PROPERTIES 9 



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 O-poo to 0-970 at 15°. 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 : — 



CH3COOC2H5 + H2O = CH3COOH + C2H5OH . . (i) 

 Ethyl acetate Acetic acid Ethyl alcohol 

 CH3CN + 2H2O = CH3COOH + NH3 . . . (2) 



Methyl cyanide 

 CaHjCONHCHXOOH + H,0 = CgHjCOOH + NH^CHjCOOH . (3) 

 Hippuric acid Benzoic acid Glycine 



Ci2H,,0,i + HP = 2CeHi,Oe . . . . (4) 



Malt sugar Glucose 



C,oH„NO„ + 2HaO = CjHjCHO + 2CeHi208 + HCN . (5) 

 Amygdalin Benzalde- Glucose Hydro- 



hyde cyanic acid 



It will be seen from reaction (l) that the conversion of an 

 ester into an acid and an alcohol is an example of hydrolysis, 

 and since fats are esters it follows that they also must be 

 capable of hydrolysis. 



The reaction — 



Ci,H35COOCH2 CH2OH 



C17H35COOCH H- 3H2O = sCi.HjsCOOH + CHOK 



C^Hg^COOCH^ CH2OH 



Stearic acid Glycerol 



