methods for the determination of both surface and interfacial A method of profile optimization for determining the surface tension of liquid-fluid systems and may be the only choice and interfacial tension (IFT) of liquid-fluid systems from the for the IFT measurement of viscous liquids such as polyprofile of a pendant drop is described. A new, versatile routine for meric melts. This method is also suitable for measuring IFT estimating the drop shape parameter is introduced. The factors values under critical conditions such as under high pressures that affect the available accuracy of the method have been anaand/or at elevated temperatures. For measuring IFT behavior lyzed using theoretical simulations. It was found that the tilt of of liquid crystals (LCs), in which we are especially interthe drop profiles may lead to large errors in the resultant IFT ested (3), this method may be the most preferable due to values if the tilt was not corrected before or during the optimizaits very small contact interface between the solid substrate tion procedure. This effect could be reduced drastically if a profile (in this case the tip cross section of the needle used) and were averaged between its two sides and the mean profile were used for optimization. The aspect ratio of a drop image (or profile) the measuring liquid. In order to rule out the possible effect can be determined reliably by considering it one of the parameters of the solid substrate on the orientation of the LC molecules to be optimized. The dependence of the error in the resultant IFT in the surface layer and consequently on the IFT value of value on the error in the aspect ratio was found to be highly the LCs, it is beneficial to keep this contact interface as sensitive to drop shape. The available accuracy of IFT determinasmall as possible. In spite of these advantages this method tion using this method depends strongly on the precision of the has never become as popular as other classic methods such determination of the drop profiles. After error analysis using theoas the Wilhelmy plate method, the Du Nou ¨y ring method, retical simulations a 95% confidence interval of ca. 0.05 and 0.12% or the drop volume (or weight) method. The main reasons was estimated for this method for the profiles determined with for this unpopularity are the tedious work involved in the maximum statistical error of 3.5 and 7.0 mm, respectively. ᭧ 1996 later calculation and the limited accuracy available by using Academic Press, Inc.