These are reasonable assumptions with low viscosity fluids suspended in high viscosity fluids which are subjected to low rates of shear. Just as the pressure exerted by surface tension in a spherical drop is ** f and the pressure exerted by surface tension on a cylindrical shape is ** f, the pressure exerted by any curved surface is ** f, where |g is the interfacial tension and ** f and ** f are the two radii of curvature. This formula is given by Rumscheidt and Mason. If a is the major axis of an ellipsoid and b and c are the other two axes, the radius of curvature in the ab plane at the end of the axis is ** f, and the difference in pressure along the a and b axes is ** f.

There are no data published in the literature on the shape of low viscosity drops to confirm the above formulas. However, there are photographs of suspended drops of cyclohexanol phthalate (viscosity 155 poises) suspended in corn syrup of 71 poises in a paper by Mason and Bartok. This viscosity of the material in the drops is, of course, not negligible. Measurements on the photograph in this paper give ** f at the maximum rate of shear of ** f. If it is assumed that the formula given by Lodge of ** f, cosec 2lc applies, the pressure difference along the major axes can be calculated from the angle of inclination of the major axis, and from this the interfacial tension can be calculated. Its value was ** f from the above data. This appears to be high, as would be expected from the appreciable viscosity of the material in the drops.