94 MILK AND DAIRY PRODUCTS PART 



2. Estimation of Lecithin. 



The older methods for determining the amount of lecithin in 

 milk were based upon the extraction of the lecithin with a mix- 

 ture of alcohol and ether, evaporation of the extract to dryness, 

 fusion with soda and saltpetre, estimation of the phosphoric acid 

 as magnesium pyrophosphate, and multiplication of the result 

 by 7*27. These methods, however, did not give reliable results, 

 for some of the phosphates in the milk were also extracted, and, 

 further, a part of the organic phosphorus was not oxidised during 

 fusion. The factor 7'27 is also unreliable, for the composition 

 of the lecithin of the milk is not perfectly understood. 



Bordas and Rackowski 1 have worked out a newer method for 

 the estimation of lecithin in milk, and it is easier and more 

 accurate than the older methods. The way in which it is carried 

 out is as follows : 100 c.c. of milk are dropped into a mixture 

 composed of: 



Alcohol (95 per cent.) 100 c.c. 



Water . . 100 



Acetic acid 10 drops. 



the whole being kept well stirred. In this way a coagulum 

 is obtained which can easily be separated by filtering. After 

 the nitrate has ceased to drop from the funnel, a piece of 

 rubber tubing provided with a pinchcock is drawn over the 

 tip of the funnel. Fifty c.c. of warm absolute alcohol are then 

 poured over the coagulum on the filter, allowed to stay there 

 two or three minutes, the mass being carefully stirred with a 

 platinum spatula, and then the pinchcock is opened and the 

 alcohol allowed to flow away. This process is repeated twice 

 more with 50 c.c. of alcohol, so that in all 150 c.c. of alcohol are 

 employed. 



The alcohol is distilled from the filtrate, and this is followed 

 by evaporation to dryness to get rid of the last traces of alcohol. 

 The residue which is left after the evaporation is extracted 

 with a mixture of equal parts of alcohol and ether, filtered, and 

 the filtrate evaporated on the water-bath to drive off the ether, 

 but not the alcohol. The alcoholic solution is then saponified 



1 Compt. rend, de I'Acad. des Sciences, Vol. CXXXIV, p. 1592. 



