FATS AND PHOSPHATIDES 265 



above, shaking after each addition until after a vigorous shaking 

 the pink color in the alcohol layer just remains. Allow the two 

 layers to separate in a large test tube. Draw off by means of a 

 pipette the layer of neutral oil, wash it by shaking gently with 

 one or two portions of distilled water in a test tube, and save it 

 for use in the experiments following where neutral oil is called 

 for. 



Emulsification. The property of forming an emulsion is of 

 great importance. The fat is held in suspension in the liquid 

 in the form of minute droplets. Study the conditions affecting 

 emulsification as follows: 



5. Shake together thoroughly about 1 c.c. of neutral oil and 

 a few c.c. of water. The oil and water quickly separate into two 

 layers. 



6. Repeat 5,. first adding a small amount of sodium car- 

 bonate solution to the tube. The milky appearance of the water 

 layer indicates that a portion of the oil has emulsified, but the 

 action is not extensive. To neutral oil and water add soap solu- 

 tion and shake. A good emulsion forms, indicating the favorable 

 action of soap on emulsion formation. Upon this property of 

 soap depends in large measure its usefulness in cleansing. Greasy 

 material on the surface washed is emulsified, and the insoluble 

 "dirt" thus liberated and carried away by the water and the 

 "suds." 



If rancid oil (oil which contains free fatty acid), water and an 

 alkali, e.g. Na.,C0 3 are shaken together a good emulsion is formed, 

 since the mixture contains the soap produced by the action of the 

 fatty acids and the alkali. 



Lymph has the power of aiding in the formation of an emul- 

 sion. This may be demonstrated (Ranvier's experiment) by 

 bringing drops of oil and lymph together under the microscope. 

 Intense activity will be observed at the juncture of the liquids, 

 and the oil passes into an emulsified state. 



7. Examine an emulsion under the microscope. Observe the 

 tiny globules of fat. Examine a drop of milk under the micro- 

 scope. The fat in milk is emulsified. On standing, a portion of 



