70 



BRIDGMAN. 



there is the possibihty that the impurity is dissolved in the low temper- 

 ature phase, contrary to the case for melting. Gossner gives the 

 density at room temperature as 1.898. There seem to be no other 

 values of AV or AH at atmospheric pressure. 



No other modifications were found to 12000 kgm. at 20° or 160°. 



The directly measured values of the difference of compressibility, 

 which were self consistent, indicate an abnormally large difference 

 between the two phases. The difference increases rapidly with in- 

 creasing pressure and temperature, the low temperature phase being 

 more compressible. But the measurements cannot be accurate, the 

 values being much too large, because they lead to impossibly large 



200' 



4J 



^ 180' 



imiTfHHHtftlT'l 





160" 



140° 



i ■ /' i ■ ! '! 



. i:_^^,J/__:4..,..,4 1 J 



-^-\-- V - I ■ (■■■ !■:: 



1000 2000 3000 4000 

 Pressure, kgm./cm.^ 



Potassium Sulfocyanide 



Figure 4. Potassium Sulfocyanide. The observed equilibrium pressures 

 and temperatures. 



differences of the specific heats. The direct measurements would 

 indicate that the low temperature phase has the higher expansion and 

 the higher specific heat. In addition to the measurements of the 

 difference of compressibility, the difference of expansion was measured 

 at low pressures (77 kgm.). This measurement is more moderate 

 than the high pressure ones, but also demands that the low temperature 

 form have the higher compressibility, expansion, and specific heat. 

 The values at 77 kgm. are as follows; 



Aa = -O.OeO 



A/3 = - O.O3I2 



ACp = —6.1 (kgm. cm.) 



