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CHOLESTERIN. 447
soluble in boiling alcohol, and crystallizes on cooling. It dissolves readily
in’ether, chloroform, and benzene, and also in the volatile or fatty oils.
It is dissolved to a slight extent by alkali salts of the bile-acids, better
in the presence of oleic soap (Gerard l
). The solutions in ether and
chloroform are levorotatory, (a) D = —31.12° (2 per cent ethereal solu-
tion).
Among the many compounds of cholesterin the propionic ester
C2H5.CO.O.C27H45 is of special interest because of the behavior of the
fused compound on cooling, and it is used in the detection of choles-
terin. For the detection of cholesterin use is made of its reaction with
concentrated sulphuric acid, which gives colored products.
If a mixture of five parts sulphuric acid and one part water acts on
cholesterin crystals, they show colored rings, first a bright carmine-red
and then violet. This test is employed in the microscopic detection
of cholesterin. Another test, and one very good for the microscopical
detection of cholesterin, consists in treating the crystals first with the
above dilute acid and then with some iodine solution. The crystals
will be gradually colored violet, bluish-green, and a beautiful blue.
Salkowski’s 2 Reaction. The cholesterin is dissolved in chloroform
and then treated with an equal volume of concentrated sulphuric acid.
The cholesterin solution becomes first bluish-red, then gradually more
violet-red, while the sulphuric acid appears dark red with a greenish
fluorescence. If the chloroform solution is poured into a porcelain dish
it becomes violet, then green, and finally yellow.
Liebermann-Burchard’s 3
Reaction. Dissolve the cholesterin in
about 2 cc. chloroform and add first 10 drops of acetic anhydride and then
concentrated sulphuric acid drop by drop. The color of the mixture
will first be a beautiful red, then blue, and finally, if not too much
cholesterin or sulphuric acid is present, a permanent green. In the pres-
ence of very little cholesterin the green color may appear immediately.
Neuberg-Rauchwerger’s 4
Reaction. With rhamnose, or better still
with 6-methylfurfurol and concentrated sulphuric acid, an alcoholic
solution of cholesterin gives a pink ring, or after mixing the liquids and
cooling, a pink solution. On proper dilution an absorption-band can
be seen just beginning before E and whose other side coincides with b.
This reaction is of interest because it is also given by bile-acids, some
camphor derivatives, abietinic acid, and a hydride of retene.
1
Compt. rend. soc. biol., 58.
2
Pfluger’s Arch., 6.
3
C. Liebermann, Ber. d. deutsch. chem. Gesellsch., 18; 1804, H. Burchard, Bei-
trage zur Kenntnis der Cholesterine, Rostock, 1899.
4
Salkowski’s Festschrift, 1904.
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