CHAPTER VII 



FATS AND ALLIED SUBSTANCES 



A FAT may be defined as an ester or glyceride of a fatty acid. Just 

 as an inorganic salt, such as sodium chloride, is formed by the reaction 

 of hydrochloric acid with sodium hydroxide, so a fat is formed by the 

 reaction of the trihydric alcohol, glycerol, and a fatty acid. 



The word fat is not a familiar one in botanical literature, the term 

 oil being more commonly used. It is generally met with in connexion 

 with the reserve products of seeds. The oils of seeds are, however, true 

 fats. The term oil may be misleading to some extent, because a fat 

 which is liquid at ordinary temperatures is usually spoken of as an oil, 

 and yet there are also many other substances, of widely differing chemi- 

 cal composition, which have the physical properties of oils, and which are 

 known as such. 



Most of the vegetable fats are liquid at ordinary temperatures but 

 some are solids. 



The best-known series of acids from which fats are formed is the 

 series CnHgnOa of which formic acid is the first member. The other 

 members of the series are: 



Formic acid 

 ^ Acetic acid 



Propionic acid 

 ^ Butyric acid 



Valeric acid 

 1 Caproic acid 



(Enanthylic acid 

 1 Caprylic acid 



Pelargonic acid 

 ^ Capric acid 



Undecylic acid 

 1 Laurie acid 



Tridecylic acid 



H-COOH 



CH3-C00H 



CaHs-COOH 



CsHr-COOH 



C4H,-C00H 



C5Hn • COOH 



CeHis-COOH 



C7H15 • COOH 



CgHn-COOH 



CgHig-COOH 



CioHgi-COOH 

 CnHsa'COOH 

 CiaHae-COOH 



1 Myristic acid 

 Isocetic acid 



1 Palmitic acid 

 Daturic acid 



1 Stearic acid 

 Nonadecylic acid 



1 Arachidic acid 



1 Behenic acid 



2 Lignoceric acid] 

 2 Carnaiibic acidj 



Hyaenic acid 

 2 Cerotic acid 

 2 Melissic acid 



C13H27 • 

 G14H29 

 CisHsi 



C17H35 

 C18H37 



C19H39 

 C21H43 



C23H47 



C24H49 

 C25H61 

 CtMriKQ 



COOH 

 COOH 

 COOH 

 COOH 

 COOH 

 COOH 

 COOH 

 COOH 



COOH 



COOH 

 COOH 

 COOH 



1 Occur in fats. 



Occur in waxes. 



