COMPOSITION OF LIFELESS AND LIVING THINGS 11 



13. Nitrogen (symbol, N) and the composition of the air. 

 Laboratory Study No. 5: Demonstration. 



Fasten a candle to a piece of cardboard and float the latter on a 

 tray of lime water. Light the candle, and cover the flame with 

 an inverted wide-mouthed bottle, bringing the latter slowly down 

 until the edge rests on the bottom of the tray. Allow the candle 

 to burn as long as it will. Then turn the bottle right side up, cover- 

 ing the mouth with the cardboard, keeping inside the bottle the lime 

 water that has risen to take the place of the oxygen. Shake the 

 contents of the bottle, to make the lime water absorb the carbon 

 dioxid, and allow it to stand till the upper part of the jar is clear. 

 Keep the bottle covered to prevent the mixing of air with the 

 nitrogen. 



1. Examine a bottle of nitrogen. Is it a solid, a liquid, or a 



gas ? What is its color ? 



2. Thrust a burning splinter of wood into the nitrogen. 



a. Tell what was done. Does the wood continue to 



burn? 



b. Does the nitrogen burn? 



c. In what respect does nitrogen differ from oxygen? 



3. State four characteristics of nitrogen. 



4. Why does carbon burn faster in oxygen than in air? 



5. Air consists principally of oxygen and nitrogen. The 



water in the bottle represents the amount of oxygen 

 there was in the bottle of air, and the nitrogen 

 occupies the rest of the space. 



a. About what fractional part of the air in the bottle was 

 oxygen ? 



6. What fractional part of the air in the bottle is nitro- 

 gen ? 



6. Expose to the air of the room for a half hour or more a 



dish with some clear lime water, 

 a. Describe the experiment, stating the effect on the lime 



water. 

 6. What substance does this experiment prove to be 



present in air? 



