PRESSUKE DEVELOPED. 391 



and the pressure developed is diminished to the same extent. 

 The difference is, however, diminished by the introduction of a 

 certain quantity of inert gas, which tends of itself to lower the 

 temperature. The pressure will even be reduced proportionately 

 still more for such mixtures than for explosive mixtures con- 

 taining no inert gases. 



11. This is confirmed by experience. As far back as 1861, 

 Him measured the pressure developed by the combustion of air 

 mixed with one-tenth of its volume of hydrogen, and he found 

 3*25 atm., instead of 5*14 atm.. The reduction would be about 

 one-third, instead of being greater than the half, as with pure 

 oxygen. 



Mallard made similar observations 1 on various mixtures of 

 air and combustible gases. 



Finally may be cited the recent experiments of Mallard 

 and Le Chatelier on the pressures developed by mixtures of 

 air and methane, and also on mixtures of air and coal gas. 2 

 The measurements of these authors were effected by means 

 of a hollow spring, which served as a registering manometer 

 and communicated with a combustion chamber of 4 litres 

 capacity. 



atm. 



0-94 (CO + 0) mixed with 0-06 of inert gas (nitrogen and water vapour) 8-6 



0-31 (CO + 6) 0-66 of C0 2 , 0-02, 0-01 water vapour 6-0 



0-955 (H 2 + 0) 0-03 N + 0-015 water vapour 9-2 



0-67 0-32 + 0-01 8-3 



0-65 0-34 H + 0-01 8-1 



0-49 0-490 + 0-02 7-2 



0-32 0-67 H + 0-01 6-3 



0-33 0-65 N + 0-02 6-3 



0-19 0-54 H + 0-25 N + 0-02 water vapour 5-15 



0-17 0-14 H + 0-69 N + 0-02 5-0 



0-95 (H + Cl) 0-03 H + 0-02 water vapour 8-1 



0-74 0-25 C1 + 0-01 7-1 



0-51 0-47 H + 0-02 7-0 



0-41 0-59 H + 0-01 6-0 



The detonating mixture with a methane base (CH 4 + 4 ), 

 mixed with three times its volume of air, gave pressures ap- 

 proaching 7 atm. 



With the same mixture, when pure, the figure rose to 14 atm. 



The following is a table of some observations which M. 

 Vieille and the author made by means of a movable piston : 



I. Mixture of two combustible gases. 



atm. 



CO + H 2 +0 2 7-8 



2CO + H 6 + 6 8-3 



C2H 4 +H 2 + 7 13-3 



1 " Annales des Mines," torn. vii. 1871. 



8 " Journal de Physique," 2 e se'rie, torn. i. p. 182. 



