Residual differences after model fitting were investigated in both isothermal and non-isothermal kinetics in order to make
numerical comparisons between several models and various parameter-estimating methods. Data from two independent experimental
series were evaluated.
A large data set, collected earlier under isothermal conditions from decompositions and hydrothermal reactions of aluminium
hydroxides and oxides, was processed first. It showed that mechanical activation of the starting gibbsite affected reactivity
of samples in several subsequent reactions for all model equations tried. The relative residual deviation concept is introduced,
and statistics were applied to find a model that fits a certain reaction in most of the cases.
In the second study, the sulphate decomposition step of aluminium sulphate octadecahydrate was investigated. TG curves were
measured using a constant heating rate. Dynamic models were fitted by three mathematical methods, including a new general
purpose one. Fitting ability of the methods with various complexity were compared on the basis of residual deviations obtained
after integration of the model equations. As well as evaluating the best fit, this new parameter-estimating method provides
a statistical analysis of the reliability of the whole model fitting process.