150 PLANT PHYSIOLOGY 



The alcohol found in fats is the trihydric alcohol called glyc- 

 erol, which is obtained on the market as glycerin. Its formula is 



CH2OH 



CHOH 



I 

 CH2OH 



Glycerol is a very heavy, colorless, viscid, sweetish liquid, which 

 is freely miscible with water in all proportions. It is used ex- 

 tensively in the manufacture of explosives such as dynamite and 

 nitroglycerin, and is obtained from fats by a process known as 

 saponification, which consists in treating the fat with an alkali. 

 As a result the glycerol is separated out, and the alkali unites 

 with the fatty acid forming a soap. Whether or not the soap formed 

 can be used as such, the process is called saponification and the 

 salt of the alkali and acid is a chemical soap. 



Fatty Acids. — Among the common fatty acids found in various 

 fats are formic (H.COOH), which is found in nettles and also in 

 the bodies of ants and bees; acetic (CH3.COOH), which occurs 

 in vinegar; butyric (C3H7.COOH), which is the common acid 

 of butter fat and occurs free in rancid butter, when the fat has 

 been broken down into its component parts; palmitic (C15H31. 

 COOH), which is common in palm oil and many fats; and 

 stearic acid (C17H35.COOH), which is present in most fats 

 and oils. 



It will be observed that the constitution of the above fatty 

 acids can all be expressed by the general formula CnH 2n +i.COOH. 

 In all the fats found in nature none have been obtained where n 

 was other than an odd number which makes the total number of 

 carbon atoms in the molecule even. Further, if we examine the 

 structure of one of the above acids, e. g., acetic acid 



H 



I 

 H— C— C— 



I I 

 H OH 



it is observed that v the carbon atoms are all saturated, by which is 

 meant that each of the four valencies of the carbon atoms are 

 completely " satisfied." The difference between "satisfied" and 



