In this paper, the effects of several factors such as surfactant concentration, solute concentration, impeller speed and holdup on the mean drop diameter ( ) during emulsification have been studied in a single-stage mixer-settler extractor. A video technique has been developed in order to measure drop size distribution in the mixing chamber using a digital camera. The results show decreases with an increase in solute concentration. decreases significantly in low concentrations of surfactant, while in general, droplet diameter decrease with surfactant concentration. Though it maybe negligible. Three correlations are derived: without solute and surfactant, with solute, and with surfactant. These correlations showed a good agreement with experimental data and Hinze-Kolmogorov theory has been well proved by all of them. The experimental results in the first case were compared with Godfrey’s model and it has a minor deviation from Godfrey’s model. For the second and the last case, there weren’t any models or experimental data to compare with. In fact, the last two cases were investigated for the first time.