236 MR. W. F. G. SWANN ON THE SPECIFIC HEATS OF AIR AND 



Table II. Steam Temperature. 



Mean value for the specific heat at 100 C. = 0' 22097 cal. per gr. degree. 



Since all the measurements on August 30 were made with gas from a half-spent 

 bottle, the specific heat could be most simply calculated by taking the mean values of 

 CE/S0 and Q from the set of experiments 1, 2, 3, and combining them with the mean 

 values from the set 4, 5. For this reason the value of S, calculated from the 

 experiments on August 30, is given double weight in calculating the mean value of S. 



The determinations of the specific heat made with bottles which were full at the 

 commencement of the runs do not show sufficiently definite deviations from those 

 made with bottles which were nearly empty to warrant grouping them separately > 

 it is interesting to observe, however, that the effect of the presence of air can 

 occasionally be detected in the observations, for example, in the case of the experi- 

 ments performed on August 21, the observations for Experiment 1 were taken after 

 the bottle had been running for 40 minutes, while those for Experiment 2 were taken 

 after it had been running about 20 minutes longer. If the values of CE/S0 are 

 calculated, it will be seen that in Experiment 2 the value of CE/S0 has increased 

 while that of Q has decreased, indicating that as the CO 2 became purer, the specific 

 heat increased ; the fact that the value of S calculated from 1 and 4 does not come 

 out less than the value calculated from 2 and 3 may be due to the bottle 2 in 

 Experiment 4 containing CO 3 , which was less pure than that contained by bottle 1 

 in Experiment 1. 



