■604 The Earl of Barkeley and Dr. C. V. Burton on 



pressure q x ; and despite the fact that this pressure may, in 

 some cases, have a high negative value, yet we may regard 

 the differentiation as conditioned by ^i — constant; so that 



w vl^A 



The transformation required is now easily obtained as 

 follows : 



ais ° ^* (!£)** W* 



1 — ^— 1 J, equating the 



coefficients of dc a and remembering that 1 — =— — =- (see 



° Op u K 



Appendix I.), we get 



\'dc 2 J p ~\ "dp )\'dc 2 J g ~~ utic 2 ^ ■) 



The equations (8), (10), (11), and (12) can now be 

 replaced by 



"bw 



dco s 1 — iv 2 ^e 2 



dG trP T t»Pi 



s ' w Tc 2 S *°W 2 



dci _ s 2 — w c l 'dw/'dc 1 



dG ~ ~TP 2 ~ ' ^P7 



s 2 ic~— s 2 w — ^ 



(15) 



(16) 



tic 2 f tici l—c 2 's 1 



or 



ds^V^c^c^V^C: .... (18) 



Comparison of Equation (18) icith Experiment. 

 The only data suitable for verifying the equation are those 

 derived from the experimental examination of the vapour- 

 pressures of binary mixtures by Zawidski * and others ; it is 



* Zeit. Phys. Chem. vol. xxxv. pp. 129-203. 



