Compressibilités de l'eau et du benzène dans tout le domaine de miscibilité du système eau + 2-propanol + benzène

Sound velocities have been measured over the whole miscibility domain of the water + 2-propanol + benzene system. The apparent molar isentropic compressibilities of benzene and water were calculated from these data. The apparent molar compressibilities of benzene and water present large changes in the water-rich and benzene-rich regions, respectively, whereas the changes are smooth in the intermediate region. These results suggest that microtransitions similar to the formation of micelles and inverse micelles occur at the two ends of the phase diagram. The regularity of the intermediate region is consistent with a bicontinuous model of microemulsions. For the water-rich region, the compressibilities of transfer of benzene at infinite dilution, from water to water + 2-propanol mixtures, were simulated with the model of Roux and co-workers. This simulation tends to confirm that the alcohol and the benzene form mixed aggregates. Keywords: compressibility, ternary system, microemulsion, water, benzene, 2-propanol.

Ultrasonic velocity, excess adiabatic compressibility, apparent molar volume, and apparent molar compressibility properties of binary liquid mixtures containing 2-butoxyethanol

Ultrasonic velocity and density data of binary systems of water–2-butoxyethanol (BE), 2-butoxyethanol-benzene, and 2-butoxyethanol–decane are reported for temperatures of 25, 40, and 55 °C. Adiabatic compressibility coefficients, apparent molar volumes, and apparent molar compressibilities were calculated from these data. Excess adiabatic compressibility properties were evaluated using volume fraction weighting of the individual component properties to estimate ideal mixture behavior. These results are compared with the data obtained based on the use of mole fraction weighting of the individual component properties for the ideal behavior value. A sharp ultrasonic velocity maximum and compressibility minimum is observed at low BE concentration in mixtures of water–BE at all temperatures. These maxima in ultrasonic velocity and minima in adiabatic compressibility are attributed to the formation of "clathrate-like" structures of water and alcohol. A shift of the velocity maximum towards lower concentrations of BE was observed with increase of temperature. A minimum in the ultrasonic velocity and a maximum in adiabatic compressibility coefficient values are observed in systems of BE–benzene and BE–decane. These results are discussed in terms of the breakdown of associated alcohol structures and the interstitial location of hydrocarbon molecules in alcohol aggregates.