Chapter 3 - Kinetic Background to Thermal Analysis and Calorimetry

Selected kinetic and mechanistic studies of thermal reactions of initially solid substances are reviewed with emphasis on the evidence that some of these chemical changes proceed with the essential participation of melting. The reactions considered are classified on the extent and the role of such melting and the various types of behaviour observed are discussed with reference to solid state rate processes in crystals.

Thermal reactions of selected solids including reactants that melt during chemical change

A kinetic and mechanistic study of the thermal decomposition of nickel acetate

This chapter deals with fundamental studies of the chemistry of water elimination reactions from crystals, including characterization of the controls of reactivity together with the kinetics and mechanisms of the rate processes that participate The endothermic and reversible character of most dehydrations, calorimetry, experimental methods, thermal analysis, and individual accounts of a representative range of diverse dehydrations illustrates many different characteristic features of the reactions Crystalline solids that evolve water on heating do not always, or necessarily, contain molecular H 2 O, but water may be formed through thermal reactions between crystal components before subsequent release During the precursor H 2 O evolution, the originally prepared solid has certainly undergone extensive reorganization This includes the possibility of crystal structure changes, particle sizes and textures, imperfection numbers, and distributions Many dehydrations are initiated at, or very close to, a crystal surface, by the formation of a particle of solid product termed as nucleation

Chapter 12 - Dehydration of Crystalline Hydrates

PREFACE The position and importance of thermal analysis among methods of material research and structure elucidation is well shown by the review which appeared in Research and Development Journal.1 According to the review, about 42% of the laboratories surveyed are using, or expect to be using in the near future, thermogravimetric (TG), differential thermal analysis (DTA), or differential scanning calorimetric (DSC) devices. It is also characteristic that about 1 to 2% of the papers appearing yearly on analytical chemistry deal with the problems of thermal analysis.2,3 It is clearly shown by these data that thermal methods of analysis cannot compete with electroanalytical, spectroscopic, and chromatographic methods with respect to practical applications. Nevertheless, they play an important part in material research. If used and interpreted properly, methods of thermal analysis provide unique information in both theoretical and practical respects about the thermal behavior of samples.

Modern Methods of Thermal Analysis

Nucleus formation and the kinetics of thermal decomposition of nickel formate

Information concerning the nucleation process in the thermal decomposition of nickel formate has been obtained from kinetic and electron microscopic observations. The rate of the initial acceleratory stage of reaction and shape of the yield-time curve for isothermal reaction are sensitive to reactant configuration. This is attributed to variations in the local availability of water vapour, believed to inhibit the nucleation step. The formation of nuclei within the reactant mass is also inhomogeneous, again attributable to changes in the prevailing water vapour pressure. Some kinetic and mechanistic implications of these observations are discussed.

M. J. McGinn

Papers

Nucleus formation and the kinetics of thermal decomposition of nickel formate

Nucleation Process in the Decomposition of Nickel Formate