No abstract available

No abstract available

[en] Short communication

[en] The exchange of CH₄ in tritium has been measured at concentrations of 1.45 and 3.00 mol% to display the time evolution of CT₄. It is observed that the total methane concentration decreases with time, and no masses >24 amu are observed using mass spectroscopy. After 18 months, only 0.2% CT₄ gas remained in the 3.00% CH₄ experiment. These observations indicate that carbon is being removed from the gas phase. A model based on ion/molecule interactions is presented to explain the formation of CT₄ and free carbon. 9 refs., 4 figs., 1 tab

[en] A combined experimental and theoretical study was undertaken to explore the role of dimensionality and spatial extent in influencing intramicellar kinetic reactions. Three qualitatively different types of energy-transfer reactions were studied: (1) the diffusion of a confined photoexcited species to a reactive surface; (2) the energy transfer between two completely compartmentalized reactants; and (3) the chemical reaction between species restricted in their diffusional motion to the surface of the micelle. The theoretical framework within which the dynamics of these three processes were studied was the continuum theory of reaction-diffusion kinetics. It was found that the theory developed correctly predicts the emergence of pseudo-first-order behavior, with attendent (effective) rate constants in qualitative (and near quantitative) accord with the experimental results

[en] The author presents arguments to alleviate any possible misunderstanding that might result from the paper by Bloch and Mintz in which the perfusive precipitation model, which has been successfully applied to the U-H system, was given an abrupt dismissal. (Auth.)

[en] Chemical kinetics of the reaction of pinacolone with deuterium was studied. The rate constant for this first-order reaction was determined

[en] MAKSIMA-CHEMIST was written to compute the kinetics of simultaneous chemical reactions. The ordinary differential equations, which are automatically derived from the stated chemical equations, are difficult to integrate, as they are coupled in a highly nonlinear manner and frequently involve a large range in the magnitude of the reaction rates. They form a classic 'stiff' differential equaton set which can be integrated efficiently only by recently developed advanced techniques. The new program also contains provision for higher order chemical reactions, and has a dynamic storage and decision feature. This permits it to accept any number of chemical reactions and species, and choose an integraton scheme which will perform most efficiently within the available memory. Sparse matrix techniques are used when the size and structure of the equation set is suitable. Finally, a number of post-analysis options are available, including printer and Calcomp plots of transient response of selected species, and graphical representation of the reaction matrix. (auth)

[en] The kinetics of the chlorination of NB has been studied by a microcalorimetric method. The experimental results show that the niobium pentachloride produced during the reaction is immediately volatilized and that the linear rate of the process is proportional to square root of pressure of chlorine. These results are explained by the adsorption of chlorine on niobium as process limiting the reaction rate

[en] A discussion of the application of the rule of geometric mean to heavy atom kinetic isotope effect of reactions with complex mechanisms is presented. It is shown that the rule fails in the case of secondary heavy atom kinetic isotope effects