A STUDY OF NOISE GENERATED DURING ION TRANSPORT ACROSS MEMBRANES

The noise spectra associated with the transport process through a membrane were measured. Relaxation times apparently attributable to ion pairing in the membrane were observed in some cases. Where discrete relaxation times did not dominate, the slope of power vs. the logarithm of frequency varied from an ω-1/2 dependence (particularly with anion membranes) to an ω-3/2 dependence. An ω-3/2 dependence is characteristic of diffusion noise and an ω-1/2 dependence can arise from concentration fluctuations across a layer of high resistance and small thickness. The bulk of the measured slopes fall between these two extremes and probably reflect various distributions of relaxation times.