Rideal-Washbum equation

The rate of liquid penetration has been investigated by Rideal and Washburn [7, 8]. For horizontal capillaries (gravity-neglected), the depth of penetration I in time t is given by the Rideal-Washbum equation [7, 8] ... 

The rate of penetration of a liquid by a distance I through capillaries with radius r has been described by the Rideal-Washbum equation,... 

The Rideal-Washbum equation can be applied to obtain the contact angle of liquids (and surfactant solutions) in powder beds. K should first be obtained using a liquid that produces zero contact angle. This is discussed below. 

Another important factor in the wetting process is the role of penetration of the liquid into the charmels between and inside the agglomerates. This has to be as fast as possible to aid the dispersion process. Penetration of liquids into powders can be qualitatively treated by the Rideal-Washbum equation [74], assuming the powder to be represented by a bundle of capillaries. For horizontal capillaries (where gravity may be neglected), the rate of penetration of a liquid into an air-filled tube is given by... 

The imbibition rate, q, of a SLM can be correlated with the thickness of the solid support by the Rideal-Washbum equation (57) ... 

Thus, a plot of f- versus t gives a straight line, from the slope of which 0 can be obtained. The Rideal-Washbum [7, 8] equation can be appUed to obtain the... 

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