ELEMENTS ATOMIC WEIGHTS MOLECULES, ETC. 9 



is surely full of gas, which is escaping at A. The gas at A 

 is now ignited and the gas cock turned down till a small 

 inverted flame is produced at A. The finger is now removed 

 from C and the flame at A will be seen to ascend the tube 

 and to burn at B. The gas issuing at C is immediately 

 ignited. If we consider these two flames, we shall see 

 that the one at C is composed of illuminating gas burning 

 in an atmosphere of air, and naturally the oxygen of the 

 air would be considered the supporter of combustion, 

 while the gas would be considered the combustible. The 

 flame at B is composed of air coming up the tube from A 

 which is burning in an atmosphere of illuminating gas, 

 and in this case we should naturally consider the illuminating 

 gas as the supporter of the combustion while the oxygen 

 of the air is the combustible. 



10. Kindling Temperature. While oxidation may take 

 place at any temperature, in order to start and to con- 

 tinue combustion, it is necessary for the combustible and 

 the supporter of combustion to be at a certain tempera- 

 ture, known as the kindling temperature. Each substance, 

 under the same conditions, has its own definite kindling 

 temperature. Phosphorus has a very low kindling tem- 

 perature, taking fire spontaneously in the air. This is due 

 to the fact that oxidation raises the temperature of the 

 phosphorus to its kindling point. If a bit of phosphorus 

 as large as a wheat grain is dissolved in a small amount 

 of carbon disulphide and the solution poured upon a filter 

 paper placed in an iron ring, as soon as the carbon disulphide 

 evaporates, the phosphorus will burst into flame. In this 

 case the finely divided condition of the phosphorus exposes a 

 relatively large surface to oxidation. When a candle flame 

 is extinguished by blowing upon it, the blast of air cools 

 the flame below its kindling point. 



The quantity of heat produced by combustion will de- 

 pend upon the quantity and the character of the gases 

 entering into reaction, while the degree of heat will depend 



