VII. On the thickness and electrical resistance of thin liquid films

Abstract

In a paper on the “Limiting Thickness of Liquid Films,” presented to the Royal Society in 1883, we proved that in the case of a large number of films the mean thickness of that part which was thin enough to display the black of the first order of Newton’s rings was 11·6 μ. μ. (micromillimetres). The validity of the methods employed was assured by the agreement between the results obtained. The mean thickness of a number of black films was measured optically by a method which involved the assumption that the refractive index of the substance of the film was the same as that of a large mass of the same liquid. The thickness of black films was also determined by measuring their electrical resistances, and assuming that the specific resistance was the same as that of the liquid in mass. The means of the results obtained by the two methods were 11·8 μ. μ. and 11·3 μ. μ. respectively, which were sufficiently in accord to justify the assumptions.