486 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



tory enough. The greatest difficulty was found with the A V points. 

 These are evidently irregular, but with the two other known points on 

 the curve at the triple points, the curve itself cannot be far from that 



TABLE XIII. 



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



drawn. The relation between temperature and change of volume was 

 assumed linear within the limits of error. 



Three points on this equilibrium curve were found by Tammann. 



The shape of his curve agrees 

 with that found here within the 

 limits of error, but the absolute 

 values of the pressure found by 

 Tammann are higher than those 

 given, as already explained. 

 Tammann gives no values for A V 

 on this curve. 



The values deduced from these 

 curves for All and AE are given 

 in Table XIII. and in Figure 13. 

 Very slight changes in the co- 

 ordinates of points on the equi- 

 librium curve make enormous 

 changes in the value of the slope 

 and AZT. Thus, raising the upper 

 triple point from — 17°.2 to — 17°.0 changed the calculated value of 

 AH from 94 to 64. This latter value is taken as the more nearly 

 correct, because it checks with the other values at the triple point. 



-^ 



65 



60 o 

 cc 



UJ 



< 



50 s 

 o 



45 



.22° 



-21° 



-20° -13° -18 

 TEMPERATURE. 



-17° 



Figure 13. The latent heat and the 

 change of internal energy when III 

 passes to the Uquid. 



