CLARK. — SURFACE TENSION BETWEEN LIQUIDS AND VAPORS. 381 



the liquid glycerine and olive oil are in contact with their own vapors, 

 the figures for these results being taken from Weinstein's tables.* 



Figure 14 shows the values of a in degrees per cm. 



Figure 15 shows the results of the work with the thermopile on the 

 temperature of equilibrium for the case where the vapor condenses on 

 the liquid. Experiments were conducted at temperatures between 132° 

 and 188°. It will be noticed that the equilibrium temperature corre- 



9 = 



8 



c 



5 



i 



3 



2 



i 



100 110 120 130 HO 150 100 170 180 190 200 



Figure 15. 



sponding to the normal critical temperature is 200°, the temperature at 

 which the meniscus disappeared in the liquid case. 



The curves resemble very closely the curves given by Ramsay and 

 Shields, t showing that the surface tension of a liquid in contact with its 

 own vapor obeys approximately the same laws as for a liquid in contact 

 with the vapor of another liquid. 



In closing I wish to extend my heartfelt thanks to the American 

 Academy of Arts and Sciences for their generous appropriation for the 

 apparatus used in the work, to the authorities of Clark University for 

 the opportunity of carrying on the work, and to Professor A. G. Webster 

 for his unfailing kindness and interest. 



* Weinstein, Tliermodymik and Kinetik der Korper, Vol. II, p. 4'J. 

 t Ramsay and Shields, loc. uit. 



