26 



An Account of the Soil 



[PT. I 



on to the calcium carbonate and see how the carbon 

 dioxide is given off. After effervescence ceases blow air 

 gently through the tube A to displace the carbon dioxide 

 and then weigh again. The loss of weight represents the 

 carbon dioxide. 



Next treat some soil with sulphuric acid. If there is 

 vigorous effervescence you can proceed to study the gas 

 evolved. Put some soil into a 250 c.c. flask fitted with 



Fig. 9. Apparatus for determining 

 carbon dioxide in chalk. 



Fig. 10. Collection of carbon di- 

 oxide from a soil rich in chalk. 



a thistle funnel and delivery tube : pour sulphuric acid 

 1 part of acid to 1 of water on to the soil and collect 

 the gas over the water (Fig. 10). Put a lighted taper to 

 the jar: the gas will neither burn nor will it allow the 

 taper to burn. Pour in some clear lime water: a dense 

 milkiness is produced. Collect another jar of the gas and 

 stand it over caustic soda. The gas is rapidly absorbed 

 and the soda rises in the jar. A third jar can be used to 

 demonstrate the heaviness of the gas as compared with 

 air: pour the gas into an empty jar containing some clear 

 lime water: a milkiness is produced. Now all these 



