The interfacial tension between demixed liquids has a large impact on the mass transfer over the phase boundary. In this paper a special version of the density-gradient theory for ternary systems, where the grand thermodynamic potential is calculated using the Koningsveld–Kleintjens model, is suggested. This approach allows the prediction of the interfacial tensions of practical important ternary systems based on information of the binary subsystems. In order to verify this idea two ternary systems showing only one miscibility gap, namely water + butan-1-ol + ethanol and water + acetone + toluene, were selected. The predicted interfacial tensions were very close to the experimental data taken from the literature and to own experimental data obtained by spinning drop measurements. Both systems differ in the enrichment behavior. Whereas ethanol will be enriched in the interface to a small amount, the enrichment of acetone is much more pronounced.

A quantitative x-ray fluorescence (XRF) analytical system has been developed with the emphasis on small sample size. The system employs a two kilowatt tungsten anode x-ray tube, and an 80 mm2 lithium drifted silicon x-ray detector arranged in a compact geometry. Operation at 55 kV and 20 m A give a sensitivity of 153 counts/min/ng at Z=42 (molybdenum). A computer controlled target changer makes it capable of analyzing 32 targets automatically. The sample target is rotated during irradiation, so that the average sample position is defined to 0.2 mm. Several sets of 5 to 9 calibration targets have exhibited a standard deviation of less than 1%.

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