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Excess molar volumes VE at 298.15 K were determined by means of a vibrating tube densimeter for binary mixtures of {heptane + open chain secondary (diethyl to dibutyl) and tertiary (triethyl to tripentyl) amines} as well as for cyclic imines (C2, C3, C4, C6, and C7) and primary cycloalkylamines (C5, C6, C7, and C12). The VE values were found positive for mixtures involving small size amines, with VE decreasing as the size increases. Negative VE’s were found for tributyl- and tripentylamine, heptamethylenimine, and cyclododecylamine. Mixtures of heptane with cycloheptylamine showed an s-shaped curve. Partial molar volumes V ∘ of amines at infinite dilution in heptane were obtained from VE and compared with V ∘ of hydrocarbons and other classes of organic compounds taken from literature. An additivity scheme, based on the intrinsic volume approach, was applied to estimate group (CH3, CH2, CH, C, NH2, NH, N, OH, O, CO, and COO) contributions to V ∘ . These contributions, the effect of cyclization on V ∘ , and the limiting slope of the apparent excess molar volumes were discussed in terms of solute–solvent and solute–solute interactions.

Excess molar volumes VE at 298.15 K were determined by means of a vibrating tube densimeter for binary mixtures of heptane + primary n-alkyl (C3 to C10) and branched amines (iso-propyl-, iso-, sec-, and tert-butyl-, iso-, tert-pentyl-, and pentan-3-amine) in the whole composition range. The apparent molar volumes of solid dodecyl- and tetradecylamine in heptane dilute solution were also determined. The VE values were found positive for mixtures involving C3 to C8 linear amines, with VE decreasing with chain lengthening. Heptane + nonyl and decylamine showed s-shaped, markedly asymmetric, curves. Mixtures with branched C3 to C5 amines displayed positive VE’s larger than those observed in the mixtures of the corresponding linear isomers. Partial molar volumes V° at infinite dilution in heptane were evaluated for the examined amines and compared with those of alkanes and alkanols taken from the literature. An additivity scheme, based on the intrinsic volume approach, was applied to estimate group (CH3, CH2, CH, C, NH2, and OH) contributions to V°. The effect of branching on V° and the limiting slope of the apparent excess molar volumes were evaluated and discussed in terms of solute–solvent and solute–solute interactions.

The excess molar volumes V m E at T =298.15 have been determined in the whole composition domain for (2-methoxyethanol + tetrahydrofuran + cyclohexane) and for the parent binary mixtures. Data on V m E are also reported for (2-ethoxyethanol + cyclohexane). All binaries showed positive V m E values, small for (methoxyethanol + tetrahydrofuran) and large for the other ones. The ternary V m E surface is always positive and exhibits a smooth trend with a maximum corresponding to the binary (2-methoxyethanol + cyclohexane). The capabilities of various models of either predicting or reproducing the ternary data have been compared. The behaviour of V m E and of the excess apparent molar volume of the components is discussed in both binary and ternary mixtures. The results suggest that hydrogen bonding decreases with alcohol dilution and increases with the tetrahydrofuran content in the ternary solutions.

Excess molar volumes VmEof {di- n -butyl ether (DBE) + a monofunctional organic compound} have been determined atT = 298.15 K over the whole composition range by means of a vibrating-tube densimeter. TheVmE values were either positive (propylamine, or butylamine, or acetone, or tetrahydrofuran + DBE) or negative (methanol, or butanol, or diethyl ether, or cyclopentanone, or acetonitrile + DBE). Markedly asymmetric VmEcurves were displayed by (DBE + methanol) and (DBE + acetonitrile). Partial molar volumes __ Vmoat infinite dilution in DBE, both from this work and the literature, were analysed in terms of an additivity scheme, and the group contributions thus obtained were discussed and compared with analogous results in water. DBE revealed a greater capability of distinguishing between polar and non-polar solutes, as well as in discriminating differently shaped molecules (unbranched, branched, cyclic). The limiting slopes of apparent excess molar volumes are evaluated and briefly discussed in terms of solute–solute and solute–solvent interactions.