96 



PROF. C. FRKWEX JENKIN AND MR. D. R. PYE ON THE 



an ,l SMITH'S points lie Hose to our OW?e, bat i <-iir\r tlm.ii^li tli.'ir points 

 would be definitely flatter than ours. There is a difference of 10 Ibs. at their highest 

 pivssmv, 410 Ibs. 



CAILLETET'S figures only go up to -34 C. They do not agree very closely in 

 position or slope. 



KEONAULT'S figures lie well above the others. He states that his experiments did 

 not satisfy him. 



MOLLIER adopted a composite curve, using AMAGAT'S figures above zero and 

 REGNAULT'S below zero, modified so as to make them fit together. His curve is 

 shown dotted in fig. 18. 



An accurate determination of the pressure-temperature curve is important because 

 its gradient, dp/dS, is one of the factors in CLAPEYRON'S equation, which may be used 

 to calculate the latent heat or the vapour density. 



The gradient of MOLLIER'S curve is clearly too small, particularly at low tempe- 

 ratures. It is remarkable how large a difference in the gradient results from a very 

 small divergence between the curves. The values of dp/dd, used by CAILLETET and 

 MATHIAS(H), MOLLIER, and KUENEN and KOBSON for calculating L, and by the 

 authors who only used it for calculating the specific volume of the gas, are given 

 below : 



VALUES of dp/d9. 



The Total Heat I and Specific Heat C p of the Liquid. 



Our observations were plotted and values read from the smooth curve are given in 

 No experimental determinations of these quantities appear to have been 

 F lg ures for comparison might be deduced from MOLLIER'S (3) U diagram 

 this is beyond the range of this paper. 



The probable errors in the values of I do not exceed about per cent., from +20 C 

 a, but rise to 1 per cent, at -50 C. The presence of '073 per cent, of air 

 has no appreciable effect on the results. 



Experiments have been made by DIETERICI (15) and by MARGULES (16) on the 



