Explosion Pressures

The propagation of the explosion-wave in gases is accompanied by a very high Explosion Pressures lasting for a very short time. The early measurements of Runsen were effected by exploding gaseous mixtures in a small cylinder fitted with a movable lid attached to a lever. The latter was weighted until the force of the explosion was unable to force the lid off. The results for hydrogen and carbon monoxide were as follow:

	Pressure
2H2 + O2	9.5 atmospheres
2CO + O2	10.1 atmospheres

Closely similar results were obtained by Berthelot and Vieille.

Modern methods consist in exploding gaseous mixtures in metallic cylinders and automatically recording the Explosion Pressures exerted against pistons working with springs. Neither the temperatures nor the pressures obtained in practice are equal to those to be expected from theoretical considerations, and several explanations have been offered, namely:

1. Dissociation of the gaseous products.
2. Incomplete combustion.
3. Variation in specific heats of gases under the special conditions, which render the theoretical calculations uncertain.
4. Loss of heat by radiation. Probably each of these factors is contributory to the main effect.