WATER 



111 



holding a wire with a piece of platinum extending into 

 the arm, and a free end projecting outward. To the 

 projecting wires attach the wires 

 leading from the source of the elec- 

 tricity and turn on the current. As 

 soon as the current passes, bubbles 

 of gas rise from the pieces of plati- 

 num to the upper parts of the tubes. 

 The gas in one tube collects just 

 twice as rapidly as in the other. If 

 the gas in each tube is tested, the 

 tube with the smaller quantity will 

 be found to contain oxygen, while 

 the other tube with twice as much 

 volume will be found to contain 

 hydrogen. 



Thus the formula, water = H 2 0. 



Again, if oxygen and hydrogen 

 gases are mixed in a dry vessel and 

 then ignited, vapor collects on the 

 sides. This vapor, resulting from 

 the explosion or union of oxygen 

 and hydrogen, is the oxide of hydro- 

 gen, or water. 



Properties and uses. Pure water is an odorless and 

 tasteless liquid. In thin layers it appears colorless, 

 though in larger bulk it has a bluish tinge. At ordinary 

 pressure it boils at 100 C. (212F.) and freezes at 

 0C. (32F.) Most substances contract upon cooling. 



i 



F i g. 42. D e- 

 composition of 

 water. An electric 

 current passed 

 through the water 

 in the tubes decom- 

 poses it into hydro- 

 gen and oxygen. 



