SURFACE TENSION AT THE INTERFACE BETWEEN 

 CERTAIN LIQUIDS AND VAPORS. 



By Arthur L. Clark. 



Presented by A. G. Webster, May 10, 1905. Received Oct. 11, 1905. 



All determinations of the capillary constants of liquids are made 

 necessarily with the liquid used in contact with its saturated vapor, a gas, 

 or another liquid. The constant for a free liquid surface, i.e., one not 

 in contact with any other substance, cannot be determined, although the 

 value for a liquid near its freezing-point and in contact with its own 

 vapor cannot be far from the true value. It is true, however, that almost 

 all methods for the determination of the constant measure the tension at 

 the line of contact with a solid and not on the undisturbed surface. 



The values of the constant for various liquids have been determined by 

 a large number of observers.* Quincke f has determined the constant 

 for the interface of two different liquids, and Kundt | for liquids in con- 

 tact with gases under pressure. Both of these observers worked at room 

 temperatures. Quincke found that a 1 < a 2 + a 12 , because of solution of 

 the two liquids in each other. Kundt found that the surface tension be- 

 tween a liquid and a gas decreases rapidly with increasing pressure. 

 Wroblewski § showed that this effect was due to solution of the gas in 

 the liquid. Since the surface tension of mixtures obeys approximately 

 the centre of mass law, we can readily see that we must have a very 

 great lowering of the capillary constant, when one liquid is replaced by a 

 gas whose surface tension is practically zero. 



A very large number of experimenters || have investigated the effect of 

 raising the temperature of a substance upon its capillary constant, and 

 have found that, in every case, a rise in temperature is accompanied by a 



* See Winkelmann, Handbuch der Physik, Vol. l.page 497, for a very complete 

 bibliography of the subject. 



t Quincke, Pogg. Ann., 139, 1 (1870). 



t Kundt, Wied. Ann., 12, 538 (1881). 



§ Wroblewski, Compt. Rend., 95, 284 (1882). 



II See Winkelmann, Handbuch der Physik, loc. cit. 



