26 



Our Surroundings 



Production of Water. When hydrogen unites with oxygen, 

 water is formed. To show how water is formed by the oxidation 

 of hydrogen, pass hydrogen from the generating flask through a 

 tube containing calcium chloride to absorb all moisture present. 

 After passing the hydrogen through this substance, allow it to 

 enter a glass tube ending in a narrow opening. Caution : Care 

 should be taken at this point to test the gas for purity, or freedom 

 from air, because hydrogen and air form a very explosive mix- 

 ture. This test may be safely made with a small amount of the 

 gas in a test tube around which a towel has been wrapped. 



PREPARING HYDROGEN 



Quickly bring the mouth of the tube to a Bunsen flame. If air 

 be present, a loud report will result. If no air is mixed with the 

 hydrogen, only a slight report will be heard, and a bluish flame will 

 be noted. When the hydrogen has been proved pure, hold a 

 glass plate in the escaping gas and notice if water is formed on it. 

 Then hold over the flame a thoroughly dry cold tumbler, and ob- 

 serve what occurs. 



Carbon. Carbon is a solid. It is the main element in or- 

 ganic matter, and an essential part of all living things. At ordi- 

 nary temperatures it is inactive and so will not unite readily with 



