Abstract: A method for measuring the surface tension---Contour Curve Fitting Method, which is determined by digital video image processing of a sessile drop with using computer
was discussed. The image of a sessile drop of Li₂B₄O₇+KNbO₃ formed on a BN plate was recorded on a digital video tape and converted into digital data
of profile by using the technique of digital image acquisition and processing. The Segmented drop image was fitted with numerical solution of theoretical equations
to determine a surface tension. The thermal and solute surface tension coefficients were given by the following forms respectively, γ_T(mN/m)=210+0.15(T--900℃),
900℃≤ T≤1000℃ and γ_C(mN/m)=229--0.45(C_KN--10wt%), 10wt%≤ C_KN≤30wt%.

Key words: surface tension, sessile drop, contour curve fitting method, Li₂B₄O₇·KNbO₃ solution