AN APPARATUS FOR MACROSCOPIC CATAPHORESIS 

 EXPERIMENTS. 



By JOHN H. NORTHROP and GLENN E. CULLEN. 



{From the Laboratories of The Rockefeller Institute for Medical Research.) 



(Received for publication, May 10, 1922.) 



The form of apparatus^ shown in Fig. 1 has been found very con- 

 venient 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 clamped in a vertical 

 position, and the apparatus is filled with saturated zinc sulfate. The 

 three-way stop-cocks are then closed 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 m sucrose solution con- 

 taining 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 ad- 

 justed carefully by means of the stop-cocks so that the line of demarca- 

 tion is opposite one of the graduations on the side arms. The upper 

 stop-cock is then closed 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 con- 

 venient interval. 



'For a discussion of this and similar methods see Burton, E. F., The phys- 

 ical properties of colloidal solutions, London, New York, Bombay, Calcutta, and 

 Madras, 2nd edition, 1921. 



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