94 FIRST YEAR COURSE IN GENERAL SCIENCE 



cording to conditions of temperature and pressure. What 

 is commonly called " ammonia" is the gas ammonia dissolved 

 in water. Air dissolves in water and in this way the oxygen 

 necessary to life is furnished to fishes and other water ani- 

 mals. If a tumbler of drinking water is left standing for 

 a time, small bubbles may be seen clinging to the inside of 

 the glass. These bubbles contain air, and the water is not so 

 agreeable to drink as it was before the air left it. All natural 



FIG. 42. SOLUTION 

 OF AIR IN WATER 



FIG. 43. DIFFUSION OF 



GASES 



FIG. 42. The water here represented has been growing warmer while 

 standing for some hours. Air which was dissolved in the water has sepa- 

 rated and appears as bubbles on the glass. 1. What did the change of 

 temperature have to do with the change in the water? 2. How does air 

 become dissolved in water? 



FIG. 43. One of these flasks contains an invisible acid gas dissolved 

 in water; the other contains invisible ammonia gas, also in solution. If 

 these two gases come together, they form a new compound in the form of a 

 fine white solid. 1. What shows that they have diffused? 2. Suppose that 

 one of the bottles were removed; what change would occur? 



waters contain dissolved air, and much spring water contains 

 the gas carbon dioxide. If water is heated, the dissolved 

 air and other gases expand and escape. Such water tastes 

 stale or flat, even after it is cooled. 



102. Soda and Carbonated Waters. Large quantities 

 of carbon dioxide dissolved in water give the pungent, 

 slightly acid taste familiar in plain soda water. The name 

 "soda water" was given because the carbon dioxide was 



