﻿Ignition of Gases by Sudden Compression. 121 



frequency of atomic oscillation is high is in agreement with 

 our general knowledge of the hydrogen molecule. In spite, 

 therefore, of the strong arguments that have been brought 

 forward against the radiation theory of chemical reactions, 

 these results support the view that there is a connexion, 

 even though an indirect one, between the temperature co- 

 efficients of gaseous reactions and the infra-red spectra of 

 the reacting substances. 



XXI. The results of this investigation may be summarized 

 as follows : — 



(a) Quantitative experiments confirm the view that at the 

 lowest ignition temperature the heat evolved by the 

 combustion of a gas just exceeds that lost to the 

 surroundings. 



(6) From measurements of the rate of loss of heat just 

 below the ignition temperature, and of the intervals 

 between the end of compression and the occurrence 

 of ignition at different temperatures, it is possible to 

 deduce the temperature coefficient of the gaseous 

 reaction. 



(c) The temperature coefficients so obtained are confirmed 



by the increase in the minimum ignition temperature 

 which is observed when the gas is in a turbulent 

 state. 



(d) The results show that the temperature coefficient of 



the combustion of carbon bisulphide is much lower 

 than that of heptane or ether. This is in agreement 

 with the relative tendencies of these fuels to detonate 

 in an internal combustion engine. 



(e) The results do not agree with the radiation theory of 



chemical reaction. 

 (/) Some evidence is put forward to show that the rate 

 of reaction on sudden compression is independent 

 within wide limits of the concentration of the com- 

 bustible gas, but only depends on the amount of 

 oxygen present. This evidence is, however, incom- 

 plete. 



We are greatly indebted to Messrs. Ricardo & Co. for the 

 loan of their apparatus and for much additional assistance ; 

 also to the Department of Scientific and Industrial Research 

 for a grant towards the expenses of the investigation. We 

 also take this opportunity of thanking Mr. C. T. Travers for 

 his help in carrying out some of the experiments. 



