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PHYSIOLOGICAL CHEMISTRY 



(c) Repeat (b) using rancid olive oil. What sort of an emulsion do you get 

 and why? It is impossible to emulsify a highly rancid fat due to the excessive 

 formation of rather insoluble soaps about the oil drops. 



(d) Shake a drop of neutral olive oil with 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-ether mixture to evaporate 

 spontaneously. Examine the crystals under the microscope and compare them 

 with those reproduced in Figs. 56, 57, and 58, on pages 179, 182 and 184. 



7. Saponification of Bayberry Tallow. 1 Fill a large casserole two-thirds 

 full of water rendered strongly alkaline with solid potassium hydroxide (a stick 

 one inch in length). Add about 10 grams of bayberry tallow and boil, keeping 

 the volume constant by adding water as needed. When saponification is com- 



FIG. 58. PORK FAT. 



plete 2 remove 25 c.c. of the soap solution for use in Experiment 8 and add concen- 

 trated hydrochloric acid slowly to the remainder until no further precipitate is 

 produced. 3 Cool the solution and the precipitate of free fatty acid will rise to the 

 surface and form a cake. In this instance the fatty acid is principally palmitic 

 acid. Remove the cake, break it into small pieces, wash it with water by decan- 

 tation and transfer to a small beaker by means of 95 per cent alcohol. Heat on a 

 water-bath until the palmitic acid is dissolved, then filter through a dry filter 

 paper and allow the filtrate to cool slowly in order to obtain satisfactory crystals. 

 Write the reactions which have taken place hi this experiment. 



When the palmitic acid has completely crystallized filter off the alcohol, dry 

 the crystals between filter papers and try the tests given hi Experiment 10, p. 185. 



8. Salting-out Experiments. To 25 c.c. of soap solution, prepared as de- 

 scribed above, add solid sodium chloride to the point of saturation, with continual 

 stirring. A menstruum is thus formed in which the soap is insoluble. This 



1 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." 



2 Place 2 or 3 drops in a test-tube full of water. If saponification is complete the prod- 

 ucts will remain in solution and no oil will separate. 



a Under some conditions a purer product is obtained if the soap solution is cooled before 

 precipitating the fatty acid. 



