Mixtures of Ethane and Nitrous Oxide. 

 Fig. 5. £ = 26° C. 



x=0 



0-2 



Composition. 

 0*4 0-6 



0-8 



185 



x=! 



002 



0-004 



0-006 



c 0-008 



0-010 



0-012 



IHHHHHHH 



Hi 



HHHMBnHR 



1 IIIMIHIIiilllilllllll 



HHBflBHflH 





BBBHH 





22. The axes of coordination in fig. 2 are p and t. This 

 figure may be compared with fig. 1, which represented the 

 curves as they would have been if the phenomena had been 

 as little complicated as possible. 



The curve C^Hg — C} * s the vapour-pressure curve for ethane, 

 N 2 — C 2 the same for nitrous oxide. Ci and C 2 are the 

 critical points. CxABC 2 is the plaitpoint-curve. The curves 

 of the shape of loops are border-curves for the mixtures. 



23. There are two striking differences between fig. 1 and 



fig. 2. 



(1) The critical temperatures for a part of the mixtures 

 lie below those for the components. By adding C 2 H 6 (32°) 

 to N 2 (36°), the critical temperature is lowered to a dis- 

 proportionate extent. For a mixture containing +0*1 of 

 2 H 6 the critical temperature has gone down as far as to 32°, 

 the c. t. for pure ethane. All mixtures containing more ethane 

 than 0*1 have critical temperatures below 32°. Addition of 

 N 2 to C 2 I1 6 therefore makes the critical temperature de- 

 crease instead of increase. The lowest critical temperature 

 ( + 25*8) belongs to a mixture containing +0*5 of ethane. 



"A case like this has never been observed till now ; van der 

 Waals's theory shows the possibility of the critical tempera- 

 ture lying outside those for the components*. 



* There is one instance of a mixture, the critical temperature of which 

 lies above those for the components, observed by Dewar, namely, of CO a 

 and C 2 H 2 (Proc. Rov. Soc. of Lond. xxx. p. 543). 



Phil. Mag. S. 5. Vol. 40. No. 243. Aug. 1895. O 



