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TAUROCHOLIC ACID. 421
by the salts of the heavy metals, but also by the salts of barium, cal-
cium and magnesium.
The principle in the preparation of the pure glycocholic acids con-
sists in treating a 2-’.\ per cent solution of bile free from mucus, when
rich in glycocholic acid (so-called Hefner’s bile l
), with ether, and then
with 2 per cent hydrochloric acid. If the bile is not directly precipitable
with hydrochloric acid (bile relatively poor in glycocholic acid), then
precipitate the chief mass of the glycocholic acid with ferric chloride,
or better with lead acetate, decompose the precipitate with soda and treat
the 2 per cent solution as above stated with ether and hydrochloric acid.
The crystalline and washed mass is boiled with water, and on cooling
glycocholic acid crystallizes out, and then this is recrystallized from
water or from alcohol by the addition of water. The residue that remains
after boiling in water (paraglycocholic acid and glycocholeic acid) is
converted into their barium salts, and after a complicated method (see
Wahlgren) the glycocholeic acid is obtained. The reader is referred to
more exhaustive works for other methods of preparation.
Hyoglycocholic Acid, C27H43NO5, is the crystalline glycocholic acid obtained
from the bile of the pig. It is very insoluble in water. The alkali salts, whose
solutions have an intensely bitter taste, without any sweetish after-taste, are
precipitated by CaCb, BaCl2 ,
and MgCl2 , and may be salted out like a soap by
Na2 S04 when added in sufficient quantity. According to Piettre it can be salted
out entirely, free from sulphur, by caustic alkali which is not possible by other
methods. By precipitation with NaCl in such quantity that the precipitate re-
dissolves on warming, Hammarsten 2
obtained the alkali salt, as macroscopic
crystals, on cooling. Besides this acid there occurs in the bile of the pig still
another glycocholic acid (Jolin 3
).
The glycocholate in the bile of rodents is also precipitated by the above
mentioned earthy salts, but cannot, like the corresponding salt in human or ox-
bile, be directly precipitated on saturating with a neutral salt (Na2S04 ). Guano
bile-acid possibly belongs to the glycocholic-acid group, and is found in Peruvian
guano, but has not been thoroughly studied.
Taurocholic Acid. This acid, which is found in the bile of man, car-
nivora, oxen, and a few other herbivora, such as sheep and goats, has the
constitution C26H45NSO7. On boiling with acids and alkalies it splits
into cholic acid and taurine. Taurocholic acid has also been prepared
synthetically by Bondi and Muller, using the same method as they used
for glycocholic acid.
Taurocholic acid can be readily obtained, by the method suggested
by Hammarsten,4
as groups of fine needles or as beautiful prisms on
slow crystallization. The crystals do not change in the air, but they
decompose above 100°. They are soluble in alcohol but insoluble in
1
Hiifner, Journ. f. prakt. Chfem. (N. F.i, 10, 10, and 25.
2
Not published. M. Piettre, Recherches sur la bile, Laval, 1910.
3
Zeitschr. f. physiol. Chem., 12 and 13.
1
Ibid., 43.
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