Historical aspects of capillarity and capillary condensation

Abstract

The basic equation of capillarity is generally associated with the names of Thomas Young and Pierre Simon Laplace. Careful perusal of the early literature has revealed some unexpected historical aspects. For example, Young’s 1805 essay on the ‘cohesion of fluids’ was purely descriptive, but it did provide a basis for the ‘classical’ treatment of capillarity and wetting. In contrast, Laplace’s 1806 work involved a more ‘modern’ energetic approach to capillary attraction, but avoided any direct reference to surface tension. The related capillary condensation equation is now universally known as the Kelvin equation. However, this exponential relationship was not the form of the original equation proposed in 1871 by William Thomson (later Lord Kelvin). Zsigmondy (1911) [11] applied Thomson’s original linear equation in his seminal study of silica gels. Although the Kelvin equation is still widely used for mesopore size analysis, its limitations began to be recognised in the 1930s.