Ring morphology and pH effects in 2D and 1D Co(OH)2 Liesegang systems.

We study the factors that affect the morphology of Co(OH)(2) Liesegang rings, in a way to obtain concentric rings with large spacing, upon an appropriate variation in the experimental conditions. Such well-resolved patterns are obtained under optimum conditions: decrease in the concentration of the outer electrolyte, increase in the concentration of both the inner electrolyte and the gelatin in the hosting gel medium, and increase in the strength of a constant radial electric field applied across the pattern domain. The effect of pH on the bands in a 1D Co(OH)(2) Liesegang pattern is also investigated. The initial pH of the diffusing solution plays a central role in altering the band morphology, because the outer electrolyte (NH(4)OH) is a base, strongly affected by the H(+) equilibrium. The number of bands decreases and the interband spacing increases with decreasing pH of the NH(4)OH solution. The pattern morphology in that case is controlled by the NH(4)Cl/NH(4)OH ratio.