Thermodynamische Untersuchungen zur Lewis-Acidität von Trimethylchlorsilan - die Phasendiagramme und Exzeßvolumina der Systeme (CH3)3SiCl/Pyridin und (CH3)3CCl/Pyridin / Thermodynamic Examinations on the Lewis Acidity of Trimethylchlorosilane - the Phase Diagrams and Excess Volumes of the Systems (CH3)3SiCl/Pyridin and (CH3)3CCl/Pyridin

The isobaric melting and boiling diagrams for the systems: trimethylchlorosilane/pyridine and trimethylchloromethane/pyridine are reproduced. Some measurements of the molar volume of mixtures between trimethylchlorosilane and pyridine and trimethylchloromethane and pyridine are reported. For both systems the molar excess volume has been calculated as a function of the mole fractions

Phasendiagramme und Exzeßvolumina der Systeme (CH3)2SiCl2/Pyridin und (CH3)2CCl2/Pyridin / Phase Diagrams and Excess Volumes of the Systems (CH3)2SiCl2/Pyridine and (CH3)2CCl2/Pyridine

The isobaric melting and boiling diagrams for the systems: dimethyldichlorosilane/pyridine and 2,2-dichloropropane/pyridine are reproduced. The existence of the incongruently melting addition compounds (CH3)2SiCl2 · (Pyridine)2 and [(CH3)2CCl2]3 · Pyridine could be proved. Some measurements of the molar volume of mixtures of pyridine and dimethyldichlorosilane, and pyridine and 2,2-dichloropropane are reported. For both systems the molar excess volume has been calculated as a function of the mole fractions.

Thermodynamische Untersuchungen der Systeme Pyridin/CH3SiCl3 und Pyridin/Cl3CCH3 / Thermodynamic Examinations of the Systems Pyridine/CH3SiCl3 and Pyridine/Cl3CCH3

The isobaric melting and boiling diagrams for the systems: pyridine/methyltrichlorosilane and pyridine/1,1,1-trichloroethane are reproduced. The existence of the congruently melting addition compound CH3SiCl3· (Pyridin)2 could be confirmed. Some measurements of the molar volume of mixtures between pyridine and methyltrichlorosilane and pyridine and 1,1,1-trichloroethane, respectively, are reported. For both systems the molar excess volume and for the system pyridine/methyltrichlorosilane the molar excess enthalpie have been calculated as a function of the mole fractions.

Excess volumes for ethanol + water mixtures at 10-K intervals from 278.15 to 338.15 K

The excess volumes of mixtures of xA ethanol+ xB water have been measured at 10-K intervals from 278.15 to 338.15 K over the whole composition range, various dilution dilatometers being used. Particular attention has been paid to regions dilute in both ethanol and water. The partial molar excess volume of ethanol at infinite dilution in water is extremely temperature-dependent, becoming more negative as the temperature increases. The partial molar excess volume of ethanol in dilute solutions is very concentration-dependent at low temperatures but the dependence approaches zero at 362 K. At an xA value of 0.038, the partial molar excess volume of ethanol VEA is independent of temperature, having a value of -5.23 cm3 mol-1, while the excess volume VEA is independent of temperature at xA = 0.082, having a value of -0.420 cm3 mol-1. These unusual observations are explained in terms of the variation of the temperature of maximum density with composition for dilute ethanol solutions. At high mole fractions of ethanol the excess volume and the partial molar excess volume of water do not show unusual behaviour.

Thermodynamic Excess Functions for the Liquid System W ater + Acetic Acid from Calorimetric Data

For the liquid system water + acetic acid, we give the results of new calorimetric measurements regarding the molar excess enthalpy H̅E for 25 °C, 30 °C, 35 °C, 40 °C, 55 °C, and 70 °C, covering nearly the entire range of com­ positions. The experimental data show that H̅E is positive for all compositions and temperatures except in the region of low acid concentrations at temperatures below 55 °C where the process of mixing the pure liquid components is exothermic (H̅E<0). Using values of the molar excess Gibbs function G̅E (always positive) derived from earlier data on vapour-liquid equilibria, we compute the molar ex­cess entropy S̅E which is always negative. The “symmetryrule” concerning the composition dependence of G̅E (as compared to that of H̅E and S̅E) has again been confirmed. The composition dependence of S̅E is similar to that of the molar excess volume.