Application of the Drop Weight Method to the Determination of the Surface Tension of Colloidal Solutions

Abstract

IN connexion with some work by Henry N. Harkins and myself on the surface tension of certain colloidal solutions, it seemed essential to hold the drop used for the determination at almost full extension any desired length of time before it was allowed to fall. As usual, the drop was allowed to fall from a tip of horizontal circular cross-section into a stoppered weighing bottle (method of J. L. R. Morgan). The weighing bottle was immersed in a thermostat, and was kept dry on the outside by an enclosure of glass and brass, such as was used by Harkins and Brown. This is shown diagrammatically in Fig. 1. The new modification consisted in supporting the supply bottle entirely by the rod A, which was supported in turn by a microscope stand upheld by a heavy tripod which rested on a pier outside the thermostat. The rod was made so small that there was no contact with the inside of the tube C′. There should also be no contact between the stopper of the bottle E and the inverted capillary U tube upon which the tip D is ground, since the adjustment of the level of the bottle E must transmit no vibrations to the hanging drop.