82 



THE PRODUCITON AND USE OF HEAT 



seeing that all of the air is expelled from the bottle by the water; then, 

 keeping the mouth of the bottle beneath the surface of the water, 

 invert the bottle and place it over the end of the delivery tube. As 

 the oxygen escapes from the delivery tube, it bubbles into the bottle 

 of water and crowds the water out. When the first bottle is full, place 

 another bottle over the end of the delivery tube just as the first one 

 was placed. Set the full bottles on the top of the table, keeping them 

 inverted. The water around the mouth of the bottle will keep the 

 oxygen from getting out. When you have driven as much oxygen 



FIG. 6!. The preparation of oxygen. Potassium chlorate and manganese 

 dioxide are placed in the test-tube and heated and the oxygen is collected in 

 bottles. Be careful to see that the delivery tube extends entirely through 

 the rubber stopper. Do not allow the delivery tube to become clogged. 



as possible from the mixture in the tube, remove the end of the deliv- 

 ery tube from the water; then remove the flame from the test tube. 



Study the oxygen obtained as follows: 



(a) Effect of Pure Oxygen on a Burning Splinter. Place a splinter 

 of wood in a bottle of oxygen to see that the wood does not burn in 

 oxygen at ordinary temperatures. Now heat the splinter, that is, 

 "set it on fire," and thrust it into a bottle of oxygen. What is the 

 result? In which, gas, oxygen or air, does the wood burn more 

 rapidly? Why? Ignite another splinter and blow out the flame 

 leaving the splinter merely glowing. Hold it in the air for a moment 

 to see whether it will again burst into a flame. If it does not, place 

 the glowing splinter in a fresh bottle of oxygen and observe the 

 result. How do you explain it? 



(6) Effect of Pure Oxygen on Smoldering Substances. Repeat the 



