816 Mr. F. B. Young on the 



respectively, then the proportion by volume of the liquid 

 present is given by 



v uui — wV 



Figure 6 shows the graph of -^ with temperature when V 



is greater than Y c . The graph is plotted from the experi- 

 mental values of u and u } given by Ramsay and Young (20), 



Fig. 6. 



*. 



s<r 



Ic, O 



icjH"C 



T.«.i, 



V being taken as 4*5, but its shape is characteristic of 



such a graph derived from a saturation curve of the form 



given in Andrews's diagram, i. e. a simple curve of negative 



curvature. It shows that the volume of the liquid diminishes 



with increasing rapidity, the temperature of disappearance 



being sharply marked. A similar graph would be obtained 



Y—v 

 by plotting — ==- with temperature in the case where 



V<V C . According to Altschul's simple explanation, either 

 the bulk of opalescent material present should disappear in a 

 similar manner with increasing rapidity and a well-marked 

 point of disappearance, or the accepted form of the saturation 

 curve requires modification and that curve must be given a 

 peaked form. The assumptions of Donnan concerning 

 surface-tension do not seem greatly to affect the nature of 

 the graph. The optical intensity of the opalescence will, it 

 is true, doubtless depend not only upon the bulk of the 



