YOLK AND WHITE OF THE EGG. 151 



Shake vigoror Jy the yolks of ten hen's eggs in a flask or in 

 a wide-necked separating-funnel with two to three times their 

 volume of ether and draw off the yellow-colored ether solution 

 as soon as it has thoroughly separated. If this separation does 

 not take place readily, add a little alcohol. Filter the ether 

 solution through a dry filter and repeat the extraction with 

 fresh portions of ether until the ether has only a faint yellow 

 color. The amount of ether used may be considerably 

 lessened if the successive ether extracts are distilled and the 

 distilled ether used over again. A small portion of the first 

 ether extract is reserved for the reactions. 



The main quantity of the ether extract A is distilled, the 

 residue, while still hot, is removed from the flask to an evapo- 

 rating-dish, preferably an enameled iron dish, the flask rinsed 

 with small quantities of ether, and the ether removed by 

 evaporation on the water-bath. Boil the residue persist- 

 ently with 50 g. of crystallized barium hydroxide and 400 cc. 

 of water, replacing from time to time the water which evapo- 

 rates. In this process the fat is split up into fatty acids, 

 which form insoluble barium soaps, and glycerin; the lecithin 

 into fatty acids (barium soaps), glycerin-phosphoric acid, and 

 choline. 



The complete saponification is attained with difficulty and yet it 

 is very desirable for the further work. It is best to remove from the 

 aqueous fluid the sticky lumps of barium soaps which separate and 

 which contain much undecomposed substance, extract them with ether, 

 evaporate the ether extract, and boil the residue again with barium 

 hydroxide solution. The decomposition is complete when a portion 

 of the ether extract of the barium soaps, after evaporating the ether, 

 no longer gives the acrolem reaction (see chapter on Adipose Tissue, 

 page 142). 



Finally the barium soaps are removed from the aqueous 

 fluid by filtration and washed. 



The crude barium soap B is freed from water as far as 



