Theoretical and experimental analysis of the diaphragm diffusion method for study of the state of trace elements in aqueous
solutions is presented. It is shown that the method has substantial advantages over other diffusion methods and over conventional
use of dialysis, particularly when nucleopore or other membranes with small internal surface area are employed. These advantages
include rather short experimental time, not exceeding tens of minutes, lower adsorption losses and lower shift of equilibria
among various forms of the trace element studied. A new method for the continuous measurement of and for the evaluation of
diffusion is suggested, which enables calculation of the abundance of colloidal forms of the element. Verification of the
method is carried out for a particular case using trace radiocerium.