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Introduction to the Study of Science 



Air indispensable to burning. At this point the question 

 may be raised whether the air is indispensable to burning. 

 The experiment just performed seems to show that it or a part 

 of it combines with the burning candle. The old experiment 

 of Lavoisier with burning lead in a closely covered dish pointed 



FIG. 19. Caustic soda in the lamp chimney absorbs the products of com- 

 bustion. The burning candle produces substances which are shown by this 

 experiment to weigh more than the amount of candle consumed. 



to this conclusion. But it may require a clearer demonstration 

 before the answer can be given positively. Is air indispensable 

 to burning ? You may find out the important point in this way. 



Exercise : Relation of air to combustion. Hold a lamp chimney 

 over a burning candle, so as to allow about one half an inch space at the 

 bottom for air to pass through. Gradually decrease the space and 

 observe the effects on the flame. Finally shut off the draft entirely. 

 Does the candle continue to burn ? Cover the top of the- chimney 

 with a piece of cardboard. What happens? (Compare this with 

 the ways of controlling the draft in a range or stove.) What do the 

 facts observed indicate as to the influence of air on combustion? 

 Does the candle burn more brightly with a draft from below than it 

 does when in the open air? Why? Does the brightness of the flame 



