328 



REPORTS ON THE STATE OF SCIENCE. 



upper limit of whicli may be put at about 2000' C. ; though it is 

 probable that 2500' or more is occasionally reached locally. Langen, 

 however, places the upper limit of the application of his formulre at 

 1700° C, on the ground that there is dissociation of the CO^ at higher 

 temperatures than that. There does not seem to be much reason for this 

 limitation, for the eflfects of dissociation (provided that equilibrium is 

 attained) are indistinguishable from those of increasing specific heat, and 

 should be included in the change of energy. Dissociation may give 

 rise to errors in the temperature measurement, but there is reason to 

 suppose that the dissociation which occurs in the COj in steam at a 

 temperature of 2000° C. is too small to cause any material change of 

 volume, though it may mean considerable absorption of heat. 



The formula; given by Langen as representing the results of his 

 observations are as follows :— 



Air = 4-8 + 00006!' 

 CO, C = 6-7 + 000260 t 

 Ufi C = 5-9 + 000215 t 



where C is the mean thermal capacity over the range to t° C. The 

 explosion pressures predicted by the use of these formula agree well with 

 the observed pressures except in the case of mixtures of CO and air, 

 where they are a good deal too high. In the other cases the maximum 

 deviation is about 4 per cent. 



Mallard and Le Chatelier represent their results by formulae which 

 differ greatly from the above in the case of COj and H2O, though the 

 formula for air is the same. This discrepancy must be due in some way 

 to the method of reduction adopted, for, as already pointed out, the 

 explosion pressures reached with mixtures of the same composition are 

 very nearly the same. 



Taking Langen's values, the following table exhibits the energy of the 

 various simple gases, and of the mixture on which Clerk experimented, at 

 1600° and 2000° respectively. The energy of the same gases at 800° and 

 at 1200° based on Holborn and Henning's and on Clerk's results is also 

 given for compai'ison. The results are given in calories per gramme 

 molecule. To reduce to foot-pounds per cubic foot multiply by the 

 factor 3"96. 



* C-49. 



