Analysis of DTA curves and calculation of kinetic data using computer technique

Principles of two computer programs useful for the evaluation of heterogeneous kinetics are described.The first program ALANTA allows to obtain the non-isothermal kinetic curve from the shape of general DTA peak using the DTA-equation derived elsewhere¹.The second program SQUEST determines the kinetic mechanism which is the most appropriate to a given non-isothermal kinetic curve and evaluates the corresponding kinetic parameters. The program decides between 19 kinetic models and uses both integral and differential methods of evaluation.     

Salt and medium effects in the aquation ofcis-amminebromobis(ethylenediamine)cobalt(III) ion

Summary The aquation kinetics ofcis-[Co(NH₃)Br(en)₂]²⁺ were studied in aqueous and mixed aqueous-nonaqueous solvents in the presence of KBr, KCl, LiCl, NaNO₃ and NaClO₄ as supporting electrolytes. It was found that the association between the complex ion and Cl^–, Br^– and NO ₃ ^– ions takes place. The association constants, K_IP, were evaluated from kinetic measurements. The kinetic parameters in the studied media are related to the influence of the cosolvents on the solvation spheres of the reactants and activated complex.     

Heat capacity equations for nonstoichiometric solids

The equations for heat capacity measured under isodynamical conditions (fixed activity of a single component) are derived for partly open systems exchanging one component with the surroundings while keeping the contents of all other components constant. Compared to conventional isobaric (and isoplethal) heat capacity of a strictly stoichiometric phase, the isodynamical heat capacity of a nonstoichiometric phase is found to involve two additional terms—the saturation contribution due to incorporation (or release) of the free component and the contribution due to deviation from stoichiometry reflecting a different number of the involved phonon modes (due to different free component content) and in some cases a variation of free component incorporation mechanism.     

Kinetics of oxidation of pentaammine-isothiocyanato-cobalt(III) ion with peroxodisulphate and periodate in water and water-organic mixtures

Summary The kinetics of oxidation of [Co(NH₃)₅(NCS)]²⁺ by peroxodisulphate and periodate were investigated at different ionic strengths, and at different temperatures and concentrations of perchloric acid. Rate constants and activation parameters are also reported in mixed water-organic solvents. It was shown that the acid-base equilibria involving S₂O ₈ ⁻² , and IO ₄ ⁻ ions are important in the reactions studied. Solvent effects on the oxidation are interpreted in terms of the solvation of both the initial state and the activated complex.     

Complete classification of local conservation laws for generalized Cahn–Hilliard–Kuramoto–Sivashinsky equation

In this paper, we consider nonlinear multidimensional Cahn–Hilliard and Kuramoto–Sivashinsky equations that have many important applications in physics and chemistry, and a certain natural generalization of these two equations to which we refer to as the generalized Cahn–Hilliard–Kuramoto–Sivashinsky equation. For an arbitrary number of spatial independent variables, we present a complete list of cases when the latter equation admits nontrivial local conservation laws of any order, and for each of those cases, we give an explicit form of all the local conservation laws of all orders modulo trivial ones admitted by the equation under study. In particular, we show that the original Kuramoto–Sivashinsky equation admits no nontrivial local conservation laws, and find all nontrivial local conservation laws for the Cahn–Hilliard equation.     

Medium effect in the base hydrolysis of pentaamminebromocobalt(III) ion

Summary The effect of organic cosolvent on the rate constant of the base hydrolysis of pentaamminebromocobalt(III) ion was investigated in mixtures of H₂O with MeOH, EtOH,i-PrOH,t-BuOH, and dioxane. The thermodynamic transfer functions, corresponding to the transfer of reactants and activated complex from water to the solvent mixtures, were evaluated from kinetic measurements and from solubilities of the complex salt. The experimental results are in good agreement with a dissociative mechanismvia the conjugate base.     

Solvent effect on the initial state and transition state of anation of pentaammine-aquachromium(III) ion by thiocyanate

Summary Solvent effects on rate constants and activation enthalpies and entropies for the anation of [Cr(NH₃)₅H₂O]²⁺ by SCN^- in aqueous mixtures of MeOH, EtOH, i-PrOH and t-BuOH were analysed into initial and transition state contributions. From kinetic measurements, solubilities of the complex salt and enthalpies of solution, the thermodynamic transfer functions G _inft ^supo , H _inft ^supo and S _inft ^supo , corresponding to the transfer of reactants and activated complex from water to aqueous-organic mixtures, were evaluated. The very small difference in solvation of initial and transition states, indicated by the analysis, seemed to be consistent with the proposed interchange mechanism.