Based on a theory of sessile drop in gravity, a method to evaluate surface tension is proposed, and its applicability is discussed. All of parameters are theoretically normalized. Although it is impossible to obtain analytic solution of the surface profile of the sessile drop, it is possible in an extreme condition of large volume. A universal parameter which determine the volume of liquid is derived in a normalized form. The large volume condition is theoretically defined using the parameter. Under the large volume approximation, an equation is derived which gives the surface tension from a height and an angle of the drop surface. In order to discuss applicability of the approximation, numerical calculation is carried out. It is found that the surface tension can be obtained with a tolerance less than 16%, if we measure the height of the sessile drop and the contact angle, under the large volume approximation. This method proposed in the present study is beneficial for the estimation of wettability of liquid using sessile drop.
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