194 Dr. J. P. Kuenen on the Condensation and Critical 



'di 



purpose. If we put in the general equation for ( ,y) in (32) 



"dx 



I -j- ) = co , we find \-jr\ = =o , because at A neither - 



=rf- is 0, the direction of the p line not coinciding with 



By ft 



either the v or the x axis. 



34. From (J-) = co at A it follows, that the plaitpoint curve 



has a vertical tangent at A and the loop for the mixture of 

 minimum critical temperature touches the plaitpoint curve at 

 A in the ordinary manner. In my former paper I drew the plait- 

 point curve with a break at A, as suggested by the experimental 

 data, and drew some conclusions from this which now appear 

 to have been erroneous. The two branches of the connodal 

 curve at the moment of the division of the plait intersect as 

 two straight lines. This was not sufficiently brought out in the 

 diagram (fig. 11) *. Moreover the curves were drawn in such a 

 manner, that a line parallel to the v-axis had, under certain 

 circumstances, four points of intersection. This was an unne- 

 cessary assumption which, in cases of splitting up of the first 

 plait, is not a probable one. Altogether the paragraphs 40— 

 42 with the figures 7, 11, and 12 should be withdrawn. 



35. All these results are entirely independent of the form 

 of the equation between p, v, and T for the mixtures. We 

 will now apply van der Waals's equation for some calculations 

 regarding the mixtures investigated. 



The equation between p, v, and T has the form 



(*+£)(«-k)=BT, 



in which a x and b x depend on the composition of the mixture 

 x in the following: manner : — 



a x — a i(l — ^) 2 + 2a 12 A'(l — x) +a 2 x 



b x = b 1 {l-x) 2 + 2b 12 x{l-x) + b 2 x 2 ^ ; 



«!,/>! being the constants for the first and a 2 . b 2 for the second 

 substance ; a 12 is the attraction-constant between the two 

 substances, b n the volume-constant for the combination. 

 According to the simple suppositions underlying the deduction 

 of the formula, we should have : 



v%=i{ to,+ ln> 2 ). 



* Kuenen, I. c. p. 192. 



t Lorentz, Wied. Ann. xii. p. 134. 



