500 BEPOET— 1888. 



authors with different explosive mixtares, including as combustibles 

 hydrocarbons, cyanogen, and carbon monoxide and nitrons oxide as 

 oxidisers ; and the results of mixing the explosive mixture with an inert 

 gas are investigated and the experimental results discussed.' A summary 

 of the experimental methods, results, and conclusions drawn from them 

 are given in ' Ann. Chim.' (6), 4, 1885, pp. 13-90. 



The apparatus used for the explosions was a spJierical steel bomb 

 provided with a very exactly fitting piston of known mass and section, 

 by means of which, as it moves under the influence of the pressures 

 developed during the explosion, the motion of a point rigidly connected 

 with it is recorded on a cylinder rotating in a period of about two 

 thousandth parts of a second. The readings were taken at intervals of 

 four ten-thousandths of a second, each interval corresponding in one set 

 of experiments to 5 mm. on a circular section of the cylinder as it rotates 

 round its axis with uniform motion ; at intervals of 15 mm. in another set. 



Calling lines parallel to tbe circular section of the cylinder abscissae 

 and lines parallel to the axis ordinates, values of 8j/ for successive in- 

 tervals of time St are easily got, for intervals, say, of time 8t correspond- 

 ing to 6 mm. ; and again from this row of values of 8y, values of S^y for 



equal intervals of time Bt are found ; thus a series of ratios ^ are ob- 



tained. The greatest value of these ratios combined with the mass of 

 the piston is the maximum force exerted on tlie base of the piston during 

 the explosion, whence, from the known mass and section of the piston, 

 the pressure per square cm. is deduced. Thus successive pressures 

 during the explosion, and in particular the maximum pressure, are 

 known. 



It is noticeable that Berthelot and Vieille account for the difference 

 between the pressure got by Mallard and Le Chatelier 9'95 atmos. and 

 their own value lO'l for the explosion of CO + by the statement that 

 their number, lO'l, was got with dry gases, while the lower number was 

 the result of exploding in a mixture containing vapour of water ; they 

 point also to the fact that Bunsen obtained 10"5 atmos , which agreed with 

 theirs better than with Mallard and Le Chatelier's number. But it is 

 probable that the lower number is more nearly correct, as Dixon has 

 shown 2 that the results of exploding CO and O partially dried are un- 

 certain, varying according to the amount of the trace of water-vapour 

 present, and that a perfectly dry mixture of the gases cannot be exploded 

 by sparks from an induction-coil. 



The following are among the results obtained for temperatures up to 

 3000° and even getting on to 4000° (air-thermometer) : — 



The specific heats of gases are indejjendent of the density or of the 

 volume of unit mass at these high temperatures, as is the case near 0°. 

 The apparent specific heat (of a gas or a gaseous mixture) increases as 

 the amount of heat absorbed increases. These conclusions (p. 58) are 

 arrived at independently of any hypothesis about laws of gases and their 

 physical constitution, i.e., independent of Avogadro's hypothesis and of 

 any views as to the molecular constitution, and without assuming the 

 applicability of Boyle's and Gay-Lussac's laws (p. 51). 



Mallard and Le Chatelier did not give results for the highest pressures 

 (and temperatures) given by the explosions ; but for temperatures up to 



• C. R. 94, p. 822 ; 95, pp. 151, 199. = Phil. Trans. 1884. 



