CARBON AND SOME OF ITS COMPOUNDS 



165 



of which is covered with lime-water to the depth of about an inch. When 

 the stick ceases to burn, withdraw it and shake the lime-water. 



iii. Carbon dioxide produced by breathing. (a) Blow through a piece 

 of glass tube into some clear, freshly made lime-water contained in a beaker. 



FlQ. 110. Burning a candle in air in a FIG. 111. The air breathed out from 

 glass jar. the lungs contains carbon dioxide, and 



will turn clear lime-water milky. 



Milkiness is at first produced, but if the blowing is continued long enough 

 it disappears. 



Fill a jar with water and invert it in a basin of water. Blow air from 

 your lungs into the jar by means of a tube. When the jar is full of air 

 place a glass plate under it and lift it out of the water. Show that the 

 air will extinguish a lighted taper. 



(6) Repeat the two preceding experiments by blowing air from a bellows 

 instead of from the lungs. Notice that this unbreathed air has not the 

 same effects upon a lighted taper or lime-water as breathed air. 



iv. The air contains carbon dioxide. Pour some clear lime-water into 

 a watch-glass, or some other shallow 

 vessel. Leave it exposed to the 

 atmosphere for a little while. Notice 

 the thin white scum formed on the 

 top. The carbon dioxide in the air 

 has turned the top layer of liquid 

 milky. 



v. Breathing changes the character 

 of air. Fit two bottles with corks 

 and tubes as shown in Fig. 112. See 

 that the corks are air-tight. Put 

 some clear lime-water into each bottle. 

 Place the tube C, or an india-rubber 

 tube leading from it, in your mouth. 

 When you suck at the tube, air is blown by c through B f / ora the i un gs 

 drawn in through the glass tube which the lime-water in B is turned milky. 



