XX CONTENTS 



12. Commentary on Pages 215-219. Solids Which 

 Absorb Fluids. Elucidation of Some Mathe- 

 matical Operations 502 



L. The Influence of Surfaces of Discontinuity upon 

 THE Equilibrium of Heterogeneous Masses. 

 Theory of Capillarity (Gibbs I, pp. 219-331; 331- 



337), J. Rice 505 



I. Introductory Remarks 505 



1. The Surface of Discontinuity and the Dividing 



Surface 505 



2. The Mechanical Significance of the Quantity 



Denoted by <r 507 



II. Surface Tension 509 



3. Intrinsic Pressure and Cohesion in a Liquid 509 



4. Molecular Potential Energy in a Liquid 513 



5. An Alternative Method of Treatment 516 



III. The Quasi-Tensional Effects at a Curved Surface 518 



6. Modification of the Previous Analysis 518 



7. Interpretation of o- as a Tension 520 



IV. Statistical Considerations 523 



8. The Finite Size of Molecules 523 



9. Distribution of Molecules in Two Contiguous 



Phases 525 



V. The Dividing Surface 527 



10. Criterion for Locating the Surface of Tension .... 527 



11. An Amplification of Gibbs' Treatment 529 



VI. The Adsorption Equation 533 



12. Linear Functional Relations in Volume Phases. . . 533 



13. Linear Functional Relations in Surface Phases . . . 534 



14. Derivation of Gibbs' Adsorption Equation 535 



15. Variations and Differentials 537 



16. Condition for Experimental Tests 537 



17. Importance of the Functional Form of a in the 



Variables 538 



VII. Other Adsorption Equations 541 



18. The Exponential Adsorption Isotherm 542 



19. Approximate Form of Gibbs' Equation and Thom- 



son's Adsorption Isotherm 543 



20. The Empirical Laws of Milner and of Szyszkowski 



for <T and c. Langmuir's Adsorption Equation. 



Frenkel's Equation 551 



21. Energy of Adsorption 554 



VIII. Experimental Investigations to Test the Validity of 



Gibbs' Adsorption Equation 557 



22. The Earlier Experiments to Test Gibbs' Equation. 557 



