CHEMICAL BASIS OF Till; ANIMAL BODY. 211 



}u.'t water in which they are soluble, separating out again as their 

 solution cools. 1 



The acid crystallises in fine glistening needles. which require 

 about 300 parts of c..ld hut only li!0 ..f hot water for their solu- 

 tion. They are also very soluble in alcohol, hut practically in- 

 snluhlc in ether. The salts ut' tliis acid, more especially those 

 with tin- alkalis, an- extremely soluble e-ven in c..ld water. also 

 in alcohol, but very slightly BO if at all in ether. I'.oth tip 

 acid and its salts are dextro-rotatory: for the former, in alcoholic 

 solutions, (a) D = +29-0, for the latter (a) D =+L ) .V7 < llppe- 

 Sevl.-r). (llycocholic acid is a compound of cholalic a .-id and 

 gly< -in ( glycocoll) or amido-acetic a. id. When boiled with hy- 

 orolysing agenta such as dilute acids or alkalis it takes up one 

 molecule of water and is resolved into its components: 



Cholalic acid. 



, 4- H 8 = <JH 2 (NH,) COOH + C^H^O,. 



It is thus analogous in constitution to hippuric acid, in which 

 glycin is similarly united to henzoic acid. 



If di-s,,l\,..l in concentrated sulphuric acid and then \vanm-d. 

 cholic acid l>v tin- n-niiival \ one mlrcule "t" \vati-r yii-ld> iilyi-'u-li 

 acid. C.j.-.HuNn.. Tin- l-ariiiin >alt nf this la->t acid is iii>>ltil>li- in 

 . which fact is nf importance. >ince cholmiic acid j -.early 



tin- .-aim- -1'i-rilic rotatory power a^ <;1\ coeliolic acid. 



I Taurocholic acid. II \ 



This acid is foun<l to some extent in ox-hile, and is more ]>len- 

 tifully present in that of man. The bile of the dog Contains 

 tanroeholic acid alom-, unmixed with 



n rntinii. The. method de-crihcd ahove suflices to obtain 

 olvcocholic acid free from tanroeholic. On the other hand it is 

 not l.v any means easy to ol.tain the hitter free from the former, 



iirocholic acid is extremely soluhlr in water (its crystals are 

 deliqiieNi-ent) and this solution can readily dissolve the much l-s 

 readilv solnlde olycocholjc acid. Hence the mother liquor from 



lycocholic acid crv-taN contains not merely the tauroch<ilic 

 acid but some of the former acid also. This difficulty is avoided 

 by employing as a source for its preparation dog*bil6 in which 

 there is no glycocholic acid. Tin- bile is treated a.s ah 

 scribed down to the stage at which the taurocholate ,,f soda is 

 precipitated from its alcoholic .solution by an excess of ether. 

 The precipitate is now dissolved in water and the acid precip, 

 as a lead salt by tin- addition of ammonia and /'.-/ "tate. 



f i.tlic-r nictliixU -Mini- -JM <-ial work nhouM i.-li M 



Hopp*' - in ll rm:im>'- / I'/iytioi. 



Hd. v .1 i : MUius. /*. f.fkftU. Chrm. Hit. xi. (1887). S. 331 



