46 FATS, OILS, AND WAXES 



Lecithin is readily hydrolysed by boiling with alkalis, 

 notably baryta, and is also broken up by lipase, and, less 

 readily, by mineral acids. The products of its hydrolysis are 

 glycero-phosphoric acid : 



CHoOHCHOHCHoOP = (OH), 



O 



choline HON(CH3)3CHoCH20H and fatty acids ; a similar 

 hydrolysis takes place in the germinating seed.* 



Originally it was considered that the fatty acids of lecithin 

 were either stearic, palmitic, or oleic, but it has been found 

 that the iodine values of the acids obtained from lecithin are 

 much higher than would be given by these acids alone. 



CHOLINE. 



To examine the products of the hydrolysis of lecithin, this 

 substance is heated with a solution of barium hydrate in ex- 

 cess ; a baryta soap is formed, which may be filtered off. The 

 aqueous solution contains barium glycero-phosphate and cho- 

 line ; the latter may be extracted as follows.f 



Treat the solution with a stream of carbon dioxide until no 

 more barium carbonate comes down. Filter and evaporate 

 the filtrate to dryness. Treat the residue with absolute alcohol, 

 which will dissolve the choline but not the barium glycero- 

 phosphate. The alcoholic solution, if treated with an alcoholic 

 solution of platinic chloride, gives a precipitate of the double 

 platinichloride of choline. 



Green and Jackson | give the following method : Allow the 

 finely divided material to stand for some days under absolute 

 alcohol. Pour off the extract, and evaporate to dryness ; the 

 residue is again extracted with absolute alcohol, and finally 

 with a mixture of alcohol and ether. These extracts are 

 mixed, and the solvents evaporated off. The choline is con- 

 tained in the residue. The following tests may be i em ployed 

 for its detection : — 



I. Boil a strong aqueous solution; decomposition ensues 



*Schulze: " Z. physiol. Chem.," 1887, 11, 365; Schulze and Frankfurt: 

 " Ber. deut. chem. Gesells.," 1893, 26, 2151. 



t Leathes: " The Fats," " Monographs of Biochemistry," London, 1910. 

 J Green and Jackson: " Proc. Roy. Soc, Lond.," B., 1906, 77, 6g. 



