CHAPTER VI. 

 THE FATS. 



THE TRUE FATS. 



The true fats are compounds, or Esters of the fatty acids with the 

 triatornic alcohol glycerol. 1 Thus tripalmitin is formed by the union 

 of three molecules of palmitic acid with one molecule of glycerol and 

 the elimination of a corresponding number of molecules of water. 



CH 2 OH HOOC.Ci 5 H 31 CH 2 OOC.C 15 H 3 i 



CHOH + HOOC.C 15 H 3 i = CH.OOC.CuHn + 3H 2 O 



CH 2 OH HOOC.C 15 H 3 i CH 2 OOC.Ci 5 H3i 



By the action of alkalies this process is reversed, and the fatty acids 

 which are thus set free combine with the excess of alkali to form soaps. 

 The process of the hydrolysis of fats by alkali is therefore known as 

 Saponification. 



Monoglycerides, i. e., glycerides containing only one fatty acid 

 molecule, and Diglycerides are readily procurable in the laboratory, 

 but they do not usually occur in natural fats unless they have been 

 exposed to the action of fat-splitting enzymes (Lipases) or other saponi- 

 fying agencies. In the Triglycerides the fatty-acid radicals need not 

 all be identical and two or even three different fatty acids may be 

 combined with one and the same molecule of glycerol to form neutral 

 fat. 



The specific gravity of the fats is less than that of water, arid when 

 liquid, or liquefied by heat, those which are insoluble in water float 

 upon the top of it. The fats which are formed from the higher fatty 

 acids are insoluble in water, while the solubility of the lower members 

 in water decreases as the number of carbon atoms in the fatty acid 

 molecule increases. They are soluble in a variety of organic solvents, 

 and form very stable suspensions or emulsions in water in the presence 

 of emulsifying (surface-tension reducing) agents such as soaps, bile- 

 salts, saponins and so forth. 



1 The separation of glycerol from fats was first accomplished by the Swedish chemist 

 Scheele, in 1779. News of this discovery had, however, not yet reached the legislative 

 assembly of one of the allied nations in 1914, with the result that in 1915 a responsible 

 official of the executive, in reply to the inquiry of a legislator stated that it had only 

 recently been discovered that nitroglycerin could be made from fats. It is perhaps 

 time that a civilization which is based on mechanics, physics and chemistry should insist 

 on a rudimentary knowledge of the practical import of these sciences on the part of its 

 legislators and executives. 



