Mandicster Memoirs, Vol. Hi. (1907). 7 



also point out that there is nothing novel in M. Crussard's 

 idea of working backwards from the explosion rate. One 

 of our members, Mr, D. L. Chapman * has calculated the 

 specific heats of gases from the explosion-rates by means 

 of equations deduced from Riemann's formula for the 

 propagation of a compression wave. 



Until lately no one had measured directly the specific 

 heat of a gas at temperatures beyond 200"C. The un- 

 expectedly low pressures found by Bunsen in the explosion 

 of gases, were attributed by him to the dissociation of the 

 products, by Berthelot and by Le Chatelier to the great 

 rise in their specific heats. Either hypothesis would 

 account for the observed pressures. Dugald Clerk added 

 a third explanation — that the gases combined compara- 

 tively slowly, and that heat was lost by conduction, etc., 

 while the chemical combustion was still proceeding. The 

 specific heats deduced from the pressure curves of exploded 

 gases at high temperatures, did not appear on the pro- 

 longation of the curves drawn, for instance, for CO2 or 

 steam at low temperatures ; hence the doubt as to what 

 happens at high temperatures, and the necessity for 

 making determinations at intermediate temperatures. 

 The specific heat of air was determined up to 900'^C. by 

 a resonance method in an open tube by Stevens, but his 

 results, which show a distinct rise, have been questioned 

 by A. Kalahne,"!" who with an improved apparatus finds a 

 much smaller increase. 



I have directly determined the specific heat of CO., 

 by heating the compressed gas in a steel bomb and 

 dropping it into a specially constructed calorimeter. The 

 rise in the specific heat is undoubted, but the experiments 



* D. L. Chapman, "On the Rate of Explosion in Gases." Phil. Mag., 

 Jan., 1899. 



t DriidSs A/ui., xi., 225. 



