.0,31833 



Journal of the Mitchell Society. [June 



THE VALUE OF p AT THE CRITICAL TEMPERATURE. 



It is possible to extend this proof quite to the critical tem- 

 perature itself. Substituting- in equation 9 the value of L 

 given by the thermodynamical equation 2, and the value of 

 E : = .0,3183 P V - : \ we have 



[io] r-r-A = " 



and obtaining the limit of this equation as V approaches v in 

 value we have for the equation at the critical temperature, 

 where V = v, the form 



[11] .0 4 955V*i T^-P = ,»'. 



\ / 



8 P 



As we have shown the most correct value for the -«= availa- 



o 1 



: this temperature is that given by equation 4 and sub- 

 stituting: this value in the equation we g-et. 



11 Q'M T 

 [12] m' = V 1 * -LL_z^± _ .o 955 P V 



This equation is the same as equation 17 of the third paper 1 . 

 Here V. T. and P. are the critical volume, temperature, and 

 pressure respectively, and ;;; is the molecular weigfht of the 

 substance under consideration. The equation is interesting: 

 because a method for calculating: the constant of 



molecular attraction. /i'. in terms of the critical constants and 

 the molecular weig:ht of the substance. Since the molecular 

 weight enters into the equation it evidently cannot be applied 

 to associated substances. Again using: the critical data, 

 already referred to. given by Young-, the values obtained 

 from this equation are shown in Table 2 above. Except for 

 di-isobutyl, normal heptane, normal octane, methyl acetate, 



-Jour. Phvs. Chem., Dec., 1904. 



