THE SCIENCE OF THE KITCHEN 115 



strip of red litmus paper. What change takes place? This 

 is a test for a base. 



; 3. Dissolve some salt in water. Put in this a piece of red 

 and also one of blue litmus paper. Does any change occur? 

 This is said to be a neutral substance. 



4. Get as many common substances as you can from the 

 kitchen, such as lemon, orange, limewater, sugar, sour milk, 

 sweet milk, buttermilk, baking soda, cream of tartar, baking 

 powder, tomatoes, an apple, any fresh fruit, tea, coffee, wash- 

 ing soda, soap, gold dust, wood ashes, drinking water. 



Test each one of these with both red and blue litmus paper. 

 Test the juices of the fruits. Dissolve the powders in water. 

 After letting the ashes stand, pour through a filter paper. 

 Steep the tea and coffee in hot water. Place the name of each 

 substance under one of the following headings in your notebook. 



ACID BASE NEUTRAL 



Soaps. Soaps are made by the action of fats on alkalies. 

 One called caustic soda makes hard soaps ; another called 

 caustic potash makes soft soaps. The cleansing action of 

 soaps is due to the fact that they unite with the fatty sub- 

 stances that hold the dirt, thus freeing it, and allow it to be 

 washed away. Washing soda also acts on grease, and most 

 washing powders are mixtures of this soda and powdered 

 soap. 



Hard water. Some hard waters contain chemicals in 

 solution which interfere with the action of the soap, since 

 the soap acts on these chemicals before uniting with the 

 grease around the dirt. Sometimes this hardness can be 

 overcome by boiling, as when the chemical is calcium bi- 

 carbonate. This is called temporary hardness. Another 

 kind, not so easily remedied, is called permanent hardness. 

 Enough soap must be used to counteract all the chemical 

 before the soap will have any cleansing power ; and the sub- 



