In situ force-balance tensiometry

Although a fundamental physical parameter, surface tension is difficult to measure. Common tensiometry inaccuracy comes from failure to control air-li quid-solid contact conditions, or account for liquid meniscus geometry and buoyancy corrections. This paper describes an in situ tensiometry technique , based on withdrawal of a thin-walled tube from the liquid interface, that enforces a known air-liquid-solid contact condition. This technique can be pursued at any level of experimental hygiene. Experimental results for fil tered tap water, an alcohol-water solution, and a surfactant-water solution show that results repeatable to three significant digits are obtained with modest effort for a variety of geometrical parameters.