326 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



acid is precipitated but redissolves giving a cherry- red, then a purple solution, 

 which becomes bluer in shade on keeping. The purple solution shows an 

 absorption band between D and E. 



Reactions (3) and (4) are given by other compounds and are not dis- 

 tinctive for cholalic acid. 



Properties of Choleic Acid. C2 4 H 40 O 4 ? 



Choleic acid crysatllises from alcohol in bundles of flat needles which 

 melt at 185-190. It is soluble with difficulty in water, more easily in ether 

 and readily in absolute alcohol, but less so than cholalic acid. It is dextro- 

 rotatory. On oxidation it yields dehydrocholeic acid, cholanic acid. 



Properties of Deoxycholic Acid. C 24 H 40 O 4 . 



It melts at 172-173 and has [a] D 20 + 57*02. 



Glycocholic Acid. C 26 H 43 O 6 N. 



C 23 H 39s- co Glycocholic acid is present in ox and 



NH CH 2 .COOH. human bile (7-9 per cent), but not in that 

 of carnivora. It is converted by hydrolysis with acids into cholalic 

 acid and glycine, and has been synthesised. 



Preparation. 



(1) Huf net's Method. 



Fresh ox bile is covered with a layer of ether in a measuring cylinder and 

 treated with concentrated hydrochloric acid (2 c.c. to 40 c.c. bile). The 

 turbidity at first formed becomes crystalline. The ether is poured off, the 

 mass stirred with water, well shaken, filtered and washed with cold water till 

 the washings are colourless. The precipitate is purified as given in Ham- 

 marsten's method. 



(2) Plattners Method. 



Bile is evaporated to a syrup and extracted with alcohol. The solution is 

 decolorised by boiling with charcoal, some of the alcohol is distilled off and 

 the concentrated alcoholic solution is precipitated with ether. The precipitate 

 becomes crystalline on standing from a few hours to some da*ys and consists 

 of sodium glycocholate, glycocholeate and taurocholate (Plattner's crystallised 

 bile). The crystals are dissolved in water, some ether and then dilute 

 sulphuric acid are added until there is a permanent cloudiness. A mass of 

 fine shining needles fills the solution. They are filtered off and washed free 

 from acid with water. The mixture of acids is separated by Hammarsten's 

 method. 



