[ 1'^ J 



No. 2. 



CATAPHORESIS OF AIR-BUBBLES IN VARIOUS LIQUIDS. 



By THOMAS A. McLAUGHLIN, M.Sc, A.Inst.P., 

 University College, Galway. 



[Read April 25. Printed June 1, 1922.] 



On the subject of the electrification in colloids, that is, of fine particles in 

 suspension in a liquid medium, much research has been done and a fair imder- 

 standing obtained. Likewise, something has been done on the electrification in 

 emulsions, but a broad field for research remains in this case of liquid suspensions 

 in liquid. In the remaining case, of what, for the sake of continuity, may be 

 termed gas suspensions in liquids, still less has been done, and, in view of the 

 advanced state of knowledge on electric phenomena in gases, this seemed a promising 

 field for research on cataphoresis phenomena. 



Mention is made by Quincke' of the motion of air-bubbles under an electric 

 field. He reports that air-bubbles in water, carbon disulphide, and turpentine 

 move under an electric field, in water towards the positive pole, in carbon disulphide 

 and turpentine towards the negative pole. McTaggart^ verifies Quincke on air- 

 bubbles in distilled water, and finds no motion of air-bubbles under an electric 

 field in the pure alcohols, methyl, ethyl, propyl, and isobutyl. Otherwise, there 

 seems to be no record of tlie motion of air-bubbles in pure liquids under an electric 

 field. In the present research the plan was to make preliminary investigations 

 into the charge on air-bubbles in i^ure liquids, with special reference to badly con- 

 ducting liquids. It was thought possible, at first, that the investigation might be 

 approached after the manner of Millikan's oil-drop experiments, that is, that the 

 upward tendency of an air-bubble in a liquid might be balanced, owing to the 

 charge on the bubble, by an electric field, and from such balancing experiments the 

 charge calculated. It was decided, however, to proceed with preliminary investiga- 

 tions with apparatus of McTaggart's type, and, with a fuller knowledge of the 

 phenomena, to return to the problem by other methods of investigation. 



The apparatus used was a glass tube 18 mm. diameter and 5 cm. long, fitted 

 with ground brass plugs, which Were air-tight. On one plug a pulley was cut, and 

 both were supported between pivotal ends on a heavy base, fitted with levelling 

 screws. The tube was rotated, as in McTaggart's experiments, by a Rayleigh 

 motor. Tlie motor and the apparatus stand were clamped in position, so that 

 every tiling was steady, and regular motion of the tube was obtained. The required 

 air-bubble was simply introduced by removing one plug of the tube, pouring in 

 liquid, and reintroducing the plug in time to catch a bubble which had been formed 

 by the pouring of the liquid. The tube being in position and rotating, the bubble 

 took up a position on the axis of the tube, and could be kept thus at rest during 

 the period of observation by proper adjustment of the levelling screws and speed 

 of the motor. The bubbles were illuminated by an electric lamp through a narrow 



' "Pogg Ann." 113, 1861. = Phil. Mag., 27, p. 297, and 28, p. 3C7, 1914. 



SOIENT. PROC. K.D.S., VOL, XVII, NO. 2. D 



