10 LABORATORY WORK IN PHYSIOLOGICAL CHEMISTRY. 



allow them to float on the surface of water. They are solu- 

 ble in ether, chloroform, and benzol; hot alcohol also dis- 

 solves them, but upon cooling they separate out usually in 

 crystalline form. Under certain conditions fats undergo a 

 peculiar physical change called emulsification, which is beau- 

 tifully illustrated in the natural state of the fat in milk. 

 Under the influence of superheated steam, acids, or ferments, 

 fats are broken down into their component parts fatty 

 acids and glycerol. When an alkali or sodium alcoholate is 

 employed, soaps and glycerol are formed and the process 

 is called saponification. Another form of decomposition is 

 effected when fats remain for any length of time in contact 

 with the oxygen of the air. They then become rancid by 

 the liberation and subsequent oxidation of the fatty acid 

 from the molecule and the formation of lower volatile acids 

 which cause unpleasant odors and tastes. 



Try the following tests, making use of olive oil : 

 (a) Test its solubility in water; ether; chloroform; alco- 

 hol. 



(6) Test its reaction. What is the normal reaction of a 

 fat? Express by equations what occurs when butter becomes 

 rancid. 



(c) In a test-tube warm a few drops with potassium bisul- 

 phate. Notice odor. What is the reaction taking place? 



(d) Let a drop of an ether solution of a fat fall upon paper. 



(e) Dissolve a little lard in 10 c.c. of a mixture of equal 

 parts of alcohol and ether. Allow this to remain uncovered 

 until crystals begin to form. 



(/) Saponification (Bayberry Wax Tripalmitin). 



Place a piece of the wax, half the size of a walnut, in an 

 evaporating-dish which is half full of water. Then add about 



