Negative Pressure in Capillary Liquid

Bulk liquid at negative absolute pressure is superheated, which is a metastable state. It is a metastable state because the S3d em can move to a state of lower free energy by creating cavities filled by vapor however, to create a cavity (vapor bubble) an energy barrier has to be overcome. If the liquid is at a pressure p, then the work required to create a bubble of volume V and surface area A, filled with vapor at a pressure pv, is given by  

Assume in Fig. 11.2 that we have a thin rectangular capillary (height h width). Neglecting the meniscus curvature in the lateral plane, the pressure of the liquid phase piiq is given by  

Together with the known stiffness of the channel cover it was possible to estimate the negative pressure of the liquid to be, depending on the method to analyze the meniscus shape, —17 10 bar or —14 8 bar. Within the limits of the measurement accuracy this is in accordance with Eq. 11.3 (—12 bar). 

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