462 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



C3 

 > 



The Solid Phases of Water — Their Relation to Each Other 



AND TO the Liquid. 



In order to present these data systematically and clearly, reference 

 is made at once to the final equilibrium diagram for water and the 



solids given at the end of 

 j)Qso | I 1.1,1 I I this paper. (Plate 1.) It 



may produce less confusion 

 in referring to this diagram 

 to state briefly the identi- 

 cal relations which must 

 be satisfied in every such 

 diagram. There are three 

 of these relations. At 

 every triple point the 

 relative positions of the 

 three equilibrium curves 

 must be such that if any 

 one is produced into the 

 region of instability, it 

 shall fall within the angle 

 made by the other two. If 

 one phase is carried into 

 another by passing across 

 an equilibrium line at con- 

 stant pressure from a low 

 to a high temperature, then 

 the reaction runs with ab- 

 sorption of heat. And, if 

 one phase is carried into 

 another by passing across 

 an equilibrium line at constant temperature from a low to a high 

 pressure, the reaction runs with decrease of volume. 



The different branches of the curves will be taken up in order, be- 

 ginning with I-L,3 I-lII, etc. The data to be given are the freezing 

 pressure at any given temperature and the change of volume. From 

 the relation between temperature and pressure on the freezing curve 

 at different points, the slope may be found, and this, combined with the 

 change of volume, gives the latent heat by Clapeyron's equation. The 

 data are presented in this order: observed change of volume, calcu- 



5 .6 

 PRESSURE. HGWl/CM^X lof 



FiGUEE 4. This shows as a function of the 

 pressure the change of volume of water on 

 passing at constant pressure from 0° to the 

 temperature indicated on the curves. 



^ Throughout, the abbreviation L will be used in referring to the liquid. 



