296 CBEMISTBY OF THE PTOMAINS. 



cess of free acid with carbonate of sodium, is evaporated. The 

 residue is extracted with alcohol, and the alcoholic solution is pre- 

 cipitated with alcoholic mercuric chlorid. The precipitate thus ob- 

 tained, on recrystallization several times from a large quantity of 

 boiling water, yields the pure double salt of cholin. 



If desirable, it can be made from pure lecithin, best prepared ac- 

 cording to Gilson's method. Yolk of eggs is repeatedly shaken up 

 with ether until the latter is colored only a faint yellow ; the ether 

 solution then distilled, the residue taken up in petroleum ether and 

 filtered. The filtrate, in a separatory funnel, is well shaken with 75 

 per cent, alcohol, and this is repeated several times with fresh alco- 

 hol. The alcoholic extracts are combined, allowed to stand for some 

 time, then filtered and subjected to distillation to remove traces of 

 petroleum ether. The solution is now set aside in a cool place for 

 several days ; the precipitate which forms consists of cholesterin, etc., 

 and a little lecithin. The alcoholic solution is filtered by decanta- 

 tion, then decolored by boiling with bone-black and rapidly evaporated 

 at 50°— 60° to a syrupy consistency. This residue is extracted with 

 ether, the solution filtered and evaporated. The lecithin thus ob- 

 tained is almost perfectly pure but contains traces of cholesterin. 

 To purify it completely, it can be dissolved in as little absolute 

 alcohol as possible and set aside to precipitate in the cold (5°— 15°). 



Cholin may be prepared synthetically according to the method of 

 Wurtz (see Gulewitsch, Zeitschr. f. physiol. Ghem., 24, 514) or of 

 Hofmann and Bode. In the latter ethylene bromid is heated with 

 excess of alcoholic trimethylamin. The resulting bromin compound 

 is treated with silver nitrate, filtered, and the filtrate heated on the 

 water-bath for about eight days yields cholin nitrate. This is the 

 easiest and cheapest method of preparation. It may be prepared 

 from neurin (p. 290). 



In regard to the genesis of cholin the preponderance of testimony 

 goes to show that it is derived from the decomposition of lecithin 

 which, according to the researches of Diakonow and others, is one 

 of the most widely distributed compounds occurring in greater or 

 less quantity in all of the animal tissues. Lecithin which is a com- 

 plex ester, decomposes under the action of acids and alkalis into a 

 base (cholin), glycerin, phosphoric acid and fatty acids (stearic, oleic, 

 palmitic, etc.). Gilson has shown that dilute sulphuric acid slowly 

 decomposes lecithin, forming cholin which, after a few days, disap- 

 pears ; on the other hand sodium hydrate, in even 1 per cent, solu- 

 tion, rapidly decomposes it. This change is undoubtedly accom- 

 plished in a similar manner through the agency of bacteria. Brieger 

 (II., 17) is inclined to believe that cholin exists preformed in the 

 various tissues inasmuch as he has been unable to obtain it from the 

 brain, which is rich in lecithin, by boiling with 2 per cent, hydro- 

 chloric acid. (See Schulze, page 298.) Prolonged heating with 



