48 



LIVING IN AN OCEAN OF AIR 



I 



f 



Oxygen a Harmful and Useful Agent. There are 

 few useful things in this world which cannot at the same 



time be harmful or objection- 

 able. The air is no exception 

 to this general statement. 

 Man makes iron fences, iron 

 bridges, iron mosquito netting, 

 and sheet iron for cans, dishes, 

 covering for boats and roofs 

 of dwellings. Sooner or later 

 the oxygen of the air may 

 combine with the iron, making 

 a worthless mass of iron oxide, 

 without even strength enough 

 to hold itself up. 



What Substance in the Air 

 Aids Burning? If one were 

 to place three lighted candles 

 on the table and at the same 

 instant cover them with three 

 jars of different sizes, would 



the candles all burn for the same length of time? You 

 know what will happen : the candle in the largest jar 

 burns the longest. The largest jar has the most air, and 

 there is something in the air that helps things to burn. 



Demonstration 2. What Gas Helps Things to Burn? 



Fill two wide-mouth bottles, one with oxygen and the other 

 with nitrogen. 1 Place them mouth up, but cover with a small 

 glass plate. 



1. Plunge a flaming wooden splint into the nitrogen. Result? 

 Plunge a glowing coal on the end of the splint in the nitrogen. 

 Result? 



1 Prepare nitrogen by the following method : 



Put bundle of wet steel wool in wide-mouth bottle, put mouth down in 

 jar of water. Next day remove wool while under water. Close mouth of 

 bottle, remove from water, and set right side up. The gas in the bottle will 

 be practically all nitrogen. 



Wright Pierce 



Why are iron pipes sometimes 

 unreliable carriers of water ? 



