﻿110 Messrs. H. T. Tizard and D. R. Pye on the 



Table XIII. gives the theoretical values for the time of 

 ignition at various temperatures, calculated as already 



V11U&U ) l " 



1Y111 5 ^0 - 



J-o 

 Table XIII. 





T/T . 



1-004 



101 



1-03 



1-07 



111 



T. 



t°c. 



a( m , U(theor.). 



t (calc). 



509-5 



512-5 



522-5 



543 



563-5 



236-5 



239-5 



249-5 



270' 



290-5 



0-104 



0-069 



0-0325 



0-012 



0-0055 



0-19 sec. 

 0-13 „ 

 06 „ 

 0-022 „ 



o-oio„ 



The corresponding curve is the upper dotted curve in 

 fig. 10, the experimental values being shown by circles. 

 The general agreement is again all that could be desired. 

 Although the ignition temperature of ether is very much 

 lower than that of heptane, the temperature coefficient of 

 the combustion reaction is the same within the experimental 

 errors involved. 



XV. The experiments on carbon bisulphide were expected 

 to be of particular interest, on account of the" anomalous 

 behaviour of this substance if used as a fuel in internal 

 combustion engines. It is known that for any given fuel 

 the highest thermal efficiency obtainable is limited mainly by 

 the tendency to " detonation " at high compression ratios. It 

 is usually assumed that the tendency of any fuel to detonate 

 depends upon its ignition temperature ; the lower the 

 ignition temperature, the greater will be the tendency to 

 detonation. According to our views, the ignition temperature 

 is not a safe criterion of the tendency to detonation ; the 

 temperature coefficient is also an important factor which 

 must be taken into account The use of carbon bisulphide 

 as a fuel illustrates this point very well ; although it has a 

 lower ignition temperature than heptane, it detonates less 

 easily in internal combustion engines, and not more easily, 

 as might be supposed. We expected, therefore, to find, by the 

 experiments described in this paper, that the temperature 

 coefficient of its reaction with oxygen was very distinctly 

 lower than that of heptane and similar substances. The 

 experiments fully confirmed this, although the results do not 

 appear to be so satisfactory in all respects as those carried 

 out with heptane and ether. 



