46 BURNING OR OXIDATION 



burns quietly. Oxygen for this experiment can be produced 

 in the following way. 



36. How to Prepare Oxygen. Mix a small quantity of potas- 

 sium chlorate with an equal amount of manganese dioxide 

 and place the mixture in a strong test tube. Close the 

 mouth of the tube with a one-hole rubber stopper in which 

 is fitted a long, narrow tube, and clamp the test tube to an 

 iron support, as shown in Figure 22. Fill the trough with 



FIG. 22. Preparing oxygen from potassium chlorate and manganese dioxide. 



water until the shelf is just covered and allow the end of the 

 delivery tube to rest just beneath the hole in the shelf. 

 Fill a medium-sized bottle with water, cover it with a glass 

 plate, invert the bottle in the trough, and then remove the 

 glass plate. Heat the test tube very gently, and when gas 

 bubbles out of the tube, slip the bottle over the opening in 

 the shelf, so that the tube runs into the bottle. The gas will 

 force out the water and will finally fill the bottle. When all 

 the water has been forced out, slip the glass plate under the 

 mouth of the bottle and remove the bottle from the trough. 

 The gas in the bottle is oxygen. 



Everywhere in a large city or in a small village, smoke is 

 seen, indicating the presence of fire ; hence there must exist a 

 'large supply of oxygen to keep all the fires alive. The supply 



