C. Rey

Thermogenesis: identification and deconvolution in microcalorimetric systems with continuous injection for the study of liquid mixtures

The results obtained by means of different identification methods, tested on the experimental thermograms of calorimeters with a continuous injection device, are compared. The experimental system is specially suited to investigating the thermodynamic properties of mixtures. Particular attention is devoted to defining the conditions that allow a satisfactory approach to the transfer function of the system at the beginning of the injection. The accuracy of such an approach determines that of the excess enthalpies measured at large dilutions.

Excess volumes of (n-heptane + n-octane + cyclohexane) at 298.15 K

Abstract Excess volumes of ( n -heptane + n -octane), ( n -heptane + cyclohexane), ( n -octane + cyclohexane), and ( n -heptane + n -octane + cyclohexane) have been determined from density measurements at 298.15 K. Various ways of predicting the excess volumes of the ternary mixture from experimental results for the binary mixtures are compared.

Deconvolution in conduction calorimeters: An analytical treatment and experimental results from the pulsed transfer function

Abstract Various techniques may be employed to approximate thermogenesis in conduction calorimeters by studying the transfer function (harmonic analysis, time domain analysis, analogue and digital filters, etc.). This article describes the use of the pulsed transfer function and Truxals method of compensation as a technique suitable for employing with data sampling systems in the low frequency domain. The theory developed is applied experimentally to a Calvet conduction calorimeter, which is shown to require a compensating plant.

Thermogenesis: Smoothing techniques in Z-transform and harmonic analysis

Abstract This work analyses how the standard smoothing techniques affect the thermogenesis given by harmonic analysis or Z-transform methods. The analysis has allowed an optimization of their efficiency. The results concerning signal/noise ratios of 40, 60, 80 and 100 dB are tabulated and generalized to a reduced frequency representation.

Deconvolution in microcalorimetry and an application to mass-varying systems

The behaviour of the calorimetric response in continuous injection devices, which are well suited for measurement of excess partial molar enthalpies at different concentrations, is analysed by means of heat transport models. Signal analysis of the thermal response gives the enthalpy values at very low concentrations. We establish an operating routine for the identification of the time-varying device, and a generalized deconvolution procedure to obtain, with high accuracy, the power released in the calorimeter as a function of time. The main features considered are the changes in sensitivity and dynamic properties of the experimental system due to the injection of one component in the mixture. A formal decomposition of the heat transport equations shows that typically time-invariant methods are able to deal with deconvolution in non-invariant systems.

Excess volumes of (n-heptane + n-nonane + cyclohexane) and (n-heptane + n-decane + cyclohexane) at 298.15 K

Abstract Excess volumes of (n-heptane + n-nonane), (n-nonane + cyclohexane), (n-heptane + n-decane), (n-decane + cyclohexane), (n-heptane + n-nonane + cyclohexane), and (n-heptane + n-decane + cyclohexane) have been determined from density measurements at 298.15 K. Various ways of predicting the excess volumes of the ternary mixtures from experimental results for the binary mixtures are compared.

Evaluation of solute distribution coefficients in solubilized systems

A theoretical treatment is proposed for the determination of the distribution characteristics of a solubilizate between micellar and aqueous phases from the variation of the critical micelle concentration (CMC) with the molar ratio of components in the system. The theory has been tested by determining the distribution coefficient and free energy of solubilization of n-butanol in the n-butanol/sodium dodecyl sulphate/water system from CMC values determined by conductimetric techniques.

The identification of variable mass conduction calorimetry systems

Abstract A technique to characterize calorimetric systems which uses a non-linear curve-fitting algorithm to approximate their unit pulse response has been tested satisfactorily and applied to the variable mass case of a calorimeter working with a continuous mixing device.

THE APPLICATION OF DECONVOLUTION CALORIMETRY TO THE BELOUSOV-ZHABOTINSKII REACTION

In the present paper we describe the determination of heat generation curves of the Belousov-Zhabotinskii reaction for various concentrations of reagents using deconvolution techniques. The experiments were carried out in a twin-vessel Calvet-type conduction calorimeter. The force of the injected jet guaranteed the initial homogeneity of the reaction mixture, and no subsequent stirring was employed. Some characteristic parameters have been calculated from the deconvoluted signal.

Excess volumes of (n-heptane + n-undecane) between 288.15 and 308.15 K

Excess molar volumes of (n-heptane + n-undecane) have been determined from density measurements at 288.15, 293.15, 298.15, 303.15, and 308.15 K, and an approximation to (∂VmE∂T)p in the neighbourhood of 298.15 K has been calculated.