Thermodynamics of organic mixtures containing amines -: III:: Molar excess volumes at 298.15K for tripropylamine plus n-alkane systems -: Application of the Flory theory to N,N,N-trialkylamine plus n-alkane mixtures

Molar excess volumes at 298.15 K and atomospheric pressure for tripropylamine + n-hexane, + n-octane, + n-decane, + n-dodecane or + n hexadecane systems determined from densities measured with an Anton-Paar DMA 602 vibrating-tube densimeter are reported. N,N,N-trialkylamihe + n-alkane systems have been studied using the Flory theory. Better results on excess enthalpies are obtained when the difference in size between the mixture components is large. The dependence of the excess volume at equimolar composition with the length of the n-alkane is correctly described. The simultaneous analysis of the experimental excess volumes and of the excess enthalpies reveal that free volume effects are important in systems formed by triethylamine or tripropylamine and longer alkanes, as well as in those involving tripropylamine or tributylamine and the shorter alkanes. The Patterson effect is present in the studied mixtures. The more globular amines, triethylamine, tripropylamine or tributylamine are order breakers of the longer alkanes. The amines of very large size, e.g., tridodecylamine, show an ordered structure.