Motion of a liquid through a narrow space due to surface tension and contact with the walls; it draws the chromatographic mobile phase through a thin-layer chromatography coating.
Two wide vertical plates separated by gap provide two contact lines per unit width. Upward surface-tension force balances column weight . Compared with a circular tube of radius , the height ratio is for the same fluid and contact angle. Equal plate gap and tube diameter give half the tube rise.
For a circular capillary of inner radius , balance the vertical force against the hydrostatic column weight . The displayed signed height follows, neglecting meniscus-volume corrections. A wetting liquid with rises, whereas a nonwetting liquid with is depressed. The contact angle is measured through the liquid. The expression uses radius rather than diameter and presumes equilibrium at the specified wall chemistry.
A negative signed capillary rise for a nonwetting liquid: the equilibrium contact angle exceeds a right angle, giving in Jurin's law. Correcting a mercury-column measurement requires a consistent meniscus and surface condition.
For unchanged fluid, gravity and capillary geometry, equilibrium rise is proportional to the cosine of the contact angle measured through the liquid. Changing from angle to complete wetting therefore multiplies the height by . If contamination also changes liquid surface tension or density, the contact-angle ratio alone does not fix the new height.
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Capillary action, also known as capillarity, is a phenomenon that occurs when liquid rises or falls in a narrow space, such as a thin tube or porous material, due to the combined effects of cohesion and adhesion. **Key aspects of capillary action include:** 1. **Cohesion**: This is the attraction between molecules of the same substance. In the case of water, hydrogen bonds cause water molecules to be attracted to each other.