Abstract: The invention relates to a method for the measurement of the movement of colloidal particles in suspensions or solutions. The apparatus used in this method comprises an electrophoresis tank equipped with two electrodes between which an electrical field can be applied.A beam of radiation produced at the outside of the tank having a thickness of not more than 1000.mu. as viewed in the direction of the lines of force of the electrical field set up between the electrodes is directed so as to skim the electrode away from which the particles move under the effect of the electrical field.In order to determine the mobility of the particles the optical density of the liquid is measured a first time without applying the electrical field, and a second time after having applied the field during not more than 10 seconds.

Abstract: The invention relates to an improved method and apparatus for the measurement of the movement of colloidal particles in suspensions or solutions, wherein an electrophoresis tank is equipped with two electrodes and a filtering membrane positioned substantially parallel and equidistant to the electrodes.A flat beam of radiation produced at the outside of the tank having a thickness of not more than 1000 .mu. as viewed in the direction of the lines of force of the electrical field set up between the electrodes is directed so as to skim the side of the membrane from which the particles move under the effect of the electric field.With this improved arrangement the influence of secondary interfering phenomena appearing essentially when measuring the movement of colloidal particles in highly mineralized waste waters, can be eliminated.