136 THE WATERS OF THE EARTH 



and hydrogen will be freed. Allow the gas to escape for several 

 minutes, so as to rid the generating bottle of the air in it. Collect 

 several bottles full of the hydrogen. Keep the bottles inverted. 

 Examine the hydrogen in one of the bottles. Has it color or odor ? 

 Holding the mouth downward thrust a lighted splinter into an- 

 other bottle. The splinter does not continue to burn in this gas 

 but the gas itself burns. Place another bottle mouth up on the 

 table and allow it to stand for several minutes. Insert a lighted 

 splinter. Why is not the hydrogen still present ? 



Draw out a glass tube so that the bore will be about as large as 

 the point of a pencil and insert it in the rubber delivery tube. Pour 

 more acid into the bottle and after this has been working for several 

 minutes touch a lighted match to the glass tip of the rubber delivery 

 tube. A jet of burning hydrogen will be formed. Hold a cold, dry 

 beaker over this burning jet. Water drops will collect in the beaker. 

 The hydrogen is combining with the oxygen of the air and water is 

 being formed. 



Pure water is a colorless, odorless, tasteless liquid. In 

 Experiment 15 we decomposed water by the electric current 

 and found it to be composed of two gases, hydrogen and 

 oxygen. In Experiment 56 we burned hydrogen, thus 

 uniting it chemically with the oxygen of the air and forming 

 water. Oxygen we have studied. Hydrogen is a colorless, 

 odorless, transparent gas, the lightest of all known sub- 

 stances. It must be handled carefully, because if it is mixed 

 with oxygen and the mixture is ignited, a violent explosion 

 results. 



Effects of Varying Temperatures on Water. We have 

 learned that water evaporates at any temperature and in so 

 doing always absorbs heat from its surroundings. When it 

 condenses it gives out the heat absorbed during evaporation. 

 When water at ordinary temperatures is heated it expands 

 until it reaches the boiling point. At this temperature, 

 the change of water from liquid to vapor goes on most 



