This paper presents a study of some features and characteristics of the Co2
+/NH4OH Liesegang system. The pattern of parallel Co(OH)(2) bands displays
peculiar properties that are unique among other Liesegang systems. First, t
he process of dissolution of bands at the top of the pattern coupled to, th
e formation of new ones at the bottom results in a propagating pattern that
moves down the tube. Second, the total number of bands N varies erraticall
y with time, unlike other Liesegang systems in which N increases monotonica
lly with time. These random oscillations in the variable N are related to t
he dissolution/precipitation scenario. New experiments are designed to obta
in a rigorous measurement of the total number of bands. Image analysis soft
ware (SigmaScan) is used to accurately determine N and the distance of:the:
first band from the junction between the two solutions, based on a cutoff z
ero absorbance criterion. A time series for N is obtained by monitoring the
pattern for 40 consecutive days. This time series is then analyzed numeric
ally using a "Chaos Data Analyzer" software. All the characterization tools
(such as power spectra, phase portraits, Lyapunov exponents and fractal di
mensions) suggest a chaotic behavior of deterministic nature. The distance
of the first band from the interface is plotted versus time. The velocity o
f dissolution is determined by obtaining a functional fit from the time var
iation curve and then calculating a derivative curve of that fit. The deriv
ative is particularly evaluated at t = 10 and 15 days (taken as reference d
ays), thus yielding the velocity of the dissolution front. A;similar method
is used for the distance of the last band from the interface, to determine
the velocity of the precipitation front. The measurements are performed fo
r five different concentrations (C) of cobalt chloride and the dependence o
f the two front velocities on Cis investigated. Both front velocities are f
ound to decrease monotonically with increasing C with a linear correlation
existing between them.