254 



Domestic Science 



EXPERIMENT 111. To a watch-glassful of potassium 

 chlorate add about one-fifth its bulk of manganese 

 dioxide. Mix the two substances well together and 

 transfer the mixture to a test-tube. Fit the test-tube 

 with a well-fitting cork, through which passes a doubly- 

 bent delivery tube. Complete the fitting up of the 

 apparatus as shown in Fig. 81. Heat the tube gently 

 by making the Bunsen flame of such a height that the 

 tip just touches the under surface of the test-tube. 

 Start the heating at the end of the mixture nearer the 



Fig. 81. 



mouth of the test-tube and, when all the oxygen has 

 come off from this portion, gradually transfer the flame 

 toward the sealed end of the test-tube. Oxygen will 

 be quickly given off and several jars may be obtained 

 from the quantity of mixture suggested for use. 



173. On consideration of the temperature required 

 to procure oxygen from this mixture, it will probably 

 be noticed that it is given off much more readily from 

 the mixture than from either of the two substances 

 separately. Careful investigation of the action which 



