156 



Mr. Harold B. Dixon on 



Rate of Explosion of Acetylene and Oxygen with excess of 

 Nitrogcfi compared luitli calculated velocities. 



§10. Lastly, I have determined the rate of explosion of 

 hydrogen and chlorine in different proportions, and com- 

 pared the rates found with the calculated velocities of 

 sound. The explosions were made in a long glass tube. 



The mean rate of explosion of dry electrolytic hydrogen 

 and chlorine was found to be 1729 metres per second. 

 About I per cent of the combustible gases were found un- 

 combined after the explosion. 



The heat of combination of hydrogen and chlorine was 

 found by Favre and Silbermann to 23,780 calories ; by J. 

 Thomsen it was found to be 22,000 calories. Berthelot 

 gives one determination 22,100 calories. The mean of 

 these numbers is 22,630 calories. Taking Thomsen's 

 number for the heat of combination, the mean rate of transla- 

 tion of the products of combustion according to Berthelot's 

 formula (corrected to 13'C) is found to be 1,551 metres per 

 second ; taking the mean number 22,630 cals. for the 

 heat of combination, Berthelot's formula gives 1,571 metres 

 for the mean rate. The rate of explosion of hydrogen and 

 chlorine under ordinary conditions is, therefore, considerably 

 faster than the rate given by Berthelot's formula. The 



