Tomokazu Asano

Study on the Precise Measurement of the Surface Tension of Liquids

This study is intended to be a contribution to the precise measurement of the surface tension of liquids, especially of molten metals. We propose a new method for calculating the surface tension from the photograph of the pendant drop. We deal with the case in which the pendant drop has an axis of symetry. Notations : p0=the pressure difference at the apex between in- and outside of the surface. ρ=the difference of density between the drop and its surrounding. σ=the surface tension of the liquid. g=the accelaration due to gravity. A=a constant for the case (=p0/gp). B=the capillary constant of the liquid (=2σ/gp). Introducing two parameters X=sin θ/r and Y=z-(1/r2) ∫z0 r2dz, we have the relation Y=A-B X which indicates a straight line. From this we can compute the capillary constant B by the method of least square, using the values of X and Y obtained experimentally at many points on the meridian. As regards the accuracy of the method, we find that, through repeated experiments on distilled water, the range of errors is 0.5%. Such an accurate result can not be obtained by other drop shape methods.