An Interfacial Tensiometer for Universal Use

The important and fundamental works of Quincke, Hardy, McC. Lewis, Morgan, and lately Harkins and his collaborators have thrown much light on the behavior of liquids at interfaces, and it may seem hardly necessary to develop a new method in order to study this phenomenon, as those existing have reached a high degree of accuracy. However, if the values of the interfacial tensions of pure liquids have been well established by these investigators and others, the changes of the interfacial tension due to adsorption in function of t ime--a phenomenon similar to that first studied in our laboratoryl--have not, to our knowledge, been studied so far, for lack of proper technique. Consequently, considering the number of new phenomena which were brought to light by the use of the tensiometer first described in this Journal 6 years ago 2 we thought it might be of interest to devise a similar instrument with which measurements of interracial tension could be made in a few seconds, conveniently, in any laboratory, to 0.1 dyne. Our first idea was to utilize the tensiometer as it actually exists on the market, with perhaps a slight modification of the platinum ring. However, as the ring can only be pulled upwards, it limits the measurements for water interfaces, to liquids floating on water; i.e., having a specific gravity < 1. In order to render the instrument universal, it was decided to fix the ring to a rigid support, so that it could be pressed down by means of the torsion wire, as well as pulled