A very useful capillary apparatus is pioneered for the experimental measurement of liquid-liquid interfacial tension of two immiscible liquids, with highly accurate results. The method features integration of two coexisting capillary actions. The results of measurement for alkanes-water, heptanol-water and hexanoic acid-water systems (in the range of 298-333 K) demonstrate that this method of liquid-liquid interfacial tension measurement is highly accurate, as known to be the case for liquid-vapor system. The coexisting capillarity actions involving liquid-liquid system is studied by the capillary constant, and importantly is practiced to be the augmentation of the two neat liquid capillary constants less-a length scale proportional to the extent of effective dispersion interaction at the liquid-liquid interface. (C) 2014 Elsevier B.V. All rights reserved.