#96 Inversion-Points for Fluid passing through Porous Plug. 



note, however, that the experimental points for C0 2 corre- 

 spond to a range of temperatures lying on the lower portion 

 of the theoretic curve ; while those for N lie on the upper 

 part. These facts tend to substantiate the claim put forward 

 in my previous paper that there are probably two inversion- 

 points corresponding to each pressure. This point is of im- 

 portance ; for whereas other investigators have readily 

 admitted that the inversion-point varies with pressure, yet 

 T believe there is a tendency to regard the two-fold value 

 for each pressure as merely a result of pressing to more 

 than a legitimate extent the validity of the theoretic equations 

 which had been considered. 



The inversion-points have also been calculated for other 

 gases. Those for isopentane, ethylene, and ether lie on the 

 lower part of the inversion-curve, and the curve for C0 2 

 passes nearly through them all. 



General properties of the Equation of State 



RT -_A_ 



£>= = e itT'V 



v — b 



The fact that by a proper choice of n a very much closer 

 agreement can be obtained, warrants one in further examining 

 the general properties of the family of curves for which n is 

 the parameter. 



Whatever the value of n may be, this equation indicates the 

 existence of critical phenomena. 



If n is the same for all gases, there are three constants 

 which may be different for different gases ; hence, with the 

 same restriction the law of corresponding states will be 

 satisfied. The reduced equation is 



<2/3-l) = 7 exp,{2(l-A)}. 

 The equation connecting ft and 7 at an inversion-point is 



£t(7*--4(n+l)] = --2(n + l); 

 and the equation between a and 7 is 



«7~' = [4(„ + 1) ~rl exp. { 2 (£±| - !„)} . 



For each value of n there is a maximum pressure for which 

 inversion can occur ; this is given by the value of a corre- 

 sponding to 7'* = 4 ; hence the maximum value of « for anv 



