AbstractRheoelectrolysis is defined as convection‐free electrolysis of an electrolytic solution under simultaneous liquid transport from anolyte to catholyte andvice versa. Equal rate of transfer in both directions is assumed in this paper, and hence there is no liquid flow within the electrolyser. If this process is conducted long enough, a steady state can be expected, characterised by mutually balancing flows of ion constituents within the electrolyser (by electric migration) and in external ducts (by pumps). The differential equation of the steady state is deduced, and it is shown that it is easily solvable if transport numbers and diffusion coefficients are constant throughout the electrolyser. In this case the concentration courses become linear. The conditions for the presence of both buffer components in all parts of the electrolyser. are given. These conditions being satisfied, it is possible to calculate the pH course to be expected throug the eleltolyer. It is found that a pH span of about 2.6 unite can be covered by the rheoelectolysis of an odinary buffer solution. The pH gradient is at a minimum at the centre of the apparatus and increases towards both electrodes. The pH courses is sigmoid in shape and appears to be very useful for isoelectric focusing of proteins and other ampholytes. The method may become important in preparative work on a large scale in order to save the cost of carrier ampholytes in quantitie