Volumetric study of the ternary liquid mixture (water + ethanol + 1-propanol) at T = 293.15 K and P = 0.1 MPa Luís C.S. Nobre, Ana F. Cristino, Ângela F.S. Santos, Carlos A. Nieto de Castro, Isabel M.S. Lampreia ⇑ Centro de Química Estrutural, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal article info Article history: Received 17 June 2019 Received in revised form 19 August 2019 Accepted 20 August 2019 Available online 21 August 2019 Keywords: Density Aqueous ternary liquid mixture Ethanol 1-Propanol Partial molar volumes Molecular interactions abstract It is well known that alcohol beverages are mainly composed by the two core water and ethanol compo- nents. 1-propanol and 2-propanol, which are the so called ethanol congeners, change the physicochem- ical properties of the binary (water + ethanol) liquid mixture, when present even at small concentration. New accurate density values were obtained for the ternary (water + ethanol + 1-propanol) and binary: (water + ethanol); (water + 1-propanol) and (ethanol + 1-propanol) liquid mixtures, at 293.15 K and 0.1 MPa. Three-dimensional representations of the excess molar and partial molar volumes are presented and interpreted in terms of H-bonding, packing, branching and hydrophobic/hydrophilic balance. The branching effect was assessed by the comparison with the ternary system where 1-propanol is substi- tuted by its bulkier isomer 2-propanol. Ó 2019 Elsevier Ltd. 1. Introduction It is well known that computational simulations, based on pre- dictive equations of state, are widely used to model distillation processes aiming to obtain various alcoholic beverages. Accurate thermodynamic data are required to be used both in the models input data and in the validation of the computer outputs in order to optimize the operation processes [1–4]. Ethanol and water are the main components of the alcoholic liq- uid mixtures to be distilled. The so-called congeners (1-propanol, 1,2-butyl and amyl alcohols, acetaldehyde and some others [5]) present in a much lower concentration, modify the physicochemi- cal properties of the liquid binary mixture {water + ethanol} and must be taken into account. Among the various possible congeners used as flavourings of the final alcoholic product, liquid 1-propanol is the third component in the series of aliphatic alcohols and the most similar to ethanol. Thus the introduction of 1-propanol, with one more CH 2 group than ethanol, as the third component in the binary liquid {water + ethanol} mixture seemed to us interesting to explore. In this work we present a collection of 43 accurate values of experimental density for the liquid ternary mixture (water + etha- nol + 1-propanol), measured at 293.15 K and at atmospheric pres- sure. We found in the literature density data for this same mixture at five different temperatures between (288.15 and 325.15) K and at atmospheric pressure [6], having the authors mainly explored the effect of temperature on the properties of the ternary mixture, leaving to the background the dependency with concentration. In addition to the interest of the current results for thermodynamic databases, the present work presents relevant information on molecular interactions, based on excess molar and excess partial molar volumes, obtained from derivatives of excess molar volumes, adjusted to the Cibulka equation [7]. Pursuing pre- vious works [8–11], where aspects such as H-bonding, branching and hydrophobic /hydrophilic balance were discussed, we compare our results with those estimated for the ternary mixture {water + ethanol + 2-propanol} using data of Ref. [12]. Another important aspect concerns the thermodynamic consis- tency of the results, since new experimental excess molar volumes were obtained for a given number of binary liquid mixtures of the 3 involved components combined two by two. Our new data for the binary mixtures was coupled with date from other authors, where appropriate, in order to obtain reliable values to be com- bined with those of the ternary mixture. 2. Experimental 2.1. Materials and mixtures preparation Liquid ethanol, CAS Registry No. 64-17-5, was obtained from Panreac with purity quoted > 0.999, in mass fraction, and used https://doi.org/10.1016/j.jct.2019.105913 0021-9614/Ó 2019 Elsevier Ltd. ⇑ Corresponding author. E-mail address: milampreia@fc.ul.pt (I.M.S. Lampreia). J. Chem. Thermodynamics 140 (2020) 105913 Contents lists available at ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct