PRELIMINARY EXPERIMENTS Xlii 



some hours, examine the saucers and bottles and compare 

 and record the results. Explain. State three conditions 

 that are favorable to evaporation. State three ways in 

 which evaporation may be prevented or decreased. 



Tests for Acid, Alkaline, and Neutral Substances. For 

 acid tests, use sour buttermilk (which contains lactic acid), 

 or hydrochloric acid diluted in ten parts water, or strong 

 vinegar (which contains acetic acid). Has the acid a char- 

 acteristic (" sour ") odor and taste (test it only when very 

 dilute)? Rub dilute acid between the fingers; how does 

 it feel ? Is there any effect on the fingers ? Obtain litmus 

 paper at a druggist's. Dip a strip of red litmus and of 

 blue litmus paper into the acid. What result ? 



For alkaline tests, dissolve in a glass of water a spoonful 

 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 



