Criteris for deciding upon the support effect by the thermal decomposition of precursor/support systems are discussed. Instead
of the linear relationship between lgA and E, two new criteria determined by the calculated rate maximum were suggested. Dimensionless criteria based on the rate, conversion
and temperature values at the inflexion point of the TG diagram lead to a parameter able to describe the support effect in
a synthetic and quantitative manner. The experimental data were the TG-curves for the decomposition of ammonium metavanadate,
molybdic acid and ammonium phosphomolybdate, supported on carborundum and silica.