In this work, diffusion data were collected using a CSFR technique, which typically involves perturbing the inlet concentration to a flowthrough system in a sinusoidal manner and monitoring the amplitude of the concentration in the effluent. The procedure is repeated at various frequencies, and several individual experiments are required to produce one diffusion data point. As noted previously, the advantage of the method is its sensitivity to the rate-controlling mechanism, as the shape of the response curve depends on the mechanism. However, because experiments are conducted over a large frequency range (typically about 0.0001 Hz -1 Hz), significant experimental time is required, particularly at the lower frequencies.