Refractive Index Effects in Pendant Drop Tensiometry

Abstract An optical model is established to investigate the effects of refractive index changes on measurement interfacial tension by pendant drop method with axisymmetric shape analysis. In such measurements, light passes from through a surrounding bulk phase, an window and air reach lens camera system. The relation between object image size typically determined calibration and, if indices any materials in path change measurement, correction should be made. simple derived this paper allows corrections calculated along corresponding contribution overall uncertainty tension. was verified measurements decane water under two different conditions. Neglect shown cause errors up 6 % when phase changed (during calibration) measurements) about 9 system calibrated without used for final measurements. refraction due high pressures supercritical fluid states can also lead errors. proposed facilitate more accurate reduce amount repetitive work required.