This paper describes an instrument to measure the interfacial tension (IFT) of aqueous surfactant solutions and crude oil. The method involves injection of a drop of fluid (such as crude oil) into a second immiscible phase to determine the IFT between the two phases. The instrument is composed of an AT-class computer, optical cell, illumination, video camera and lens, video frame digitizer board, monitor, and software. The camera displays an image of the pendant drop on the monitor, which is then processed by the frame digitizer board and non-proprietary software to determine the IFT. Several binary and ternary phase systems were taken from the literature and used to measure the precision and accuracy of the instrument in determining IFTs.

The instrument has been used to determine the IFTs for several bacterial supernatants and unfractionated acid precipitates of microbial cultures containing biosurfactants against medium to heavy crude oils.

These experiments demonstrate that the use of automated video imaging of pendant drops is a simple and fast method to reliably determine interfacial tension between two immiscible liquid phases,- or between a gas and a liquid phase.

You can access this article if you purchase or spend a download.