Capillary tube for measurement of surface tension at boundary between two immiscible fluids or air and fluid has tapered tip with internal tapering of bore

摘要

The capillary tube (1) is placed in a fluid. It has a parallel-sided bore (5) of given radius (r) with a short tapered tip region (2). Air or gas is blown into the capillary tube to blow a bubble (3) at the tip of the tube. The pressure (p) required to blow the bubble is measured and is plotted against time (t) to produce a curve (4) of a characteristic shape.