Leidenfrost' Phenomenon

Abstract

A FEW days ago I was examining the “rosette” formed by a spheroid of water in a hot platinum capsule, and noticed that the outline was not a continuous curve, as is generally represented in books, but was “beaded” with re-entering angles as shown by the continuous, lines in figures 3, 6, 9, while the curve of each bead could be distinctly traced within the drop, forming a “fluted” outline, shown by the dotted lines in the same figures. It was at once manifest that both the “beaded” and “fluted” figures were produced by the superposition of the retinal images of the drop in two extreme conditions of vibration; that, in the case represented by 3, the drop was really vibrating like a bell which is sounding its first harmonic above its fundamental note, and therefore possesses six ventral segments, the extreme forms assumed being represented 1 and 2 respectively, and that 6 and 9 represent the appearance of the drop when vibrating like a bell which is sounding its second and third harmonic respectively. To verify this a spheroid of about five-eighths of an inch in diameter was produced; and as soon as the beaded decagon, 9, was steadily maintained, the room was darkened, and the spheroid illuminated by sparks from Holtz's machine. Immediately the curvilinear pentagons 7 and 8 were apparent, and frequently the vibrations continued perfectly steady for several seconds. When the drop had diminished in size the mode of vibration changed, and the crosses represented by 4 and 5 appeared when the sparks passed; on opening the shutters the beaded octagon 6 appeared almost perfectly steady in the capsule. The figures 1, 2, and 3 were obtained in the same manner, and with a larger spheroid twelve and sixteen beads were obtained, presenting respectively curvilinear hexagons and octagons when illuminated by the sparks. In one case a small spheroid presented a very large number of beads in its outline; but on examining it with sparks it was found to be produced by the crosses 4 and 5 rotating very rapidly about a vertical axis. Two or three particles of carbon introduced into a spheroid remained for a long time close to the surface of one “ventral segment”, like lycopodium powder on a Chladni's plate, and when they escaped from it were ensnared by the next segment. The figures observed when the spheroids were illuminated by sparks were fully as exorbitant as those shown at 1; 2, 4, 5, 7, and 8.