168 JUNIOR GRADE SCIENCE 



a gas is given off and collects in the jar. When a burning taper is extinguished 

 immediately it enters the jar, take out the delivery tube and put it into 

 another jar. Cover the first jar of gas with a glass plate. In the same way 

 collect several jars of the gas. 



FIG. 114. Apparatus for the FIG. 115. Carbon dioxide gas is 



preparation and collection of car- heavier than ah", and can therefore 



bon dioxide. be poured from B into A, like a 



liquid. 



ii. Properties of carbon dioxide. (or) Notice that the gas is (1) invisible 

 and without taste or smell ; (2) extinguishes a lighted taper ; (3) must be 

 heavier than air or it could not be collected in the waj' described. 



(6) Pour the gas from one jar (B) into another (A), as shown in the 

 diagram (Fig. 115), and test both jars by a lighted taper. It will be seen 

 that the lower jar contains the carbon dioxide. 



iii. Acid solution formed by carbon dioxide. Pour a little water made 

 blue with litmus into a jar of the gas and shake it up. Some of the gas 

 dissolves, and the colour of the solution turns red. Boil the solution ; 

 the carbon dioxide is driven off, and the blue colour is regained. 



iv. Action of carbon dioxide on lime-water. Pass the gas from the 

 delivery tube through some lime-water. Observe that a milkiness is pro- 

 duced, owing to the production of a white powder or precipitate, which 

 disappears after a short time. 



Boil the solution thus obtained, and notice that the milkiness again 

 appears. 



Filter the milky solution, and so obtain the white powder on a filter 

 paper. Add a few drops of dilute hydrochloric acid to the powder. Notice 

 the effervescence. Test the gas which is given off ; it puts out a flame. 



v. Burning of magnesium in carbon dioxide. Hold a piece of magnesium 

 ribbon in a crucible tongs, ignite and place in a jar of the gas (take care not 

 to allow the burning metal to touch the sides of the jar). It burns with a 

 crackling noise, and black specks appear on the sides of the jar. A white 

 powder, which may be identified as magnesium oxide, is also formed. In 

 order to dissolve the oxide add a little dilute hydrochloric acid to the jar, 

 and shake up. The contents of jars from the class should be collected in 

 one, filtered, and the black powder remaining on the paper washed with 



