V. Perez Villar

Excess enthalpies of (n-alkanol + dipropylether), (n-alkanol + 1,2-diethoxyethane), and (n-alkanol + 2-ethoxyethanol) at 298.15 K

Abstract Using a Calvet microcalorimeter, we have determined at 298.15 K and normal atmospheric pressure the excess molar enthalpies HmE of binary mixtures formed by dipropylether, 1,2-diethoxyethane, or 2-ethoxyethanol as one component and 1-butanol, 1-pentanol, or 1-hexanol as the other. A variable-degree empirical polynomial in the mole fraction of n-alcohol has been fitted to the results.

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.

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.

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.

A model for variable mass calorimetry systems

In continuous injection calorimeter systems the mass of the contents of the calorimeter cell varies. This article describes a mathematical model for microcalorimeter systems employing this technique. By assuming the heat capacity of the variable element to depend linearly on time, an analytical expression for the transfer function of the system can be obtained. As an example, the unit pulse response calculated for a variable mass calorimeter by numerical methods is compared graphically with that predicted by the model when just two time constants are taken into account.

Characterization of calorimeters using the Z transform

Abstract This article presents a new method of characterizing calorimeters based on the Z transform of the systems unit pulse response. Results are presented for various signal-to-noise ratios. As well as giving numerical values for the parameters of the calculator, the method proposed determines the optimal number of such parameters for the description of the system.

A noise filter for calorimeter signals

Abstract This article describes a general method for filtering noise from thermograms which uses the previously determined autocorrelation function of the noise produced by the calorimeter apparatus together with an estimate of the second derivative of the signal being processed. The method is applied to a standard Calvet microcalorimeter, the autocorrelation function of whose noise is shown, and the variable number of points required by the filter in this case is plotted against a convenient function of the second derivative of the signal. Comparison of deconvolved calorimeter output signals with and without previous filtering shows the filter to function as desired.