Plagioclase Feldspars. 589 



For component A let 



p o = vapor pressure of pure liquid at its melting point T A 



and therefore also the vapor pressure of pure solid at T v 

 (p ) T = vapor pressure of pure liquid at T. 

 (P )j. = vapor pressure of pure solid at T. 



L v = latent heat of vaporization of the liquid per mol at T. 



L s = latent heat of sublimation of the solid per mol at T. 



then from the integrated Clausius equation the following rela- 

 tion holds for the liquid : 



p ~R~ \ T T x 



{Po) T 



and for the solid 



*>' = e * 



\ T 2W 



(*.)■ 



For a liquid solution of mol fraction 1 — x, applying the 

 Kaoult's Law equation, we have then, 



R \ Ty T J 



p T = p . e .(1 — x) 



where p T is the partial vapor pressure of A over the liquid 

 solution at T. 



For a solid solution of mol fraction (1 — o?j) we have 

 similarly 



R \ T, T J 



P T = p . e .(1 — cc 1 ) 



where P T is the partial vapor pressure of A over the solid 

 solution at T. 



If T be the temperature at which this liquid solution and 

 solid solution are in equilibrium, thenp T = P T and 



Tx T ) R \ T, ~ T ) 



. (l - x) =p . e • P — #i) 



R 



Po • e 



L 8 - L v ( 1 1 



1 - X R \Ti T 



whence = e 



or 



U t) 



1 — x. 



Iz^L = , R 



where Z, = latent heat of melting (molal) of A at T. 



