An Apparatus for Macroscopic Cataphoresis Experiments

The form of apparatus 1 shown in Fig. 1 has been found very convenient for the determination of the migration of fine suspensions in the electric field. Its essential difference from the usual cataphoresis apparatus is that the whole is inverted so that the central portion, which contains the suspension which is to be studied, is above the heavier electrode solutions and may be left open. This increases both the convenience and accuracy of method since (1) a greater latitude in concentration of solution is allowed, (2) the boundaries may be adjusted more exactly, and (3) the solution may be renewed without disturbing the electrode solution. The zinc electrodes are put in place with rubber stoppers, the tube is damped in a vertical position, and the apparatus is filled with saturated zinc sulfate. The three-way stop-cocks are then dosed and the zinc sulfate in the upper part of the cell is washed out through the "tail holes." The tubes above the stop-cocks are now filled with 0.1 x~ sucrose solution containing the same concentration of electrolyte or other substance as is to be used with the suspension. The sugar solution is then allowed to run out until the level reaches the small tube connecting the funnel and the U-tube. The suspension is then added and the level adjusted carefully by means of the stop-cocks so that the line of demarcation is opposite one of the graduations on the side arms. The upper stop-cock is then dosed and the lower ones are opened so as to connect the zinc sulfate with the sugar solutions. The current is applied and the distance traversed by the boundary determined after a convenient interval.