958 Dr. S. A. Shorter : Contribution to the 



means of equations (29) and (30). We have 



iiUi ^ =Vo M fS2V2 "^r' • • • (60J 



and Sl , 1 |£=V„^ + , 2 V 2 ^. . . . (61) 



OS 2 Os 2 OS 2 



These equations and also equations (58) and (59) may be 

 simplified if we assume that the vapour phase forms an ideal 

 gaseous mixture and introduce the molecular concentrations. 

 We will now consider the relation between osmotic equi- 

 librium and solubility influence. It is evident from general 

 considerations that if the addition of Ci raises (lowers) the 

 solubility of C 2 in C , the addition of C 2 to a mixture in the 

 neighbourhood of saturation raises (lowers) the osmotic 

 pressure measured by a membrane permeable to (J^ If the 

 addition of Ci raises (lowers) the ratios of the saturation 

 concentration of 2 to the concentration of d, then the 

 addition of 2 lowers (raises) the osmotic pressure of C x and 

 C 2 in the solvent medium C (i. e. the osmotic pressure 

 measured by a membrane permeable to O ). Thus if to a 

 solution of zinc chloride (Ox) and zinc oxide (C 2 ) in water 

 (O ) of composition, say, 5 1 = , 24, s 2 = *0014 |,a small amount 

 of zinc oxide be added, the osmotic pressure of the zinc oxide 

 and zinc chloride in the water is decreased. If, however, a 

 small amount of zinc oxide be added to a solution of com- 

 position, say, s 1 = 2 , 0, 5 2 = *015f, the osmotic pressure is 

 increased. 



7. Partition Equilibrium. 



We will first consider the two-phase liquid system formed 

 by two immiscible liquids C andC *, and two substances Ci 

 and C 2 , C x being soluble in C only, and C 2 being soluble in 

 both liquids. 



If s 2 * denote the concentration and f 2 * (s 2 *, p, &) the 

 chemical potential of C 2 in the * phase, the equilibrium 

 equation may be written in the form 



f 2 (s 1 ,s 2 ,p,0)=f i *(s,*,p,d) (62) 



We may regard this equation as determining s 2 * as a function 

 of 5 1? 5 2 , p, and 6. By differentiation we obtain the equations 



S21O1, s 2 , p, 6) = S 2 *(* 2 *, jt>, 6) -^— , . . (63) 



S 22 ( 5l , 52 ,^^) = S 2 *(, 2 *^,^)^, . . (64) 



where S 2 *=d/ 2 */B* 2 *. 



f See Table II. 



