A prototype statistical model for the etching of a random solid is
investigated in order to assess the influence of disorder and temperature on
the dissolution kinetics. At low temperature, the kinetics is dominated by
percolation phenomena, and the percolation threshold determines the global
reaction time. At high temperature, the fluctuations of the reaction rate are
Gaussian, whereas at low temperature they exhibit a power law tail due to
chemical avalanches. This is an example where microscopic disorder directly
induces non-classical chemical kinetics.Comment: Revtex, 4 pages, 5 figure
