CHAPTER VI 



THE WATERS OF THE EAETH 



Importance of Water. Water is found to some extent 

 everywhere on the earth's surface. It is necessary to the 

 life of all plants and animals and makes up a large part of 

 their weight. Man may live without food for a few weeks 

 but cannot live more than a few days without water. The 

 earth has been likened by some writers to a water engine, 

 since water has played such an important part in its history. 



Composition of Water. Experiment 56. (Teacher's Experi- 

 ment.) Place a small handful of zinc scraps in a strong wide- 

 mouthed bottle. Fit the 

 bottle with a two-holed rub- 

 ber stopper having a thistle 

 tube extending through one 

 hole and a bent delivery 

 tube through the other. 

 The thistle tube should 

 reach nearly to the bottom 

 of the bottle. Connect the 

 delivery tube with the shelf 

 of a pneumatic trough by a FIQUBE 71 



rubber tube. Have several 



inverted 8-oz., wide-mouthed bottles filled with water on the shelf 

 of the trough. (Figure 71.) Pour enough water through the 

 thistle tube to partly cover the zinc and then pour on commercial 

 hydrochloric acid or sulphuric acid diluted 1 to 10. 



Chemical action will take place between the zinc and the acid 



135 



