6 INTRODUCTION TO GENERAL SCIENCE 



What happens? Why? Does it happen immediately? 

 Why? 



d. Remove top cork, remove candle, light, it and return it 

 to the chimney, pushing in bottom cork, halfway, as at first. 

 Place bottom of chimney in a saucer nearly filled with water, 

 and immediately insert top cork. 

 ' What happens? Why? 



We conclude that combustion is concerned with two things, 

 the material to be burnt, called the combustible, and something 

 which aids the combustion, called the supporter of combustion. 



Returning now to the matter of combustion in general, we 

 can state that it is the chemical union of at least two materials, 

 the combustible and the supporter of combustion. Where 

 this union is rapid, we have the ordinary combustion. When 

 the combustible and supporter of combustion are thoroughly 

 mixed, we have the proper conditions for an explosion. Yet 

 the union is not always rapid; it may be very slow. Thj 

 rusting of iron and the decay of wood are examples of slow 

 combustion. The most common supporter of combustion is 

 oxygen, which comprises about one fifth of the atmosphere. 

 Whenever combustion takes place, whether it is ordinary or 

 slow, heat is produced. In the case of many examples of slow 

 combustion the heat escapes and cannot be perceived. Some- 

 times the heat does not escape, but accumulates gradually 

 until the material is hot enough to produce ordinary combus- 

 tion without the application of exterior heat. We call this 

 spontaneous combustion. 



Experiment 2. Spontaneous Combustion. 

 Apparatus : Ring stand, or wire ring four inches in diam- 

 eter, supported, test tubes, tweezers. 



Materials : Phosphorus cut under water into pieces half the 



