COMPARISON BETWEEN THEORY AND OBSERVATION. 507 



reactions cannot in general be admitted during the period of 

 rapid cooling succeeding combustion. 



19. Let us now compare the volume of the gases liberated. 

 The reactions of powder, according to the table on page 506, 

 liberate a volume of gas greater in proportion as they develop 

 less heat. 



The minimum of gaseous volume (22*3 litres) corresponds to 

 the thermal maximum (100*0 Cal.), and vice versa (66'9 litres 

 and 11-4 Cal.). 



The gases may also vary from the single to the double, the 

 heats only changing by a fifth, with the exception, however, of 

 the transformation (6). 



20. Hence follows this interesting consequence, that the 

 theoretical pressure appears to be the greatest for the transforma- 

 tion liberating the least heat (except 6) ; it would, on the con- 

 trary, be the smallest for that liberating the most. 



In fact, several transformations take place at the same time 

 owing to locarconditions of temperature, dissociation, and relative 

 rapidity of combination. The heat liberated, the volume of 

 gases, and therefore the pressure, will consequently remain inter- 

 mediate between these extreme limits. 



4. Comparison between Theory and Observation. 



1. Such are the general consequences of the theory. We are 

 about to show that observation confirms these consequences by 

 summing up the results of the experiments, especially of those 

 made by Noble and Abel, which have been carried out with 

 greater care than any others. 



2. Take first the mean equation (p. 498) 



16KN0 3 + 210 + 7S = 13C0 2 + 3CO + 5K 2 C0 3 + K 2 S0 4 



+ 2K 2 S 3 + 16N. 

 Equation (1) x 2 + eq. (5) X 1 + eq. (3) x 3 + eq. (2) + 2. 



Further, it is supposed that the excess of sulphur has been 

 changed into trisulphide, K^. 



According to this mean equation, 964 grms. of matter would 

 have yielded 674'5 Cal. at constant volume, developing 290'1 

 litres ; or, for 1 kgm., 697 Cal. and 300 litres. 



4350 atm. 



The theoretical pressure would be TTT^r- 



n O'Zb 



3. Take, now, the transformation observed which produced 

 the most carbonate and carbonic oxide, that is to say, the 

 following system : 



Equation (1) X J + eq. (2) X J + eq. (3) X . 



We should have had in this case, for 120 '8 grms. of imatter, 

 815 Cal. and 363 litres of gas ; or, for 1 kgm., 674'5 Cal. and 

 300*5 litres. These are practically the same figures as above. 



