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PALMIT IN. 235
tions in gangrene of the lungs, and in cheesy tuberculous masses. It
occurs as lime soap in excrement and adipocere, and in this last product
also as an ammonium soap. It also exists as alkali soap in the blood,
bile, transudations and pus, and in the urine to a slight extent.
Stearin is the hardest and most insoluble of the three ordinary neutral
fats. It is nearly insoluble in cold alcohol, and soluble with great dif-
ficulty in cold ether (225 parts). It separates from warm alcohol on
cooling as rectangular, and less frequently as rhombic plates. The opinions
regarding the melting-point are somewhat varied. Pure stearin, ac-
cording to Heintz, 1
melts transitorily at 55° and permanently at 71.5°.
The stearin from the fatty tissues (not pure) melts at 63° C.
CH3
Stearic acid, (CH2 )i6, crystallizes (on cooling from boiling alcohol) in
COOH
large, shining, long rhombic scales or plates. It is less soluble than the
other fatty acids and melts at 68.2° C.2
Its barium salt contains 19.49
per cent barium, and its silver salt contains 27.59 per cent silver.
CH2 .O.C 16H3 iO
Palmitin, or tripalmitin, C5iH9s06 ,
= CH.O.Ci6H31 0. Of the two solid
CH2 .O.Ci6H3 iO
varieties of fats, palmitin is the one which occurs in predominant quan-
tities in human fat (Langer 3
). Palmitin is present in all animal fats
and in several kinds of vegetable fat. A mixture of stearin and palmitin
was formerly called margarin. As to the occurrence of palmitic acid,
C16H32O2, about the same remarks apply as to stearic acid. The mixture
of these two acids has been called margaric acid, and this mixture occurs
—often as very long, thin, crystalline plates—in old pus, in expectora-
tions from gangrene of the lungs, etc.
Palmitin crystallizes, on cooling from a warm saturated solution in
ether or alcohol, in starry rosettes of fine needles. The mixture of pal-
mitin and stearin, called margarin, crystallizes, on cooling from a solu-
tion, as balls or round masses which consist of short or long, thin plates
or needles which often appear like blades of grass. Palmitin, like stearin,
has a variable melting- and solidifying-point, depending upon the way it
has been previously treated. The melting-point is often given as 62° C,
but some investigators 4
claim that it melts at 50.5° C, solidifies on
further heating, and melts again at 66.5° C.
1
Annal. d. Chem. u. Pharm., 92.
2
According to Carlinfanti and Levi-Malvano, Chem. Centralbl., 1910.
3
Monatshefte f. Chem., 2; see also Jaeckle, Zeitschr. f. physiol. Chem., 36.
* R. Benedikt, Analyse der Fette, 3. Aufl., 1897, p. 44.
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