260 



MOREY 



ART. G 



respectively, gives the value of 6.06 as the constant coefficient 

 of the second term. The equation now becomes 



dp ^ (t?" - V) - 6.06 {-n^ - 7?0 

 lit ~ {V - vO - 6.06 (v'' - v'Y 



The numerator of this is always positive. The entropy differ- 

 ence (vapor — tetrahydrate) is always positive. The entropy 

 difference (hexahydrate — tetrahydrate) is negative, since the 



./ .2 .3 ^ .S £ 



COMPOSITION W H'£l6//rPe/rC£fT 



-•Kc? -20 o 20 ao 



TeMeeKATUKE /N DEGPeSS CENTIGRADE 



Fig. 3. The binary system, H20-CaCl2. Diagrams .4, B, and C are 

 the projections of the curves representing univariant equilibria in the 

 solid f-i-x model on the p-x, p-i, and t-x planes, respectively. 



decomposition of hexahydrate into tetrahydrate and solution, 

 to be considered later, absorbs heat, and this negative term is 

 multiplied by a negative coefficient, making the second term 

 positive. The denominator is large and positive, because of the 

 very large specific volume of the vapor. The value of dyjdt is 

 consequently positive, and the pressure increases with the 

 temperature, as is the case with the dissociation pressure 

 of the hexahydrate. It is to be observed that this equilib- 



