134 Introduction to the Study of Science 



ated and by conducting it through a rubber tube, the end of which 

 should reach the bottom of the collecting bottle, enough may be 

 secured. Fill several bottles and cover each promptly with glass or 

 wet filter paper until ready for use. 



Exercise : Properties of carbon dioxid. To determine when a 

 bottle is full, have a candle fastened to a wire so that it will reach the 

 bottom of the bottle. Light it and let down slowly. When it meets 

 the gas, it will be extinguished. Relight and try again and when 

 extinguished, observe the level at which this occurred. Repeat until 

 you have the bottle full. 



Experiment with the gas in these ways : 



(1) If you are not certain of its influence upon combustion, intro- 

 duce a burning candle into a bottle of the gas. For comparison put 

 a burning candle into a similar bottle of air. Does the gas generated 

 from the marble support combustion? 



(2) Put some limewater into a bottle, close, and shake vigorously. 

 What does the reaction of the limewater indicate as to the content of 

 the bottle? 



(3) Turn a bottle upside down and insert a burning candle ; when 

 extinguished, remove, light, and again introduce it. Repeat several 

 times. The behavior of the flame and of the glowing wick of the 

 candle at successive introductions is interesting. Toward the end 

 of the trials is the fire completely extinguished? If not, explain 

 why it is not. Would the gas remain in the bottle, if it were lighter 

 than air? Compare with this the fact that you collect it in open 

 bottles. Can you guess approximately the difference between the 

 weights of the gas and of air? 



(4) Fill a bottle containing gas one third to one half full of water. 

 Cover with the palm of one hand and -shake thoroughly. Note the 

 sensations on the surface of the hand. What do they suggest as to 

 the behavior of the contents of the bottle? Submerge the mouth of 

 the bottle in water and open. What happens? What does this show 

 as to the amount of gas absorbed by the water ? Is the gas soluble in 

 water ? 



(5) Mix a small amount of clean water with the gas in one bottle 

 by shaking vigorously. Taste the mixture. Recall the taste of 

 " soda water." In what respects are the two tastes similar? 



Exercise. Prepare a summary of the points observed as to the 

 behavior and nature of carbon dioxid. 



1. What is its influence upon combustion? What facts support 

 your conclusion? What use is made of it in fire extinguishers? 



2. Is carbon dioxid soluble in water? What effect does it have on 



