BRIDGMAN. — WATER UNDER PRESSURE. 



497 



This completes the description of the equilibrium curves of the 

 varieties of ice already known. This last curve had not been found 

 before, and the rest of the curves to be described involve either one or 

 two of the new varieties of ice found at higher pressures. 



TABLE XVII. 

 Latent Heat, etc., on the Equilibrium Curve Ice II-Ice III. 



The CunvE III-V." 



The points on this curve were usually obtained from above, coming 

 from the region of stability of V into that of III. The reaction does 

 not usually run of itself at temperatures above — 25^; between —25° 

 and —18° it is usually possible to reduce the pressure on V as far as 

 the V-L curve, where V melts completely to water without the appear- 

 ance of III. Below —25°, however. III is pretty certain to separate 

 from V on passing slightly beyond the equilibrium curve. The points 

 were usually obtained first at low temperatures and then at higher. 

 Proceeding in this way it is easy to get the changes of volume also, 

 although this did necessitate the reaction running to completion, 

 because the reactions on this curve proved particularly sensitive to the 

 previous appearance of the phase desired. If III and V had both been 

 present recently, the reaction would run almost immediately, in either 

 direction, at any temperature, on passing over the transition curve. 



It has been already noticed that it is possible to carry both III and 

 V do^ATi into the region of stability of II. Corresponding to this pos- 

 sibility we have the realization of the prolongation of the unstable curve 

 III-V into the region of II. A point on this curve has been found at 



" For the notation V instead of IV for this new variety of ice, see p. 528. 

 VOL. XLVII. — 32 



