Based on the shape and size of a formed drop of fluid introduced into another fluid (provided the two fluids are immiscible), many parameters such as Interfacial tension (IFT) are determined. In addition, investigation of the effect of a particular parameter on the IFT can be achieved by measuring the change in IFT with the variation in the parameter.

Interfacial tension, capillary forces, and wettability are the factors affecting the shape of the drop of a lighter fluid through the tip of the apparatus of the pendant drop method into a heavier fluid. Before introduced to the cell, the two phases were distinct and the contact line separating the two phases was thin and clear indicating an immiscible mixture. At constant pressure, the temperature was incrementally increased in the two-phase fluid system, and the shape of the forming pendant drop is observed and captured by a camera.

With many attempts made to form the pendant drop, the drop was never formed at specific degrees of temperature. Although the fluids had come into complete equilibrium in the laboratory before introduced to the pendant drop cell, an unusual behaviour of the two fluids has been observed. The forming and un- forming of the drop as temperature was increased has not been consistent. The two phases at some temperatures were behaving as if they were somewhat miscible. Captured pictures of the behaviour of the fluids are shown and an attempt to explain the reasons of the unusual behaviour is presented in this paper.

The unusual behaviour suggests that the IFT – temperature relationship is a complex phenomenon and confirms some inconsistencies reported in the literature. Possible reason for the strange behaviour is that although the pendant drop method is a well-established technique for measurement of the interfacial tension (IFT), it may not be applicable for all IFT measurements conditions and/or the composition of the fluids used in the system.

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