256 The Earl of Berkeley on Solubility and 



Let </! ,, q 2 be the pressures on the solvent and solute 

 respectively when they are in osmotic equi- 

 librium with the solution. 

 u- } ,, u 2 be the specific volumes of the solvent and 

 solute when under pressures q x and q 2 

 respectively. 

 -<7 1 „ <r 2 be the specific volumes of the solvent and 

 solute crystals respectively, when under 

 pressure^?. 

 ■w be the specific volume of the solution when under 



pressure p. 

 BP/Bc refer to the solutions when under constant 



pressure. 

 ftPj/ttt'2 and tiT 2 /tic 1 refer to the solutions when the 

 solvent and solute respectively are under constant 

 pressures. 

 dcj/dp and dc 2 /dp be the pressure coefficients of solu- 

 bility of the solvent and solute respectively. 



This notation, unless otherwise stated, will be followed 

 throughout the communication. 



Perform a reversible isothermal cycle on the system shown 

 in fig. 3. As all terms in the final summation, other than 



Kar. 3. 



SflTURfiTCD 

 SOLUTION IN 



contact mrrt\ 



CRYSTALS 

 OF SOLUTE 



*-&*/>-■$ 



those in mSp, cancel out, it will only be necessary to consider 

 the latter. 



1st Operation. — Keeping the pressures constant, push a 

 mass m of the solvent from left to right in the figure. This 

 operation contributes no term in mBp. 



2nd Operation. — Without transference through the mem- 

 brane, increase the pressure on the left to p + Sp, and on the 

 right to 



p-? 1 +(i-'d'p 1 /bp-'d'Pi/bci.dc a /dp)$p. 



The work term on the left is 



£ r 1 /~div "ftw dc 2 \ w dc 2 c 2 doj cr^ dc^ 

 —p m p |^— - y^~ + ^ ^ j — c2 d ^ + Cl ^p Cl 2 dp 



and that on the right is 



— (p - PjXL- dPi/c^ — dPi/cV 2 • dc 2 /dp)du 1 /dq x . mSp. 



]■ 



