Dynamic interfacial tension in hexadecane water systems containing ready-made and in-situ-formed surfactants

Dynamic interfacial tension (IFT) between two immiscible liquids has been i nvestigated by the method of drop volume tensiometry. Hexadecane and water were employed for the measurements. In the case of the pure oil-water syste m, it was found that with hexadecane as the drop phase the IFT was very clo se to the published value (53.5 mN/m). When water acted as the drop phase t he apparent IFT was about 20% higher, and a correction method was developed to account for the different geometry of droplet formation. A similar effe ct was observed when a surface active additive was present in either one or both phases. The effects of ready-made surfactants and their in-situ-forme d equivalents were examined. It was found that both decreased the IFT betwe en the two phases, but the in-situ-formed surfactant was more effective in that respect. It was also found that the IFT between acidic hexadecane and NaOH solution increased when ready-made surfactant was added to the alkalin e solution. Addition of salt (NaCl) produced the expected decrease in IFT w hile the effect of added NaOH appeared to be more complex.