Pressure Argument for the Capillary Rise

The pressure at point B (located at height z = 0) is Pq. The pressure difference between A and B is purely hydrostatic, point B bearing the weight of a liquid column of height H. Expressing the equilibrium of pressures gives 

The law of capillary rise (2.31) flows directly from equation (2.33). 

FIGURE 2.18. The hydrostatic pressure drop between points B and A offsets the Laplace underpressure at point A. 

Finally, the fluid column resulting from capillary rise can be described in terms of the forces at equilibrium. There exists a force F that supports the weight of the column, which can be expressed as 

The length of the contact line is 27tR. The capillary force / per unit length supporting the fluid column is given by 

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