A NEW THEORY OF COHESION 



APPLIED TO THE THERMODYNAMICS OF 



LIQiJIDS AND SOLIDS. 



• 



By Harold Whiting. 



Presented by invitation, March :2, 1SS4. 



§ I. The phenomena of surface tension, elasticity and 

 latent heat prove that between the particles of matter, 

 whatever they may be, there is an attraction which must 

 be some function of the distance between them. It is this 

 attraction against which work is done by expansion; and 

 since work is the product of force and distance, we may 

 obtain a measure of cohesion when we know the coeffi- 

 cient of expansion and the difference of the specific heats 

 of a body under constant pressure and under constant 

 volume. 



The latter, unfortunately, in the case of solids and liquids, 

 has not been accurately determined, so that this simple 

 measure cannot be applied; but since the specific heat of 

 liquids invariably exceeds that of their vapors at the same 

 temperature, and the liquid coefficient of expansion is less, 

 the cohesion in the liquid state must be much greater 

 than in the state of vapor; and we may roughly calcu- 

 late, in certain cases, the law of its variation. 



We have, for instance, for boiling water, a specific 

 heat of 42,000,000 ergs (C. G. S.), while that of steam, 

 under constant volume, is 15,600,000 ergs, nearly; the 

 difference being 26,400,000, and the coefficient of volumi- 

 nal expansion of water at 100° being (apparently) .0007, 

 a force of 38,000,000,000 dynes (C. G. S.) must be 

 overcome in order to account for this work. The pres- 

 sure of saturated steam is less than its calculated value, 



