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NEUTRAL FATS. 233
abundantly. Besides these, oxyacids and high molecular alcohols have
been found in many plant fats. The extent to which traces of I
oxyacids occur in the animal kingdom has not been thoroughly inves-
tigated, but the occurrence of monoxystearic acid seems to have been
proved.1
The occurrence of high molecular alcohols, although ordinarily
only in small amounts, has on the contrary been positively shown in
animal fat.
The animal fats are of the greatest interest and consist of a mixture of
varying quantities of tristearin, tripalmitin, and triolein, having
an average elementary composition of C 76.5, H 12.0, and O 11.5 per
cent. It must be remarked that in animal fat (mutton and beef tallow)
as well as in plant fat (olive-oil) mixed triglycerides, such as dipalmityl-
olein, distearyl-palmitin and distearyl-olein, occur, and that these mixed
glycerides may also be prepared synthetically.2
Fats from different species of animals, and even from different parts
of the same animal, have an essentially different consistency, depending
upon the relative amounts of the different individual fats present. In
solid fats—as tallow—tristearin and tripalmitin are in excess, while
the less solid fats are characterized by a greater abundance of triolein.
This last-mentioned fat is found in greater quantities proportionally
in cold-blooded animals, and this accounts for the fact that the fat of
these animals remains fluid at temperatures at which the fat of warm-
blooded animals solidifies. Human fat from different organs and tissues
contains, in full numbers, 67-85 per cent triolein.3
The melting-point
of different fats depends upon the composition of the mixtures, and it
not only varies for fat from different tissues of the same animal, but also
for the fat from the same tissues in various kinds of animals.4
Neutral fats are colorless or yellowish, and, when perfectly pure,
ordorless and tasteless. They are lighter than water, on which they
float when in a molten condition. They are insoluble in water, dissolve
in boiling alcohol, but separate on cooling—often in crystals. They are
easily soluble in ether, benzene, chloroform, carbon disulphide and petro-
leum ether. The fluid neutral fats give an emulsion when shaken with
a solution of gum or albumin. With water alone they give an emulsion
1
Erben, Zeitschr. f. physiol. Chem., 30; Bernert, Arch, f . exp. Path. u. Pharm., 40.
2
Guth, Zeitschr. f. Biologie, 44; W. Hansen, Arch. f. Hygiene, 42; Holde and
Stange, Ber. d. d. chem. Gesellsch., 34; Kreis and Hafner, ibid., 36.
3
See Knopfelmacher, "Untersuch. iiber das Fett im Sauglingsalter," etc., Jarhbuch
f. Kinderheilkunde (X. F.), 45, which also contains the older literature; Jaeckle,
Zeitschr. f. physiol. Chem., 36.
4
According to Gilkin (Ber. d. d. chem. Gesellsch., 41) the fat from bone-marrow
and also other fats of animal and plant origin contain iron, which cannot be removed
by water containing hydrochloric acid.
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