354 PRINCIPLES OF AGRICULTURAL CHEMISTRY 



Lecithins. These are wax-like bodies which resemble fats in 

 some respects. They contain nitrogen and phosphorus. Like 

 fats, they are saponified by alkalies. When saponified they yield 

 a soap, cholin, phosphoric acid, and glycerol. The quantity of 

 lecithin in the ether extract is calculated from the amount of 

 phosphoric acid found in it. The magnesium pyrophosphate 

 multiplied by 7.25 is assumed to represent the lecithin. Calcium 

 and magnesium phosphates have, however, been found in the ether 

 extract of plants, their presence being attributed to the presence of 

 metallic glycero-phosphates soluble in ether. When these sub- 

 stances are present, the amount of lecithin in the fat is less than 

 the amount calculated from the phosphoric acid present. 



Lecithin is not entirely extracted by ether from plant substance, 

 but is completely extracted when the ether extraction is followed 

 by extraction with absolute alcohol. If the alcoholic solution is 

 evaporated at 40-50 C. and the residue taken up with ether and 

 purified by shaking with water, the lecithin can be obtained fairly 

 pure. 



Leguminous seeds are relatively rich in lecithin; the cereals 

 (wheat, rye, and corn) contain much less. The table below shows 

 the lecithin content of some substances: 



LECITHIN IN PLANTS. 



Per cent, 

 in dry matter 



Young grass 0.45 



Young vetch plants 0.86 



Yellow lupine seeds 1.55 



Soja bean i .64 



Peas 1.23 



Wheat 0.65 



Rye 0.57 



Corn 0.74 



Sunflowers 0.44 



Vetch 0.98 



The alcoholic extract contains not only lecithin, but other 

 organic compounds containing phosphorus, some of which con- 

 tain sugar. Lecithin is of considerable value to the animal and 



