Thermodynamics of Amide + Amine Mixtures. 1. Volumetric, Speed of Sound, and Refractive Index Data for N,N-Dimethylformamide + N-Propylpropan-1-amine, + N-Butylbutan-1-amine, + Butan-1-amine, or + Hexan-1-amine Systems at Several Temperatures Hevia, F.; Cobos, A.; González, J.A.; García de la Fuente, I.; Sanz, L.F.; Journal of Chemical & Engineering Data 2016, 61, 1468-1478