FATS AND OILS. WAXES. LECITHINS OR 



LIPINS. 



Fats and oils are present as reserve food material in most animal 

 and vegetable tissues. They are the esters of the higher fatty acids, 

 especially palmitic, stearic and oleic acids, with glycerol. All these 

 glyceryl esters have similar names in which the name of the fatty acid 

 describes the nature of the fat, e.g. butyrin, caproin, palmitin, olein. 



CH 2 0-OC . C 17 H 38 



Cl 



CH 2 OC . C 17 H 35 

 Stearin. 



There is no chemical distinction between oils and fats ; the solid esters 

 are fats, the liquid esters are oils. The consistency of a fat or oil de- 

 pends upon the nature of its constituents. Beef and mutton tallow 

 which are hard solids contain chiefly palmitin and stearin. Lard and 

 human fat which are soft solids contain more olein. Palm oil consists 

 principally of palmitin. The vegetable oils, such as olive, cotton seed 

 and linseed oils contain chiefly olein or other esters of unsaturated acids. 



Fats are economically of great value as food, as illuminating agents, 

 as lubricating agents, for soap making and for other purposes. 



Waxes, which in appearance somewhat resemble fats, are chemically 

 very different They are esters of the higher alcohols, cetyl alcohol, 

 C 16 H 33 OH, myristic alcohol, C 3o H 6l OH, and cholesterol, C 27 H 45 OH, with 

 the higher fatty acids, e.g. carnauba wax contains ceryl and myricyl 

 alcohols and cerotic and carnaubic acids ; wool wax or lanolin contains 

 cholesterol ; spermaceti is the palmitic acid ester of cetyl alcohol. 



Lecithins are present in all animal and vegetable cells and accom- 

 pany the fat, but are intimately associated with the life processes, ex- 

 isting in loose combination with protein. Lecithin has the composition 

 and properties of a fat, but contains in addition phosphoric acid and 

 choline (p. 127), 



CH 2 O OC . R CH 2 O OC . R 



CHO OC . R' CHO OC . R' 



/0CH 2 . CH 2 . N(CH 3 ) 3 OH ,O . CH 2 . CH 3 . NH 2 



CH 2 OP^ CH 3 OP( 



\OH \OH 



Lecithin. Kephalin ? 



Kephalin has a similar'composition but contains amino-ethyl alcohol 

 in the place of choline. These two lipins are generally found to- 

 gether in most tissues and are difficult to separate. They both 

 contain a saturated acid and an unsaturated acid. About 10 per cent, 

 of lecithin is present in egg yolk ; liver and blood contain about 2 per 

 cent. , vegetable tissues from -25 to i-? percent 



