BRIDGMAN. — WATER UNDER PRESSURE. 



551 



found here directly differ from those given by the formula of Tumlirz. 

 This formula, used by extrapolation, would demand a continuous in- 

 crease in the value of Gp — C^ to infinite pressures, suggesting again 

 that there is an effect entering at high pressures not taken account of 

 or foreshadowed by the behavior at lower pressures. 



+.0005 



o 



UJ 



a 



< 

 (J 



u 



: -.0005 



-.0020 



PRESSURE, KGM/CM^XIO"! 



FiGUEE 42. The change of internal energy of the liquid per kgm. rise of 

 pressure along the isothermal at 22°. 



The change of internal energy may also be found directly, 

 we have the thermodynamic relation 



For this 



The computed values are shown in Table XXXIII, and Figure 42. 

 Initially the internal energy decreases along an isothermal, but the 

 rate of decrease becomes rapidly less with rising pressure, eventually 

 changing sign, so that at the higher pressures the internal energy in- 

 creases on an isothermal with increasing pressure. This means that 

 initially the work done in compressing the water is more than lost by 

 dissipation of the high heat of compression, but at higher pressures, 

 the mechanical work per unit rise of pressure has increased so rapidly 

 because of the high pressure that part of the mechanical work ex- 

 pended in compressing the water is retained as increased potential 

 energy after temperature equilibrium has been restored. Except for a 

 region of abnormal curvature, between 2000 and 5000, which is evi- 

 dently due to the change from an abnormal to a normal liquid, the 



