FATS. 



137 



two-thirds full of water rendered strongly alkaline with solid potas- 

 sium 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 complete 1 remove 25 c.c. 

 of the soap solution for use in Experiment 8 and add concentrated 

 hydrochloric acid slowly to the remainder until no further precipi- 

 tate is produced. 2 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 decantation and transfer 



FIG. 38. 



PALMITIC ACID. 



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 in this experiment. 



When the palmitic acid has completely crystallized filter off the 

 alcohol, dry the crystals between filter papers and try the tests 

 given in Experiment 9, p. 138. 



8. Salting-out Experiment. To 25 c.c. of soap solution, pre- 

 pared as described above, add solid sodium chloride to the point 

 of saturation, with continual stirring. A menstruum is thus 



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

 the products will remain in solution and no oil will separate. 



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

 cooled before precipitating the fatty acid. 



