( 278 ) 



-Cr) -''''■ 



fTdp\ 

 According to Keesom's observations the value of I — — 1 tor the 



— 1 =6,7 (the value found for carbonic acid) — f ^ ) = 3,921 



beginning of the plaitpoint line is equal to — 6,3 for .x- = 0,1047, 

 and equal to — 6,08 for .i' = 0,1995. From this we calculate, with 



pK^- 



and 3,824 — so more than double the value which follows from 



the equation of state, when we put there b independent of the volume. 



The values given by Keesom for pressure and temperature oï the 



critical tangent point, and of the critical point of the unsplit mixture, 



1 f^p\ 

 furnish a means to test the reliability of the value of — v- , as 



p \pxJvT 



it has been calculated from his observations. 



For the mixture x = 0,1047, hj) amounted to 9,9 for the critical 

 tangent pressure and AT to — 7,69 for the critical tangent temperature. 



If we again write for this homogeneous phase : 



dp z= f-^^ dT + (/] dx 



or 



we find 



1 dp _(T ^p\ dT 1 /ÖA 

 p dx \p hT Jcx Tdx p \dxJvT^ 



9,9 ^ g ^ - 7,69 1 fdp-^ 



72,93 X 0,1047 304,02 X 0,1047 ' p \dxJ^T 



or 



1,297 + 1,62 = -!/ I =2,917. 

 P \dxJi,T 



And from the observations for x = 0,1994 



16,72 , ^ - 14,71 , 1 fdp 



72,93 X 0,1944 ' 304,02 X 0,1994 ' p \d 

 or 



1 f dp 





1,15 -f 1,635 = - -^ = 2,785. 



P \OxJi.T 



For the homogeneous phase of the critical circumstances of the 

 unsplit mixture which cannot be realized, Keesom found Ap = — 5,23 

 and liT= — 18,34 by the application of the law of the corresponding 

 states. From these data we find: 



— 5,23 — 18,34 1 /d/> 



72,93 X 0,1047 304,02 X 0,1047 ' p \dxj,2' 



or 



