BRIDGMAN. — WATER UNDER PRESSURE. 



509 



The values of AZT and ^E found from these data are given in Table 

 XXIII. and Figure 26. Water gives out heat on passing into V, and 

 absorbs work. The work is very much less than the heat, so that the 

 internal energy of V is less than that of the liquid. 



The Curve V-VI. 



This is the last of the curves of equilibrium between two solid 

 phases. The manner in which the curve was first found has been 

 already described. The character- 

 istics of this curve are the same as 

 those ofthe other solid-solid curves ; 

 very high reaction velocity at the 

 upper end, with enormously re- 



jo 



X.25 



70 



5G5 



cc 



Q-60 



< 



55 



7^ tJ> 



-25° -IQ° -15° -10° -5' 0" 

 TEMPERATURE. 



Figure 26. The latent heat and 



»-r.20 



z 



y.l5 



< 

 -I 



a. 



z 



o 



l\ 22 23 24 25 2G 



PRESSURE, ARBITRARY UNITS. 



Figure 27. False equilibrivim at 

 low temperatures on the V-VI curve, 



the change of internal energy when V due to the slowTiess of the reaction 



passes to the liquid. 



and the viscosity of the soUds. 



tarded reaction velocity at the lower temperatures. The slowing of 

 the reaction was so great as to make impracticable the determination 

 of points lower than —25°. Anomalous results obtained once or twice 

 are to be explained by the slowness of the reaction velocity. The 

 nature of the anomaly is shown in Figure 27, plotting piston dis- 

 placement against pressure. It is as if there were two discontinuities, 

 at A and B, and so two transition points. The explanation is prob- 

 ably as follows. The reaction from VI to V starts at the upper end of 

 the steel shell. This reaction runs with increase of volume, so that the 

 layer of the new ice V may form a protecting layer over the remainder 

 of the old ice VI below. This protecting layer is capable of stand- 

 ing some appreciable stress at this high pressure and low tempera- 

 ture, so that changes of hydrostatic pressure do not reach the nest of 



