YOLK AND WHITE OF THE EGG. 153 



funnel, some more water added, and the mixture extracted 

 with ether. Separate the , aqueous solution containing 

 barium chloride, and wash the ether extract several times 

 with water. The ether leaves, on evaporating, fatty acids 

 (in regard to the methods of identifying these see chapter on 

 Adipose Tissue, page 144). 



The solution E is freed from the excess of barium hydrox- 

 ide by passing in carbon dioxide and filtering from the barium 

 carbonate. The filtrate contains glycerin, glycerin-phos- 

 phoric acid, and choline. It is evaporated on the water-bath 

 as completely as possible. To show the presence of the 

 glycerin-phosphoric acid, C 3 H 5 (OH) 2 P0 4 H 2 , grind a part of 

 this residue with several times its volume of the oxidizing 

 mixture, heat in a crucible till fused, and show the presence 

 of phosphoric acid in the fused mass by means of ammonium 

 molybdate (see chapter on Milk, page 9). Since barium 

 phosphate is insoluble in water, the detection of phosphoric 

 acid in this case proves the presence of an acid containing 

 phosphorus, which forms a soluble barium salt. Such an 

 acid is glycerin-phosphoric acid. 



TT/~\/"^TT 



To detect the choline, * \ 2 NOH, extract the 



greater part of the residue resulting from the evaporation 

 of solution E with absolute alcohol, 1 precipitate the solution 

 with platinum chloride, filter off the precipitate, wash with 

 alcohol, and crystallize the choline platinum chloride from 

 water. This crystallizes in large orange-red prisms or hex- 

 agonal plates. 



The residue F is freed from ether by grinding in a mortar 



1 Barium glycerin-phosphate remains undissolved, but a considerable 

 portion of the glycerin-phosphoric acid always passes into solution, pre- 

 sumably as choline glycerin-phosphate, as the choline acts like ammonium 

 carbonate in the presence of carbonic acid, i.e., it precipitates barium 

 carbonate from the barium glycerin-phosphate. 



