Apparent molar volumes and apparent molar heat capacities of aqueous solutions of isomeric butanols at temperatures from 278.15 K to 393.15 K and at the pressure 0.35 MPa

Apparent molar heat capacities C-p,C-phi and apparent molar volumes V-phi w ere determined for aqueous solutions of 1-butanol, 2-butanol (both R and S isomers), isobutanol (2-methyl-1-propanol), and t-butanol (2-methyl-2-propa nol) at temperatures from 278.15 K to 393.15 K and at the pressure 0.35 MPa . The molalities investigated ranged from 0.02 mol . kg(-1) to 0.5 mol . kg (-1). We used a vibrating-tube densimeter (DMA 512P, Anton Paar, Austria) t o determine the densities and volumetric properties. Heat capacities were o btained using a twin fixed-cell, power-compensation, differential-output, t emperature-scanning calorimeter (NanoDSC 6100, Calorimetry Sciences Corpora tion, Provo, UT, U.S.A.). The results were fit by regression to equations t hat describe the surfaces (V-phi, T, m) and (C-p,C-phi, T, m). Infinite dil ution partial molar volumes V-2(o) and heat capacities C-p,2(o) were obtain ed over the range of temperatures by extrapolation of these surfaces to m = 0. (C) 2001 Academic Press.