41-42] CARBON DIOXIDE AND AMMONIA 



17 



41. Carbon dioxide gas resembles nitrogen in that it 

 will extinguish a flame as shown in the last experiment, but 

 it differs from it in several ways. To show that it is much 

 heavier than air pour the gas from one jar into another, 

 as shown in figure 19. As the gas is invisible, nothing will 

 be seen to pass. Now plunge a lighted taper into each of 

 the jars. In the one which originally contained the gas, 

 the taper will continue burning, showing that no carbon 

 dioxide remains, whilst in the other jar the taper will be 

 extinguished, showing that the heavy gas has been poured 

 from the first jar into the second. 



42. Another property by which carbon dioxide may be 

 recognised is its action on lime-water. Half fill a small 



beaker with lime-water 

 and place it so that the 

 delivery-tube of the ap- 

 paratus (fig. 18) dips into 

 the liquid. Allow the gas 

 to pass through the lime- 

 water for a few minutes. 



I 



Fig. 18 



Fig. 19 



First the liquid becomes milky, because the lime has 

 combined with the carbon dioxide to form carbonate of 

 lime or chalk, which is not soluble in water. In a short 

 time, however, the liquid becomes clear again : this is 

 because the chalk, although insoluble in pure water, is 

 soluble in water which contains carbon dioxide gas dissolved 

 in it. If the clear liquid is boiled for a few minutes the 



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