300 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



one starts with, one is led by this method of successive approximations 

 to something much like Knoblauch's curve in the end. 



The second conclusion that can be drawn from Figure 12 is that 

 the true saturation curve, although close to Knoblauch's curve, prob- 

 ably runs somewhat higher in the range covered by these computations. 



100 



200 



t 300 



Figure 13. Values of Cp computed by Planck's method from Linde's 

 characteristic equation. The circles come from an H formula based wholly 

 on Knoblauch's C p measurements, the crosses from a similar H formula 

 based wholly on Thomas' C p measurements. Both confirm Knoblauch's 

 saturation curve (K) rather than Thomas' (7 1 ). 



It will be remembered that the same conclusion was reached in two 

 different ways in the last subsection (pages 290 and 293), and that it 

 is further confirmed by the fact that Regnault's values near saturation 

 at atmospheric pressure are higher than Knoblauch's. 



The volume measurements of Ramsay and Young and of Battelli are 

 not so conveniently arranged for the purposes of this particular compu- 

 tation. In both cases the temperature was held constant while the 

 pressure and volume were varied. In the case of Ramsay and Young 

 it is possible to rearrange the data so as to give approximate isochors 



