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424 THE LIVER
namely from cholic acid, choleic acid and desoxycholic acid, and these
three acids are identically constructed in regard to their 19 carbon atoms.
The choloidanic acid is interesting in several respects. Panzer1
has obtained
from it by distillation with soda-lime, a hydrocarbon, CuHi6 , a homologue of
benzene, and on the oxidation of the cholic acid he has obtained an acid with the
formula, CgO^Os, which he considers as an oxyhexahydro-benzene-l-4-dicarboxylic
acid and from which he obtained paraoxybenzaldehyde. Pregl has obtained
from choloidanic acid, by heating, pyrocholoidanic acid, C15H20O4 which he con-
siders as parabcnzoic acid d-methyl-n-capric acid, and is produced from the
hexahydrobcnzene derivative by total dehydrogenation of a benzene derivative.
v. Furth and collaborators have investigated the products obtained on the
dry distillation of cholic acid at ordinary pressure, and Wieland and Weil 2
on
such distillation in vacuum. In the first case chiefly hydrocarbons with 12 to
17 carbon atoms were obtained, and in the second instance chiefly an unsaturated
acid, C24H34O2, was obtained, and in both cases these products and their double
bindings have been carefully investigated. We must wait for further developments
in these investigations before we attempt to draw any positive conclusions from
them.
From the investigations on the cholic acids carried out thus far we
are not able to draw any positive conclusions on their constitution, but
that they are derivatives of hexahydrobenzene, is very probable for sev-
eral reasons.
Cholic acid crystallizes partly in rhombic plates or prisms with one
molecule of water, and partly in larger rhombic tetrahedra or octahedra
with one molecule of alcohol of crystallization (Mtlius). These crystals
quickly become opaque and porcelain-white in the air. They are quite
insoluble in water (in 4000 parts cold and 750 parts boiling), rather
soluble in alcohol, but soluble with difficulty in ether. The amorphous
cholic acid is less insoluble. The solutions have a bitter-sweetish taste.
The crystals lose their alcohol of crystallization only after a lengthy
heating to 100-120° C. The acid free from water and alcohol melts at
195-196° C. According to Bondi and Muller the melting-point of the
perfectly pure acid is 198° C. It forms a characteristic blue compound
with iodine (Mylius). If finely powdered cholic acid is added to 25
per cent hydrochloric acid at the ordinary temperature, a beautiful violet-
blue coloration gradually appears, and this color is permanent for some
time and then becomes gradually green and yellow. The blue solution
shows an absorption band in the neighborhood of the D line (Hammar-
sten 3
)
.
The alkali salts are readily soluble in water, but when treated with a
concentrated caustic or carbonated alkali solution, they may then be
1
Panzer, Zeitschr. f. physiol. Chem., 48 and 60.
2
v. Furth with Link, Bioch. Zeitschr., 26, with Ishihara, ibid., 43; Wieland and
Weil, Zeitschr. f. physiol. Chem., 80.
3
Zeitschr. f. physiol. Chem., 61.
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