BRIDGMAN. — "WATER UNDER PRESSURE. 



499 



have here something entirely different from the mechanism of ordinary 

 chemical reactions which produces change of reaction velocity with tem- 

 perature. For chemical reactions 





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the temperature coefficient of 

 velocity is almost universally in 

 the neighborhood of 100 per 

 cent for 10°, a value enormously 

 lower than that found here. 



The actual determination of 

 the equilibrium points was made 

 on three occasions, February .1 

 and 16, and April 20. The first 

 two were with the apparatus for 

 the middle temperature range, 



that used with the mercury. These were made with the thermostat to 

 keep the temperature constant. This apparatus was. also used to give 

 the changes of volume. The data of April 20 were taken with the low 

 temperature apparatus. The particular object of this latter set was 



TABLE XIX. 

 Latent Heat, etc., on Equilibbitjm Cttrve, Ice III-Ice V. 



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TEMPERATURE. 



Figure. 19. The change of volume 

 when V passes to III. 



to obtain as accurately as possible the slope of the transformation 

 curve, the previous data having shown that it was nearly vertical- 



The equilibrium points are shown in Table XVIII. and Figure 9. 

 The slope of the equilibrium curve is the slope given by the data of 

 April 20, but the absolute value of the pressure as given by the mean 

 of the other points is more likely to be correct. The equilibrium line 

 is straight within the limits of error. The slope is in the same direc- 

 tion as for the curve I-II, but is less. There is no possibility of this 

 line heading for the absolute zero. 



The changes of volume, four in number and taken with the mercury 



