29. A good example of the effect of dissociation is shown by the temperature of the flame produced by the burning of hydrogen and oxygen. Theoretically, the temperature of the flame should be over 10,800°, while the temperature actually realized is but 4,500°, or a little less than one-half of the theoretical.
When a mixture of hydrogen and oxygen is exploded in a closed vessel, the theoretical temperature, when no dissociation occurs, is over 16,000°. The highest temperature yet obtained in experiments with these gases is less than 7,000°. Mixtures of hydrogen and air give much lower temperatures. Although dissociation cannot be held responsible for all of this difference of temperature, it certainly of all causes plays the most important part.
EXAMPLES FOR PRACTICE
1. How many cubic feet of air is required for the complete combustion of 1 cubic foot of: (a) propylene, C3H6? (6) butylene, C4H8? Ans.(a) 21.42 cu. ft. (b) 28.56 cu. ft.
2. Required, the volume of air necessary for the complete combustion of 8 cubic feet of gas having the following composition:
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Constituents of Gas Per Cent. Methane, CH4 72 Propane, C3H8 12 Butylene, C4H8 5 Butane, C4H10 11
Ans. 116.33+ cu. ft.
3. Required, the number of cubic feet of air necessary for the complete combustion of 23 cubic feet of Leechburg natural gas. This gas has the following composition, by volume:
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Constituents of Gas Per Cent. H 4.79 CH4 89.65 C2H4 4.39 C2H6(illegible text) .56 CO .26 CO2 .35 Ans. 216.5+ cu. ft.
