BRIDGMAN. — WATER UNDER PRESSURE. 525 



when the reaction runs in the direction in which the symbols read. At 

 every point, the sum of the two smaller changes is equal to the larger. 



An adjustment was necessary in seven out of thirteen possibilities. 

 The average adjustment was about 5 parts in 10,000 ; the maximum, 7 

 parts in 10,000 of the original volume. The points on the III-L curve 

 were so difficult to obtain, as already explained, that the entire course 

 of this curve was in large measure determined by the behavior at the 

 two triple points at either end. 



With regard to the values for the latent heat and the change of 

 internal energy, there was room for more difference of opinion as to the 

 best way of making the adjustment. The latent heat, given by the 



formula ^H = T^v -J-, is seen to depend on the change of volume, 



already fixed, and on the slope of the equilibrium curve. The slope 

 was detennined graphically from the equilibrium curves. There is 

 chance for considerable error here, and the possibility of introducing 

 comparatively large changes into AZf by a very slight raising or low- 

 ering of the equilibrium curve, too slight in all cases except that of 

 III-L mentioned to introduce a perceptible change in the co-ordinates 

 of the triple point. On the equilibrium curves solid-solid, which run 

 approximately vertically, the latent heat is usually so small as to have 

 very little effect in the adjustment. It was possible to determine this 

 latent heat with a fair degree of accuracy, however, and so this was left 

 without adjustment, the other values being adjusted so as to be consis- 

 tent with it. 



Evidently when the values of the latent heat are properly adjusted, 

 the values of the internal energy will also be consistent, because these 

 differ from the latent heat only by a quantity involving the change of 

 volume, which is already consistent at the triple point. 



The tables already given, under the equilibrium curves separately, 

 enable an estimate to be formed of the amount of adjustment necessary, 



dp dv 



Two values are listed both for -7- and A^. The first value of ~ was 



dt dt 



obtained directly by graphical construction from the equilibrium curves, 



and from this the first value of A// was calculated directly, point by 



point. The final value given for t^H is the value taken from smooth 



curves so drawn as to check at the triple points. From this final value 



of Afl^'the final value of ~- was calculated, and listed in the column 



dt 



of final values. Table XXIX. gives the values of Af/ at the triple 



points. The III-L curve is the only one that it was necessary to juggle 



with in any way, and this has already been explained. The symbols 



