1880.J 



On the Critical Point, 



201 



Mixture of Equal Weights of Benzene and Ether. 



Temperature 215°6 225°'2 235°6 240°7 



"Volume. 



90 11-0 .... 87 .... 1-6 .... 



80 13-0 .... 10-2 . . . . 3-0 .... 



70 157 .... 13-8 .... 5-9 .... 02 



60 ....... 18-8 .... 160 .... 13-0 .... 3-4 



50 19-0 .... 20-9 .... 20'0 .... cloud 



40 21-0 .... 25-9 ..... 29-8 .... 



35 24-1 .... 29-0 .... 35-0 .... 35'0 



The critical point. — The critical temperature of benzene lies about 

 291°*7. At that temperature, no decided meniscus could be pro- 

 duced by slowly altering the volume of the substance, but the tube 

 remained full of nickering stria?. On increasing volume from 50 

 to 70, the nickering stria? disappeared, and the matter contained in 

 the tube appeared to be wholly converted into gas. On the other hand, 

 by diminishing the volume to 35 divisions, the nickering appearance 

 again vanished, for the whole of the contents of the tube were con- 

 densed to liquid. At higher temperature, no line of demarcation be- 

 tween liquid and gas was observable. 



This observation, and similar ones made with ether and with a 

 mixture of benzene, contradict the statement made by me in a 

 note published in the " Proc. Roy. Soc," vol. 30, p. 323, I 

 stated there that the temperature at which, the meniscus disappears 

 depends on the relative volumes of the liquid and gas. I have now 

 to acknowledge that the observations on which this statement were 



