Critical Phenomena of Ether. 



817 



opalescent material but also upon the difference o£ optical 

 density between that material and the surrounding medium. 

 Since the optical densities of the liquid and vapour, however, 

 tend to equalize with increasing rapidity as C is approached, 

 the sharpness of the point of disappearance would be still 

 further accentuated. 



It was observed that the intensity of the opalescence above 

 the Cagniard-Latour temperature decreased rapidly at first 

 with rise of temperature, but with diminishing rapidity as 

 the temperature became higher. To obtain some experi- 

 mental record a rough graph showing the intensity of the 

 opalescence at various temperatures was made in the following- 

 manner. A number of tubes of similar dimensions were 

 rilled with water containing a proportion of milk varying 

 from 0'02 to 10 per cent. If one of these was held before 

 the plate-glass observation window in a suitable position and 

 under suitable conditions of illumination, an image could be 

 obtained, close to the experimental tube, which resembled 

 very closely a tube of opalescent ether. The series of tubes 

 formed a rough scale of opalescence, with which the opalescent 

 ether was compared at various temperatures. In fig. 7 the 



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ordinates represent the intensity of the opalescence in terms 

 of the proportion of milk contained in the tube whose image 

 matched it most nearly (10 per cent, milk = 100) . The curve 

 shows sufficiently well the manner in which the opalescence 

 varied with the temperature, and the form of the curve is 

 altogether different in character from that of fig. 6. 



The curve of opalescence is rather of the character which 

 might be predicted from Krister's theory. According to that 

 theory, there would probably be some connexion between 

 the intensity of the opalescence and the distribution of velo- 

 cities of translation according to Maxwell's theorem. The 



