[ 174 ] 



XXVII. Experiments on the Condensation and Critical Pheno- 

 mena of some Substances and Mixtures. By Dr. J. P. 



KlJENEN *. 



1. rf^HE investigation contained in this paper is a continua- 

 JL tion of a research on •' The Condensation and the 

 Critical Phenomena of Mixtures of Ethane and Nitrous Oxide," 

 which was read before the Physical Society some time ago f. 

 The results arrived at in the latter paper were stated as 

 follows : — 



(1) All mixtures of C 2 H 6 and N 2 which contain more 

 than 01 of C 2 H 6 have critical temperatures lying beneath 

 the critical temperature of C 3 H 6 . 



(2) The vapour-pressures of the mixtures lie partly above 

 those of N 2 0, and accordingly show a maximum situated near 

 0-2 of C 2 H 6 . 



(3) This maximum does not disappear with rise of tempe- 

 rature, but remains up to the critical region ; the maximum- 

 curve reaches the plaitpoint-curve. 



(4) The mixtures ranging between 0'2 and 0*5 of C 2 H 6 

 have retrograde condensation of the second kind, all the others 

 retrograde condensation of the first kind. 



I have now discovered two more instances of mixtures with 

 similar properties, viz. mixtures of ethane and acetylene, and 

 mixtures of ethane and carbonic acid. I will begin by 

 relating some experiments which were made in connexion 

 with the former paper, and afterwards give an account of the 

 results obtained with those mixtures. 



A. On Ethane prepared by different methods. 



2. The ethane used in my former experiments had been 

 prepared from sodium acetate by electrolysis. Its vapour- 

 pressures and critical constants, especially the latter, were 

 different from those given by other observers. The different 

 values are the following, p being expressed in atmospheres : — 



DewarJ. Olszewski §. Haenlen ||. Kuenen %. 



t, . . . 35° 34° 34-5° 32-05° 



p e . . . 45-2 50-2 50 48'8 



* Communicated by the Physical Society : read June 25th, 1897. 



t Kuenen, Phil. Mag. (5) xl. pp. 173-194. 



% Phil. Mag. (5) xviii. p. 214 



§ Bulletin Ac. des Sciences de Cracovie, 1889, p. 27. 



|| Lieb. Ann. cclxxxii. p. 245. 



11 Phil. Mag. (5) xl. p. 181. 



