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OLEIC ACID. 237
odorless oily liquid which solidifies in crystals at about 4° C, which
latter melt at 14° C. Oleic acid is insoluble in water, but dissolves
in alcohol, ether, chloroform and petroleum ether. With concentrated
sulphuric acid and some cane-sugar it gives a beautiful red or reddish-
violet liquid whose color is similar to that produced in Pettenkofer’s
test for bile-acids. If a solution of oleic acid in glacial acetic acid is treated
with a little chromic acid (in glacial acetic acid) and then with concen-
trated sulphuric acid, the green solution gradually becomes violet or
cherry-red, and shows two characteristic absorption bands in the green,
one a broad band near the blue and a second but fainter band near the
yellow (Lifschutz).1
The barium salt of oleic acid contains 19. G5 per
cent barium and the silver salt 27.73 per cent silver.
If the watery solution of the alkali compounds of oleic acid is pre-
cipitated with lead acetate, a white, tough, sticky mass of lead oleate is
obtained, which is not soluble in water and only slightly in alcohol, but is
soluble in ether. This salt is more easily soluble in benzene than the lead
salts of stearic and palmitic acids, and this behavior of the lead salts
toward ether and benzene is made use of in separating oleic acid from
the other fatty acids.
An acid related to oleic acid, doeglic acid, which is solid at 4° C, liquid at
16° C, and soluble in alcohol, is found in the blubber of the Balcena rostrata.
According to Bull this acid is probably only a mixture of oleic acid and another
acid
—
gadoleic acid, C^oH.-sOo, having a melting-point of +24.5° C, and occurring
in cod-liver oil, herring oil and in whale blubber. In addition to this acid Bull
found in cod-liver oil, besides myristic, palmitic, oleic and erucic acids, another
acid, having the formula CieEUCK. According to Ellmer 2
the most abundant
acid (80-90 per cent) in cod-liver oil is therapinic acid, Ci8 H2802 which is changed
into stearic acid by reduction and jecoleic acid, which seems to be identical with
Bull’s gadoleic acid. Kurbatoff has demonstrated the presence of linoleic
acid in the fat of the silurus, sturgeon, seal, and certain other animals. Drying
fats have also been found by Amthor and Zink 3
in hares, wild rabbits, wild
boar, and mountain-cock.
To detect the presence of fat in an animal fluid or tissue the fat must
first be shaken out or extracted with ether. After the evaporation of
the ether the residue is tested for fat and fatty acids. The neutral
fats are differentiated from the fatty acids by the acrolein test, and the
fatty acids by the fact that their solution in a mixture of alcohol and
ether has an acid reaction. In separating the fats from cholesterin
and other non-saponifiable substances, as well as for the determination
of the kind of the various fatty bodies, they are saponified with caustic
alkali, alcoholic potash, or with sodium alcoholate. In regard to these
operations, as well as the further investigation and the separation of the
1
Zeitschr. f. physiol. Chem., 56.
2
Bull, Ber. d. d. chem., Gesellsch., 39; Ellmer, Bioch. Zeitschr., 9.
3
Kurbatoff, Maly’s Jahresb., 22; Amthor and Zink, Zeitschr. f. anal. Chem., 36.
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