Teorell’s membrane oscillator (Teorell 1959) consists of a silica gel wide pore membrane which separates two compartments containing the same electrolyte but with different concentrations. When a critical value of constant current flows through the membrane, oscillations of potential difference and pressure difference across the membrane are observed. Teorell described his membrane by assuming 1) charged membrane, 2) electroneutrality, 3) Fick’s diffusion equation with convection, 4) electroosmotic flow, 5) the concentration of oppositely charged mobile ions are taken to be equal at each point within the membrane, 6) Ohm’s Law and 7) a resistance relaxation equation $$ \frac{{dR}}{{dt}} = k(R - R{(V)_{steadyState}}) $$ where R is the resistance and V is the volume flow rate. The last relation is offered as an empirical one, which serves to describe the data quite well.