The first part of this paper deals with a method for the accurate determination of the surface tension of liquids available in volumes of not more than one or two cubic millimetres. The method described does not involve any knowledge of the density of the liquid. The second part of the paper describes a series of measurements of the variation with concentration of the surface tension of aqueous solutions of p-toluidine. Here, also, the method employed is independent of a knowledge of the density of the solution.