300 



PROF. C. FREWEN JENKIN AND MR. D. R. PYE ON 1 THE 



The values of the mean specific heat of the gas for 10 C. intervals have been 

 measured from the curves and are given in Table B. The pressure curves in the 00 

 chart were plotted with these values, by the method explained in Appendix I., after 

 the limit curve had been corrected by the throttle experiments. 



The values of the specific heat for each pressure at temperatures varying by 50 C. 

 intervals from 30 C. to +30 C., as measured from the curves, are given in Table C. 



Measurement of the Total Heat of Liquid C0 2 . 



The experiments described in the former paper on the total heat of the liquid CO 2 

 were not completely satisfactory for two reasons. 



(i.) The lowest temperature reached was 39 '1 C., so extrapolated values had to 

 be used for drawing the 0</> chart between 40" C. and 50 C. 



(ii.) The measurements made from 39'1 C and 35'2 C. (the two lowest),, both 

 had considerable corrections for " fall of bath temperature " and " radiation," amounting 

 together to 8.V per cent, and 5^ per cent, respectively of the measured heat. 

 Subsequent experience has shown that the correction for the " fall of bath 



70 PUMP 



FROM 

 WE/Cff/HG FLAbK 



CAL? N1L 



temperature " is liable to considerable error. It was assumed to be equal to the 

 water-equivalent of the bath multiplied by the fall of temperature during the 

 experiment. But the value of the water-equivalent of a composite body such as the 

 calorimeter, consisting of a good heat conductor surrounded by an insulator, depends 

 on the quantity of heat absorbed by the lagging, and this depends on the rate of 

 change of temperature ; as this may be very different in the actual experiment from 

 what it was when the water-equivalent was measured, the value assumed for the 

 water-equivalent may differ considerably from the effective value. 



The effect of conduction along the pipes appears also to be somewhat uncertain ; 

 the correction for this was included in the radiation correction. 



These considerations made it desirable to repeat the measurements of the total heat 

 more accurately. The method employed for this purpose was the same as before 

 (Series II., p. 72), but improved apparatus was used. By using the new 1-inch calori- 

 meter described above, radiation and conduction losses and the correction for the 

 change of temperature of the bath were eliminated, and the introduction of a heat 



