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



other, but the plaitpoint curve does not seem to offer any 

 peculiarities. It is hardly necessary to add, that a number of 

 combinations of substances at other temperatures might be 

 mentioned which would probably display similar phenomena. 



20. I began by preparing two mixtures of acetylene and 

 ethane containing O68 and 0*27 of the latter gas respectively. 



After having oot the constants for these two and not having 

 any more acetylene available at the time, I made new mix- 

 tures by partly exhausting the compression-tube containing 

 the 0*27 C 2 H 6 mixture and introducing fresh quantities of 

 ethane. In this manner four more mixtures were obtained. 

 Though great care was taken not to introduce any traces of 

 air into the tubes by this repeated process, it is not a safe 

 method, and the results seem to show, that some impurity 

 must have got into the mixture. Moreover, the calculation 

 of the composition of each fresh mixture was again somewhat 

 uncertain. The consequence is, that the last mixture pre- 

 pared in this manner, which, according to the calculations, 

 contained 0'7(3 C 2 H 6 , showed higher changes of vapour- 

 pressure {pe—pb) than the first mixture (^=0'68), and at 

 the same time a slightly lower critical temperature and higher 

 critical pressure. -All this does not agree with the position and 

 shape of the plaitpoint curve. The results for this mixture 

 had therefore to be rejected. This also makes the values for 

 the other three mixtures (especially the last one) doubtful. 

 It must, however, be understood that this small uncertainty 

 does not make the general result in the least doubtful, only 

 the curves would be slightly different for the mixtures if pure. 



Table VII. 

 Mixture 0-G8 C 2 H 6 -0-32 C 2 H 2 . 



t. 



n- 



Pe- 



%■ 



v e- 

 33-9 



6 97 





39-48 





7-05 



34 1 





172-5 





13115 



4035 



45-25 



134-3 



37-2 



22-2 



49 17 



51-83 



88-2 



465 



2305 





52-35 





502 



23-15 





52-40 j M 

 52-41 J m 





50-7 Ul 

 54-3 f 



23-35 







23-4 





52-32 P 





57 4 P 



23-45 



51-31 





72-9 





235 



51-33 





729 





23-55 





52-29 





591 



236 





52-22 





602 



23-65 



51-72 



5216 



672 



603 



2375 



52 



•06 C 



65 



1 



