12 FATS, OILS, AND WAXES 



hydrous salts such as sodium sulphate, depends on the fact 

 that the anhydrous salt when ground up with the moist tissue 

 withdraws the water from it, forming the hydrated crystals. 

 In a few hours the substance is sufficiently dry to be powdered 

 The chief objection to this process is the fact that a considerable 

 bulk of salt has to be employed and consequently the volume 

 of the material to be extracted is much increased. 



PHYSICAL PROPERTIES >OF FATS. 



The naturally occurring fats vary in consistency from oils 

 to wax-like solids ; the solid fats have mostly a low melting 

 point which is, however, rarely a sharp one, as natural fats 

 are not simple substances, but are, as a rule, mixtures of 

 several different chemical individuals ; such mixtures never 

 have sharp melting points. 



. All fats and fatty oils are lighter than water, their specific 

 gravity varying from about 0*900 to O'9/o at 1 5. They are 

 insoluble in water and at ordinary temperatures are sparingly 

 soluble in cold alcohol, excepting castor oil which dissolves 

 readily in this solvent ; they, however, dissolve readily in 

 ether, chloroform, petroleum ether, benzene, carbon tetra- 

 chloride or carbon disulphide. 



CHEMICAL PROPERTIES OF FATS. 



One of the most important chemical properties of fats is 

 their decomposition by hydrolysis. 



The term hydrolysis, which literally means loosening by 

 water, is applied to any reaction in which a substance is broken 

 up into two or more simpler ones with the fixation of water. 



The following examples taken from a variety of different 

 classes of compounds all illustrate this reaction : 



