Abstract: Tween 80 and propyl gallate were found to form an oily product. Within the range of concentrations used in this experiment, the amount of the oily product formed varied with the relative concentrations of Tween 80 and propyl gallate.Ultra violet spectroscopy determintion of the oily product in Tween 80 solution showed that the λ_max was shifted to longer wavelength. This seemed to indicate that the oily product was a complex of Tween 80 and propyl gallate.The incorporation of propyl gallate into Tween 80 solution was found to cause a lowering in surface tension.