On progress in forces since the DLVO theory

Abstract

The simplicity, consistency and an understanding of the limitations of the original DLVO theory has been lost. Where the theory apparently fails, new words to describe `non-DLVO' forces have been invented. `Extra-DLVO' forces, words like hydration, structural, oscillatory, hydrophobic, depletion, fluctuation, protrusion forces infest the literature. Some are real enough but some have the status of phlogiston. All predictability has disappeared in a confused proliferation of parameters. The original theory does not account for specific ion effects embraced by the term Hofmeister series. Nor did it pretend to. There is a fundamental inconsistency even at the continuum level in treating double layers via a nonlinear theory, and van der Waals-Casimir-Lifschitz forces by a linear theory. Further no theories have considered the effects of dissolved gas which are extremely important. An account will be given of the present situation in colloidal interactions, and how to resolve it. Show more