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 2-3 per cent solution of bile free from mucus, when 

 rich in glycocholic acid (so-called HUFNER'S bile x ), 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, C 2 7H 43 N0 5 , 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 CaCl 2 , BaCl 2 , and MgCl 2 , and may be salted out like a soap by 

 Na 2 S0 4 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 (Na 2 S0 4 ). 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 C26H4sNS07. 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. Chem. (N. F.), 10, 19, and 25. 



2 Not published. M. Piettre, Recherches sur la bile, Laval, 1910. 



3 Zeitschr. f. physiol. Chem., 12 and 13. 



4 Ibid., 43. 



