DIGESTION AND ABSORPTION. 183 



process of saponification. A complete and typical 

 saponification requires a more careful apportion- 

 ment of the amount of oil and of alkali used and an 

 application of heat. 



() Repeat the experiment substituting a 25% solu- 

 tion of potassic hydrate. The result is similar. 



(c) What is the chemical formula of palmitin? Of 

 stearin? Of olein ? 



(d) What is the chemical formula of palmitic acid? Of 

 stearic acid ? Of oleic acid ? 



(e) Write generalized formulae for each of these acids. 



(3) Write the reaction which takes place in saponifica- 

 tion of palmitin; of olein. Note the ready solubil- 

 ity of the products of this reaction in water. 



(4) To a solution of soap add any aqueous solution of a 

 calcium salt soluble in water, e. g., calcium chloride 

 a curdy white precipitate separates out. Write the 

 formula of the reaction. 



May the reaction have any relation to hygiene or 

 therapeutics ? 



(5) The emulsification of oils. Gould defines an emulsion 

 as "water or other liquid in which oil in minute sub- 

 division of its particles is suspended." One may add, 

 more or less permanently suspended. For, if one shake 

 together vigorously 2 c. c. of oil with an equal amount 

 of water in a test tube he is able to bring about a 

 minute subdivision and temporary suspension of the 

 oil in the water. While the oil is in this temporary 

 physical condition it has the white color typical of 

 emulsions in general. In a few minutes, however, 

 the particles, as they rise to the top of the liquid 

 coalesce into minute globules; then into larger and 

 larger globules and finally into a homogeneous, super- 

 natant oil-layer. 



