Diffusion controlled autocatalytic growth of revert periodic precipitation of cadmium sulphide in lyophillic colloid

The experimental conditions for revert and direct periodic precipitation of cadmium sulphide in lyophillic colloid have been investigated. The theoretically derived Mathur’s spacing law, which suits both revert and direct types of precipitation has been experimentally verified. An attempt has been made to explain the formation of revert cadmium sulphide bands by considering preferential adsorption of sulphide ion, interpenetrating distribution of ions, and autocatalytic growth of cadmium sulphide particles within the electrical double layer. The flocculation is explained as being due to the specific adsorption of the hydrolyzed counter ion. The increase and decrease in the value of velocity constant is explained on the basis of the formation of autocomplex species.

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