The cat. speed of colloidal prussian blue (prepared by peptisation with oxalic acid) with the progress of dialysis first increases and then decreases, while the stability as determined by flocculation values with KC1 continuously decreases. The cat. speed on dilution first increases and then decreases in some case while it continuously decreases in others; the stability on dilution is found to decrease continuously in all the cases. These results of dialysis and dilution are exactly similar to those obtained with colloidal ferric and thorium hydroxide investigated by Desai and co-workers.
The changes in the cat. speed and viscosity under different conditions show that neither the view of Dhar nor of v. Smoluchowski can individually explain the results.
The idea of critical potential is supported.
The cat. speed of the sol decreases on ageing and exposure to sunlight, sols dialysed for short periods even coagulating when exposed to sunlight for a couple of minutes.