Experiments with rotating liquid films

Abstract

Plateau, in his great work ‘Statique des Liquides,’ has given a very short description of an experiment by Eisenlohr, who enclosed in a vacuous globe of glass some soap solution. On manipulating the globe he obtained films crossing the globe, and on rotating the globe he obtained coloured rings in the film. So far as I can understand the very short description, the position of the film must have been a matter of chance, and consequently the curvature, so that to obtain a plane film by this method would have been a matter of chance, and obviously it would have been impossible to manipulate with the film itself. Not knowing of this experiment, I desired last year to make some experiments with rotating films, and designed and constructed for the purpose the apparatus I am about to describe, and the phenomena obtained are so interesting and beautiful that I wish to present to the Royal Society a short but sufficient account of them. I intend to make a more detailed explanation in the form of an additional chapter to my book on ‘Soap Bubbles’ (published by the Society for Promoting Christian Knowledge). I have made up the apparatus in many forms and sizes, but for observing the phenomena I have found that to be described the most suitable. A cheaper form is being made and will shortly be available for general use. Referring to the figure, which is a vertical section, a box of circular cross-section is mounted upon a tubular support into which a steel ball has been forced. The whole runs on a steel upright fixed in a heavy tripod with three levelling screws. A number of pulley grooves make it possible to turn the box at very different speeds by means of a string driven by a small motor, but the most convenient method of driving for ordinary observation is by rolling the hand or fingers over the tubular support, which is roughened to increase the friction. A transparent conical cover of thin celluloid fits easily over the box. A central binding screw made of brass is secured to the celluloid, and through the centre of this there is a small hole fitted with a conical stopper which can be removed or replaced while the box is spinning. The inturned rim is drilled with a number of holes, so that when a film is stretched on the feather edge of the rim there is free air communication between the air in the two spaces above and below the film; this is essential where it is desired to maintain the plane form of the film. When the film is curved the brilliance and beauty of the phenomena are not so marked. The interior of the box is dead black. The diameter of the film in the apparatus now described is 4 inches (10 cm.), but I have made them both much larger and much smaller.