Excess enthalpies and excess volumes of binary mixtures containing a linear carboxylic acid + di-iso-propyl ether at 298.15 K and 0.1 MPa

PORCEDDA, SILVIA;Leo, Maurizio;USULA, MARIANNA;PIRAS, ALESSANDRA

2016-01-01

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Abstract

Molar heat of mixing and volume change of mixing, coinciding with molar excess enthalpies, HE, and molar excess volumes, VE, respectively, of binary mixtures composed by a linear saturated aliphatic acid of general formula: CH3(CH2)u-2–CO2H [u = 2, 3, 4, 5, 6, 7, 8] + di-iso-propyl ether, [(CH3)2CH−]2O, have been measured in the whole range of mole fraction at 298.15 K and 0.10 MPa. The HE experimental determinations have been realized by means of a mixing flow calorimetric apparatus, and VE have been calculated from density data acquired by using a vibrating tube densitometer. Mixing is exothermic for all investigated systems. The values at equimolar composition, Hx=0.5E, are in the range: (−385 ± 1 to −140 ± 4) J mol−1. The more negative value is attributable to butanoic acid-containing mixture; then, HE decrease in absolute value as the alkyl chain of the acid increases. For the same systems, the VE trends are different: the value at equimolar composition, Vx=0.5E, always negative, increase regularly in absolute value as the alkyl chain length of the acid increases from –1.12 × 10−6 m3 mol−1 for mixtures containing ethanoic acid to −1.75 × 10−6 m3 mol−1 for octanoic acid-containing mixtures.