On the Use of Washburn's Equation in the Analysis of Weight-Time Measurements Obtained from Imbibition Experiments.

A careful analysis of the experimental results from imbibition experiments, expressed as the increased weight of a porous layer once it was in contact with a liquid, vs time, has been done on the basis of Washburn's equation, which is usually the main tool for that analysis. It has been found that the experimental results reflect other physical phenomena more than imbibition, among them the effect of the initial contact between plate and liquid and the evaporation of liquid from the wetted porous layer. The unavoidable disturbance introduced by the first of these phenomena leads to the need for rescaling of the experimental data. Once this is done, Washburn's equation has to be applied accordingly to the new reference system chosen. Also, it has been shown that if evaporation is present, experimental data deviate from Washburn's predictions. This effect disappears if the porous layer is covered. Copyright 1999 Academic Press.