different acid radicles.

The first mixed glyceride to be discovered was oleodistearin,
C_{3}H_{5}(OC_{18}H_{35}O)(OC_{18}H_{35}O)_{2}, obtained by Heise in 1896
Mkani fat. Hansen has since found that tallow contains oleodipalmitin,
from C_{3}H_{5}(OC_{18}H_{35}O)(OC_{16}H_{31}O), stearodipalmitin,
C_{3}H_{5}(OC_{18}H_{35}O)(OC_{16}H_{31}O), oleopalmitostearin,
C_{3}H_{5}(OC_{18}H_{33}O)(OC_{16}H_{31}O)(OC_{18}H_{35}O) and
palmitodistearin, CH(OC_{16}H_{31}O)(OC_{18}H_{35}O)_{2}, the latter of
which has also been obtained by Kreis and Hafner from lard, while Holde
and Stange have shown that olive oil contains from 1 to 2 per cent. of
oleodidaturin, C_{3}H_{5}(OC_{18}H_{33}O)(OC_{17}H_{33}O)_{2}, and
Hehner and Mitchell have obtained indications of mixed glycerides in
linseed oil (which they consider contains a compound of glycerol with
two radicles of linolenic acid and one radicle of oleic acid), also in
cod-liver, cod, whale and shark oils.

In some cases the fatty acids are combined with other bases than
glycerol. As examples may be cited beeswax, containing myricin or
myricyl palmitate, and spermaceti, consisting chiefly of cetin or cetyl
palmitate, and herein lies the essential difference between fats and
waxes, but as these substances are not soap-making materials, though
sometimes admixed with soap to accomplish some special object, they do
not require further consideration.

The principal pure triglycerides, with their formulae and chief
constants, are given in the following table:--

[Transcriber's note: Table split to fit on page better.]

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Glyceride. | Formula.