Menisci formed by a cone at a free liquid surface. An absolute method of surface tension measurement

Abstract

A method is described by which the surface tension of a liquid may be measured from the maximum force exerted by a meniscus formed between a cone and the free surface of a liquid. The maximum force on the cone depends on the angle of the cone, the angle of contact of the liquid with the surface of the cone and on the capillary constant of the system.

For a given cone angle this maximum force has been derived theoretically by numerical analysis of Laplace's capillary equation. Assuming a contact angle of zero, the maximum force (expressed in dimensionless units) has been determined with six figure accuracy for cone angles of 1 to 75°.

The maximum force has also been measured using a conventional balance with the cone held at the surface of liquids contained in a temperature controlled vessel.

From a knowledge of the theoretical maximum force (the cone constant), the density of the liquid, the local gravitational acceleration and the measured force, the surface tension is determined.

The surface tensions of a number of liquids have been measured. The temperature variation of the surface tensions of both benzene and water have also been obtained.

The absolute accuracy of the method is discussed and data are compared with literature values.