27 



tube B, and clamp the test tube to an iron support as shown 

 in the figure. 



Fill the pneumatic trough with water until the shelf is 

 just covered, and allow the end of the delivery tube to rest 

 just beneath the hole in the shelf. Then fill a medium- 

 sized bottle with water and cover it with a glass plate or 

 heavy paper. Heat the test tube very gently, and when gas 

 bubbles rise rapidly through the water, place the inverted 

 bottle over the hole in the shelf and remove the plate. The 

 gas which issues from B will rise in the bottle and force out 

 the water. When all the water in the bottle has been dis- 



FlG. 20. Making oxygen. 



placed, slip the glass plate under the mouth of the bottle 

 and remove the bottle from the trough. The gas which has 

 been collected in the bottle is called Oxygen. 



Dip a splinter of wood smoldering at one end into the bot- 

 tle of oxygen. What happens ? Remove the stick, and re- 

 peat several times. How does the glowing stick change in 

 appearance ? 



Hold a piece of charcoal in a flame long enough to make 

 it glow faintly. Then place it in a bottle of oxygen. How 

 does it change in appearance ? 



