136 



PHYSIOLOGICAL CHEMISTRY. 



5. Emulsification. (a) Shake up a drop of neutral 1 olive oil 

 with a little water in a test-tube. The fat becomes finely divided, 

 forming an emulsion. This is not a permanent emulsion since the 

 fat separates and rises to the top upon standing. 



(b) To 5 c.c. of water in a test-tube add 2 or 3 drops of 0.5 

 per cent Na 2 CO 3 . Introduce into this faintly alkaline solution a 

 drop of neutral olive oil and shake. The emulsion while not per- 

 manent is not so transitory as in the case of water free from 

 sodium carbonate. 



(c) Repeat (b) using rancid olive oil. What sort of an emul- 

 sion do you get and why? 



(d) Shake a drop of neutral olive oil with a dilute albumin 

 solution. What is the nature of this emulsion? Examine it under 

 the microscope. 



6. Fat Crystals. Dissolve a small piece of lard in ether in a 

 test-tube, add an equal volume of alcohol and allow the alcohol- 



FIG. 37. 



PORK FAT. 



ether mixture to evaporate spontaneously. Examine the crystals 

 under the microscope and compare them with those reproduced in 

 Fi g s - 35, 36 and 37, on pages 131, 134 and 136. 



7. Saponification of Bayberry Tallow. 2 Fill a large casserole 



1 Neutral olive oil may be prepared by shaking ordinary olive oil with a 10 

 per cent solution of sodium carbonate. This mixture should then be extracted 

 with ether and the ether removed by evaporation. The residue is neutral 

 olive oil. 



2 Bayberry tallow is derived from the fatty covering of the berries of the wax 

 myrtle. It is therefore frequently called " myrtle wax " or " bayberry wax." 



