An Apparatus for Precisely Measureing the Surface Tension of Ultra-Pure Water

The thermodynamic properties of water are likely the most studied of any liquid. In particular, this is true for its surface tension, where there exists a number of techniques to measure it under and number of different conditions (different gases, temperatures, etc.). But none of these prior measurements were undertaken with truly clean water as they were measured in some kind of gaseous atmosphere and in a majority of the cases, with normal air. This leads to contamination of the water through particles in the air and gases that make up the atmosphere itself. The exact influence of these contaminationson surface tension measurements is still not fully known. For this reason, the goal of this master’s thesis was to create a drop of water as clean as possible in its own pure-water vapor and to measure the surface tension of this clean water drop with pendant drop tensiometry. In this way, surface tension measurements can be achieved free of the influence of contaminants and other gas phase species. This goal was achieved in part; the instrument was successfully built and initial surface tension measurements of the first water drops in their pure-vapour were undertaken. This thesis will discuss the instrument design and construction as well as the initial surface tension measurements.