48 THE FOOD OF PLANTS CHAP. 



The Action of Vitiated Air on Lime-Water 

 Experiment 29 



We have noticed that a candle or match will not 

 burn in vitiated air. It has another property which 

 will be useful in identifying it when we come 

 across it. 



If we shake up some lime with water and then 

 filter, we obtain a clear solution of lime in water. 



Pour a little of this clear lime-water into a wide- 

 mouthed bottle, and lower a lighted candle into the 

 bottle and then cover up the mouth. The candle 

 soon goes out. 



Remove the candle, replace the stopper in the 

 bottle, and shake up the lime-water with the vitiated 

 air. A white powder is formed, the lime-water 

 becoming milky in appearance. 



Now take a fresh supply of lime-water in another 

 bottle, and blow through it. This also becomes 

 milky in appearance, owing to the vitiated air from 

 the lungs. 



We have here then a simple means of testing for 

 the presence of vitiated air. 



Vitiated Air is produced by burning Charcoal 



We have seen that various different bodies in 

 burning produce vitiated air : let us now see whether 

 burning charcoal also does so. 



