R. Sultan et S. Sadek, PATTERNING TRENDS AND CHAOTIC BEHAVIOR IN CO2+ NH4OH LIESEGANG SYSTEMS/, Journal of physical chemistry, 100(42), 1996, pp. 16912-16920
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.