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Abstract  

The conductivities of binary mixtures of glycerine and water were measured at 20C by means of a transient method. The equation describing the correlation between concentration and thermal conductivity was determined. The equation can be used for determining concentrations in mixtures. The results show that (1) the error in the determination of the molar concentration of water in mixtures is less than 1%, (2) the time of measurement is 1 s, (3) this method can be used for on-line analysis in production control.

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6 where V m is the molar volume and π is the internal pressure. Excess Gibb’s free energy of activation 7 The strength of interaction between the component molecules of binary mixtures is well reflected in the deviation of the

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Solid–liquid phase diagrams of binary mixtures

Acetylsalicylic acid(1) + E(2) (E = salicylic acid, polyethylene glycol 4000, d-mannitol)

Journal of Thermal Analysis and Calorimetry
Authors: Luigi Campanella, Valentina Micieli, Mauro Tomassetti and Stefano Vecchio

Abstract  

This study reports the investigation of three binary mixtures represented by acetylsalicylic acid (ASA) with its most important degradation product, salicylic acid (SA), and two of the most commonly used excipients (polyethylene glycol 4000 (PEG-4000) and d-mannitol (MA)). The liquidus and solidus equilibrium temperatures determined by DSC for pure components and solid binary mixtures at a fixed composition (mass fraction of ASA, w) were used to construct the corresponding solid–liquid phase diagrams. On the basis of the DSC results, the binary mixtures ASA/SA and ASA/PEG exhibit eutectic behavior (T eu = 155.0 ± 0.5 °C, w eu = 0.55 ± 0.02 and T eu = 53.3 ± 0.5 °C, w eu = 0.32  ± 0.01 ), respectively), while the binary mixture ASA/MA revealed the presence of a monotectic with a mean melting temperature of 162.2 °C in the range 0.2 < w 1 < 0.8. The composition of the two eutectics formed was confirmed by the related Tamman triangles. Finally, the liquidus curves of ASA/SA and ASA/PEG mixtures were also successfully predicted providing suitable polynomial (second-order) fitting equations.

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Thermodynamic properties of binary mixtures containing oxaalkanes

Part V. Monoethers, acetals, polyethers, cyclic mono- and di-ethers+benzene

Journal of Thermal Analysis and Calorimetry
Authors: B. Marongiu, Alessandra Piras, Silvia Porcedda and Enrica Tuveri

Abstract  

A flow microcalorimeter has been used to determine excess enthalpies, H E, at 298.15 K of binary mixtures of dipentylether, dihexylether, 1,2-dimethoxyethane and 1,2-diethoxyethane (1)+benzene (2). These data along with the data available in the literature on H E, molar excess Gibbs energies, G E and liquid-vapour equilibria (LVE) of non-cyclic monoethers, acetals, polyethers and of cyclic mono- and di-ethers+benzene are examined on the basis of the DISQUAC group contribution model. Using a set of adjusted interchange energies parameters, structure dependent, the model provides a fairly consistent description of the thermodynamic properties as a function of concentration. The interaction parameters, dispersive and quasichemical, depend on the intramolecular environment of the O atom. There is clear evidence for the steric and inductive effects exerted by the alkyl groups adjacent to the O atom, for -O-C-O- proximity effect and for a ring strain effect. The steric effect results in a regular decrease of the dispersive interaction parameters of the oxygen/benzene (e,b) contact; The proximity effect of the O atoms produces a regular decrease and the ring strain a regular increase of the dispersive interaction parameters; the quasi-chemical remain constant.

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Abstract  

Thermogravimetric analysis is used to determine the amounts of Mg(OH)2 and Mg(CH3COO)2in a mixture thereof. The application and suitability of different analysis methods are discussed. In the first method the mass losses in the temperature ranges as indicated by the decomposition of the pure compounds were used. Results obtained using these temperature ranges were unusable. The percentage mass losses due to the decomposition of Mg(OH)2 and Mg(CH3COO)2 were then determined in a second method using the minimum in the derivative mass vs. temperature curves. The results obtained by this method compared well with the actual values for mixtures containing more than 15% magnesium acetate. The third method employed the total experimental mass loss of both decomposition reactions. The results obtained using this method compared well to the actual values, giving a R 2 value of more than 0.99. This method of using the total mass losses can however only be used for binary mixtures that consist only of magnesium hydroxide and magnesium acetate.

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Abstract  

The excess molar enthalpies HE of binary mixtures of formamide with N-methylformamide, N-ethylformamide, N-methylacetamide, N-ethylacetamide and N-methylpropion-amide have been measured as functions of the mole fraction at 308.15 K, using an isoperibol rotating calorimeter. The experimental values of HE are negative for all mixtures over the whole composition range. Intermolecular interactions in these mixtures are discussed through comparison of the results with those for corresponding binary mixtures of water.

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Abstract  

Pyrolytic process has a promising potential for the environmentally friendly upgrading of lignocellulosic and plastic waste. Thermogravimetry and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) were used to get information about the reactive decomposition of PCL in binary mixtures with microcrystalline cellulose (MC) or sisal fibres (SF). Preliminary thermogravimetric investigation showed that biomass is thermally degraded at lower temperatures than PCL and this process has a predominant influence on the thermal behaviour of the mixtures. Discrepancies between the experimental and predicted TG/DTG profiles were considered as a measurement of the extent of interactions occurring on co-pyrolysis. It was found that reactivity of PCL was slightly increased in PCL-SF binary mixtures. Evolution of acidic products from cellulose and hemicelluloses decomposition may promote PCL degradation in binary mixtures with SF. It seems that the co-pyrolysis process could have potential for the environmentally friendly transformation of biocomposites.

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Abstract  

Gamma-radiolysis of alkaline binary mixtures of nitrate-alcohol (1-propanol and 1-butanol) has been investigated at a fixed pH of 12. The products of radiolysis, mainly nitrite, aldehyde and hydrogen peroxide were estimated. Also the effect of concentration of each species present in the mixture on the G-values of the products formed has been examined. The G-values of each of the products are found to be lower in basic medium in binary mixtures as compared to those obtained at neutral pH; other conditions being kept constant. However, the yields of products in nitrate solutions show higher values at basic pH in comparison with their counterparts at neutral pH. Results are explained on the basis of reaction mechanism that operates during the process of radiolysis, leading to the formation of the different products.

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Abstract  

Differential scanning calorimetry (DSC) was used to construct phase diagrams of binary mixtures of alkylcyclohexanes and to characterize metastable phases formed in the binary mixtures. The experimentally measured liquidus curves were compared to the liquidus curves calculated using ideal solution theory. The measured phase diagrams of pentadecylcyclohexane/nonadecylcyclohexane and octadecylcyclohexane/nonadecylcyclohexane binary mixtures are consistent with theoretical phase diagrams constructed based on the assumption that these mixtures form eutectic systems. It was also observed that a metastable phase formed in some binary mixtures of pentadecylcyclohexane/nonadecylcyclohexane under fast cooling conditions. It is hypothesized that this metastable phase recrystallizes into the eutectic phase upon heating.

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Journal of Thermal Analysis and Calorimetry
Authors: S. Cebreiro, M. Illobre, M. Mato, V. Verdes, J. Legido and M. Paz Andrade

Abstract  

We have determined the excess molar enthalpies H m E at 298.15 K and normal atmospheric pressure for the binary mixtures containing tert-butyl methyl ether (MTBE)+(methanol, ethanol, 1-propanol, 1-pentanol) using a Calvet microcalorimeter.

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