SECTION I. 



FATS, OILS, AND WAXES. 



In ordinary parlance, no clear distinction is made in the use 

 of the terms fat and wax, which are applied more or less in- 

 discriminately to any solid substances which have a greasy 

 feeline to the touch and do not mix with water. Chemically, 

 however, there is a marked difference between the two classes ; 

 the fats are compounds of the trihydric alcohol glycerol, 

 whereas the waxes are compounds of the higher monohydric 

 alcohols, such as cetyl alcohol CigHggOH, myristic alcohol 

 CgoHfiiOH, and cholesterol C27H45OH. 



The tendency to rely on physical properties only, and to 

 regard waxes as having generally a harder consistency than 

 fats has given rise to several cases of incorrect nomenclature. 

 For example, wool fat and sperm^aceti being compounds of 

 cholesterol and cetyl alcohol are in reality waxes, though they 

 are usually regarded as fats, whereas the substance ordinarily 

 known as Japan wax is actually a fat, since it is a compound 

 of glycerol. 



The term oil, as used in the ordinary sense to imply a 

 liquid which is immiscible with water, must not be taken to 

 have any chemical significance, since substances having this 

 physical property are found in almost every class of chemical 

 compound. Used in connection with fats, the term oil simply 

 implies a fat that is liquid at ordinary temperatures ; any solid 

 fat on melting becomes an oil, and, on the other hand, any 

 fatty oil on solidifying becomes a fat. 



OCCURRENCE. 

 Fats are very widely distributed in the vegetable kingdom, 

 and occur in both vegetative and reproductive structures ; m 

 fact, it is highly probable that all living cells contain a certain 



I 



