SOAP AND SOAP MAKING 69 



Save a few drops of it. Into the greater portion put a small 

 piece of litmus paper (either color; why?); then add dilute 

 hydrochloric acid drop by drop, stirring the solution after every 

 drop, until the litmus is just barely pink (lavender). If you 

 get too much acid, add a drop more of sodium hydroxide solu- 

 tion. The base and the acid are said to neutralize each other. 

 6. Remove the litmus, and evaporate the solution over a 

 flame until crystals begin to appear. Then let the solution 

 evaporate further by itself. What is the shape of the crystals? 

 Taste the crystals and the solution. What substance is formed 

 by the neutralization of sodium hydroxide by hydrochloric 

 acid? 



c. Take about 5 cu. cm. of filtered lemon juice, add a small 

 piece of litmus paper, and neutralize the solution with lime- 

 water. Remove the litmus, and boil the solution vigorously. 

 You should get a white precipitate of calcium citrate. Give 

 your results. 



d. On a piece of black or blue woolen cloth put a drop of 

 concentrated hydrochloric acid, and let it remain for a few 

 minutes. What happens? Now treat the acid spot with dilute 

 ammonia water. What is the result? How could you remove 

 an acid spot from cloth? 



Make another spot on the cloth; then apply a thin paste of 

 baking soda (sodium bicarbonate). Will this do as well as 

 ammonia water? 



EXERCISE 67 

 SOAP AND SOAP MAKING 



Apparatus and Materials. Olive oil, sodium hydroxide solution, 

 solid sodium hydroxide, "tin" can, lard, salt, blotting paper or news- 

 paper, red litmus paper, 'linseed oil, limewater, test tubes. 



a. In a test tube put about 2 cu. cm. of sodium hydroxide 

 solution and 1 or 2 drops of olive oil. Close the test tube with 



