( ^^^ ) 



p. 30). The follo\viii<>' pages niav show tliat there is also a quanti- 

 tative agreement between the phenomena and that theory. 



§ 2. In the mixture with the molecular proportion 0.1047 of 

 oxygen the meniscus b}^ increasing the volume at 21°. 86 C. appeared 

 at the top of the tube, at 21°. 94 C. it was formed at the mark 

 44.99 (stirrer below, mercury meniscus at 41.66); at 22M7 C. the 

 meniscus appeared at the bottom of the tube, at 22°. 09^ C. it was 

 formed at the mark 43.93 (stirrer below, mercury meniscus at 41.57). 

 The top of the tube was at the mark 47.40 (cm). 



In the mixture of the molecular proportion 0.1994 the meniscus 

 appeared at 13°.12 C. at the bottom of the tube, at J3°.07 C. it 

 appeared at the mark 38.5 (stirrer above, mercury meniscus at 37.4); 

 at 11°. 89 C. the meniscus appeared at the top of the tube, at 11°. 92 C. 

 it appeared at 42.3 (stirrer below, mercury meniscus at 37.7). The 

 top of the tube was at the mark 42.97. We may assume that for this 

 mixture the limits between which the meniscus appears in the tube 

 are: 13M0 C. and 11°.90 C. 



In these observations the volume from the homogeneous state was 

 increased by small variations; in this case the meniscus even without 

 stirring appears quickly at its definite place, which is not altered 

 by stirring. If on the contrary we start from the state where separation 

 into two phases occurs and the volume is decreased, the meniscus 

 only disappears after stirring and then suddenly ; hence it seems 

 that in the former case the equilibrium is established much sooner ^). 



§ 3. In order to be able to compare the observations discussed 

 above with theory, I have found what may be deduced for it if 

 ,v is supposed very small. It may be easily derived from conside- 

 rations of VAN DER Waals (Contin. II, p. 30 IT.) that the phases 

 which are in ccpiilibrium are determined by the following pair of 

 equations : 





(1) 



Here if' is the free energy for the molecular (piautily of the mixture, 

 V the molecular volume in cc, M^ the molecular weight of the 

 substance of which the quantity in the mixture is indicated by o) 



1) Compare with this wlial has been remarked in this Comm IV p. 574 about 

 the circumstanre that tlie equihbriuni was not innnedialely reached after the 

 heating of carbon dioxide at the critical point. Gomj). also Gouy, G. R. t. 116, 

 p. 1291 and Maïhias, Le Point critique des corps purs, }>. 81). 



