( 277 ) 



If we put, as is I'oniul with coiislant value of h, ?; = 3è and 



8 a 

 MRT=—:-, we liiul tlic value aiveii above: 



a a ^ 



d Ion — /fZ loq 



dlogT __ •' h 9 1 ^ h^l^ 



da\ dx 16 diV,Q 



In what precedes the relation between the variation of T, and that 



of X has been discussed for the beginning of the plaitpoint line. Let 



ns now proceed to the discussion of the relation between the variation 



of p and that of T. 



dp 

 From the en nation of — ffiven above, we deri^'e : 



\p dTj,^ p ydTj,,'^ p \d.vJ„T dT ' 



Now in the critical point of a component I Ty, I is eqnal to — 



Tdp 



for the saturated vapour tension. And for numerous substances — -— 



' p dl 



for the saturated vapour tension is about 7 in the critical point. 



Td.v. 1 f dp 



- now being- known, we want still the knowledge of 



dT " ^ ' ^ pK^'^JvT 



fT dp \ 

 for the calculation of — — r, for the plaitpoint Ime. 



1 /d/A 

 We can calculate — [^ \ by means of the equation of state. 



P K^^'iJoT 



If we put again h constant, we tind the value indicated above : 

 1 f^p\ 1 ( MRT db da 1 I 



p \dtvJvT P [{v — by dw d,vv^\ 

 or 



a 

 1 fdp\ . 't? i S 1 db v^ 1 da. 



fdp\ 



p \d.vJvT p [27 b dx{v — by a dx\ 



1 n 



With u = 36 and p ■= —— we should find for carbonic acid and 



oxygen 



or 



1) See page 273. 



-(^-f] = 3 X (0,493 -f 0,0903) ') 



