THE FATS. 11 



10 c.c. NaOH and boil until the substance is dissolved, adding 

 water from time to time as the solution evaporates, so that 

 the original volume is constantly maintained. Write the 

 reaction which is taking place. After complete solution, add 

 carefully dilute H,S0 4 until the reaction just becomes acid and 

 then cool. A greenish crust of free fatty acid will form on 

 the surface of the liquid, so that the solution may be poured 

 off. (Keep this solution.) Break the fatty acid crust into 

 small pieces and wash with tap water; finally dry between 

 filter-paper. Dissolve part of the fatty acid in 50 c.c. of hot 

 95 per cent alcohol, filter hot through a dry funnel and allow 

 the filtrate to cool slowly. 



Palmitic acid separates out in snowy-white crystalline 

 form. Examine some under the microscope and sketch the 

 crystals. 



(g) Saponification (Lard), 



Place about 100 c.c. of alcoholic potash in a flask contain- 

 ing 25 grams of lard. Warm the mixture upor. the water- 

 bath until a drop let fall into water is perfectly soluble. 

 Then pour the solution into an evaporating-dish containing 

 100 c.c. water and evaporate until the alcohol has been driven 

 off. While still hot acidify with dilute H 2 S0 4 and then 

 cool. Write the chemical equations for the various steps in 

 the procedure. The fatty acid rises to the surface and may 

 be easily removed from the liquid beneath. Unite this solu- 

 tion with the similar one in Experiment 1 and, after neutrali- 

 zation with Na 2 C0 3 , evaporate it down to about 5 c.c. What 

 substances are present in this solution? Retain this. 



