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XVL On the Specific Heats of Gases at Constant Volume .—Part 11. Carbon Dioxide. 
By J, JoLY, M.A., Sc.D., F.R.S. 
Received Marcli 9,—Read April 26, 1894. 
The present paper is occupied with an experimental investigation into the variation 
of the specific heat at constant volume of carbon dioxide attending change of absolute 
density. The investigation is in continuation of a previous one,'" in which Carbon 
Dioxide, Air, and Hydrogen were the subjects of a similar enquiry over low ranges of 
density. It appeared to me desirable to extend the observations more especially in 
the case of carbon dioxide, because of the extended knowledge we already possess of 
its isothermals, and the fact that its critical temperature is within convenient reach. 
Other physical properties of the gas have also received much attention of recent 
years. It is also readily procured in a nearly pure state. 
The observations recorded in this paper extend, in the one direction, to densities, 
such that liquid is present at the lower temperature ; and in the other, to a junction 
with the highest densities of the former paper. A plotting of the new observations 
is in satisfactory agreement with the record of the old. It reveals, however, the fact 
that the linear nature of the variation of the specific heat with density, deduced from 
the former results, is not truly applicable over the new, much more extended range of 
observation. For convenience the chart at the end of this paper embraces the former 
results, and the present paper is extended to include the entire results on the variation 
of specific heat with density where the range of temperature, obtaining at each 
experiment, is approximately the same : that from air temperature to 100° C. 
Part III. of this investigation will contain an account of experiments on the varia¬ 
tion of the specific heat with temperature when the density is kept constant. The 
division is for convenience of reference. 
The value of Professor Fitzgerald’s assistance and advice, and his kindness in 
giving them to all seeking his help, are so well known, that it is needless to say that 
this present research owes much to his assistance. He is not, indeed, responsible for 
mistakes I may have fallen into, but he is to be thanked for saving me from committing 
many. 
The arrangements for carrying out the experiments are essentially the same as 
‘PM. Trans.,' A., vol. 182, 1891, pp. 73-117. 
28.12.94 
