Pi:uK. c. FKi:U'KN .IKNKFN AND Ml;. l>. R, PYE OX THK 



PART L OHJECT, SCOPE, AND THEORY OF EXPERIMENTS. 



THK experiments described in the following paper were originally undertaken to 



determine the Latent Heat of Liquid C0 a and the Specific Heats of the liquid and 



of the gas at temperatures below 30 C., which is the lowest temperature for which 



MOLLIER has calculated them, and also to check MOLLIER'S Entropy-Temperature 



diagram by direct experiment, as it appeared likely that the calculated results might 



be appreciably wrong near the limits of their range. The results of the first 



experiments confirmed this expectation, and it became apparent at the same time that 



MOI.I.IKU'S 6<f> diagram could not be modified to agree with the experimental results 



without some further data. The investigation was therefore extended so as to 



include the measurement of all the quantities required for the construction 



de novo of a 6<f> diagram for saturated gas at low temperatures. Finally, by 



Sir ALFRED EWING'S suggestion, the range of the experiments was further extended 



to higher temperatures, to enable the diagram to be constructed nearly to the 



critical point. 



The experiments made to carry out this programme were : 



1. The determination of the Pressure-Temperature Curve for Saturated Vapour ; 



2. Three series of heat measurements, called Series I., II., and III., to determine 



the Latent Heat L, the Total Heat I of the liquid, and the Specific Heat of 

 the gas ; 



3. A series of throttling experiments, called Series IV., to determine the Joule- 



Thomson effect for liquid CO a ; 



4. A series of direct volumetric measurements, called Series V., to determine the 



Dilatation and Elasticity of liquid C0 a . 



Fhe experiments also supply data from which may be calculated : Specific Volume 

 'saturated vapour (or its reciprocal, the Density) ; relative Densities of liquid CO 2 

 at saturation pressures ; Specific Heat of liquid CO 3 either at constant pressure or at 

 saturation pressure. 



The pressure-temperature curve has been often observed during the last 50 years ; 



ific volume of saturated vapour and the specific heat of the liquid at 



. pressure have not been observed before below -25 C. ; the latent heat, 



heat of the gas, and the dilatation and elasticity of the liquid have not 



rved before below C. The total heat of the liquid, the specific heat 



onstant pressure, and the Joule-Thomson effect have never been 



The latent heat has often been calculated, but the specific volume 



ted vapour, on which the calculations are based, ha* not been observed 



... and only once below C., so that all calculations below -25 C are 



baaed mi axtrapplatiaaa. 



