1 6 FERGUSON, Studies in Capillarity 



I hope shortly to be able to discuss the results of experiments which 

 will serve to exhibit the capacities of these various methods. 



The Surface Energy of Solids. 



I do not propose here to do more than indicate one or two ways of 

 accumulating data which may serve to evaluate these important constants. 



Measurements of the surface tension in a solid-liquid surface have 

 already been attempted. The solubility of a solid in a given solvent is a 

 function of the dimensions of the solid particles, and changes by a 

 measurable amount when the particles become very small. If s is the 

 solubility for particles of radius r, and s the solubility for " large " 

 particles, then approximately 



T = - log e -. 



2 -S 



In this way the surface tension at a barium sulphate-water surface has 

 been found to be of the order 4000 dyne-cm- 1 . 



Similarly the surface tension in a solid-air surface might be measured 

 by atomising and at the same time freezing a liquid. The vapour pressure 

 outside these small particles would differ by a measurable amount from 

 that outside a plane surface ; the difference, which could be determined 

 by known methods would serve to measure the surface tension of the 

 solid. 



