18 



CHEMISTRY, GEOLOGY 



Fi - 6 - is the best supporter of combus- 

 tion known. Thin iron wire will 

 burn readily in oxygen gas, throw- 

 ing off most brilliant sparks, called 

 scintillations. 



NITROGEN is also a gas. A 

 candle will not burn, nor can any 

 animal live, in it. It is sometimes 

 called azote^ which means against 

 life. It does not burn when 

 brought in contact with flame. It 

 is lighter than the atmosphere. 

 Although it destroys animal life, 

 the air we breathe contains four- 

 fifths of its bulk of nitrogen. ( See 

 Appendix, 5.) 



All the gases hitherto described 

 are colorless, and therefore invis- 

 ible. They are also elastic, which 

 means they can, by great press- 

 ure, be compressed into smaller 

 , bulk, but as soon as the pressure 



Questions. What is nitrogen ? Can animals live in it ? 

 What was its old name ? What did it mean ? Will nitrogen 

 burn ? How much nitrogen does the atmosphere contain ? 

 Why are the gases described invisible ? Are they elastic ? 

 What is the effect of pressure upon them ? 



