PRELIMINARY EXPERIMENTS xiii 



of baking soda or some laundry soap ; or dissolve an inch 

 stick of caustic soda in a glass of water. Test odor and 

 " feel " of last solution as with the acid ; likewise test effect 

 of alkaline solution on red and blue litmus paper. Record 

 results. Alkalies are strong examples of a more general 

 class of substances called bases, which have the opposite 

 effect from acids. 



Test pure water. Has it odor ? A taste ? Test it with 

 red and blue litmus paper. Water is a neutral substance ; 

 that is, it is neither an acid nor an alkali (or base). 



After making appropriate tests, write ac, al, or neu after 

 each name in the following list (or write in three columns): 

 vinegar, soda, saliva, sugar, juice of apple, lemon, and 

 other fruits, milk, baking powder, buttermilk, ammonia, 

 salt water. 



Pour some of the alkaline solution into a dish, gradually 

 add dilute acid (or sour buttermilk), stirring with glass rod 

 and testing with litmus until the mixture does not turn red 

 litmus blue nor blue litmus red. The acid and alkali are 

 then said to have neutralized each other, and the resulting 

 substance is called a salt. The salt may be obtained by 

 evaporating the water of the solution. Most common 

 minerals are salts. If the last experiment is tried with 

 soda and sour buttermilk, the demonstration will show 

 some of the facts involved in bread making with the use 

 of these substances. 



Tests for Starch. - - Starch turns blue with iodine. The 

 color may be driven away by heat, but will return again as 

 the temperature lowers. Produce a few cents' worth of tinc- 

 ture of iodine and dilute it. Get a half dozen pieces of 

 paper and cardboard, all different, and test each for starch 

 by placing it over mouth of bottle and tipping the bottle 

 up. It much starch is present, the spot will be blue-black 



