PATTERNING TRENDS AND CHAOTIC BEHAVIOR IN CO2+ NH4OH LIESEGANG SYSTEMS/

Co(OH)(2) Liesegang patterns from Co2+ and NH4OH in gelatin are studie d in thin glass tubes. The experiments are performed in the limit of l arge initial concentration difference (a) between the interdiffusing e lectrolytes. Patterning trends are investigated as the initial concent ration product sigma = [Co2+](0)[NH4OH](2)(0) is varied (we keep [NH4O H](0) constant and vary [Co2+](0) in the limit of large Delta). Time s eries of the total number of blinds in the pattern show a random distr ibution apparently indicating the chaotic character of that variable. When the bands are counted in the bottom portion of the pattern (the l ast 4 cm measured from the last band), their number (denoted nu therei n) decreases monotonically with time at all concentrations. The patter n thus regularizes itself in that region. The spacing between the band s is measured as a function of distance from the junction between the co-precipitate solutions, at different initial concentrations. The var iation of spacing with distance is found to fit a quadratic equation. The variation of spacing with concentration at a given location is als o studied and is found to involve an exponential term. Then a generali zed equation expressing the spacing as a function of concentration and distance is determined. A three-dimensional plot is constructed to re present the obtained variations. Our results are then compared with pr evious experimental findings and theoretical formulations of Liesegang preciptation phenomena.