OCCURRENCE OF LECITHINS 45 



PHYSICAL AND CHEMICAL PROPERTIES OF WAXES. 



Waxes are soluble in all the ordinary fat solvents such as 

 benzene, ether, chloroform, etc., though they are rather less 

 soluble than the fats. 



Being free from glycerides the waxes, when heated, give 

 no smell of acrolein ; they do not become rancid like the fats, 

 and are less easily hydrolysed, but they can be decomposed 

 by prolonged heating with alcoholic potash. 



FURTHER REFERENCE. 



Lewkowitsch : " Chemical Technology and Analysis of Oils, Fats, and 

 Waxes," London, 1915. 



LIPOIDS. 



Closely related to the fats is the group of substances known 

 as phosphatides, phospholipins or lecithins, the last name being 

 derived from the Greek Xe/a#o?, meaning egg yolk, from which 

 substance the first representative of the class was prepared. 



The name phosphatide was first given by Thudichum to 

 a number of substances containing phosphorus which he 

 obtained from brain. Subsequently Overton introduced the 

 term lipoid to represent a group of substances occurring in 

 the animal tissues which resembled fats in their solubilities. 

 Leathes uses the term phospholipins, in place of phosphatides, 

 to denote compounds of fatty acids containing phosphorus and 

 nitrogen, and proposes the name of lipins for compounds of 

 fatty acids that contain nitrogen but no phosphorus.* 



OCCURRENCE. 



Lecithin compounds occur in the grains of cereals, in the 

 seeds of several Leguminosae, Rzcinus, and species of Pinus ; 

 in the leaves of Castanea, and in Fungi ; they are also widely 

 distributed in animals. In fact, these substances are stated to 

 occur in small quantities in all living cells, and they appear to 

 be more especially abundant where fats occur. Zlataroff con- 

 siders that light is requisite for the formation of lecithins since 

 he finds that the amount present in seeds increases during 

 germination in the light.f 



* The nomenclature of this group of substances is considered by Maclean : 

 "Lecithin and Allied Substances. The Lipins," London, 1918 

 t Zlataroff: " Biochem. Zeit.," 1916, 75, 200. 



