210 THE SKIN 



a) Test each solution with red litmus paper to determine 

 whether neutral or alkaline. 



b) To determine amount of alkali in each soap, pour table- 

 spoonful of vinegar into glass of water, add slowly to soap 

 solution and gently shake, noting amount required to change 

 soap solution from alkaline to acid. A piece of litmus paper 

 should be floating in each test tube and its change of color 

 carefully watched. 



