Fluid Phase Equilibria 308 (2011) 78–89 Contents lists available at ScienceDirect Fluid Phase Equilibria j o ur nal homep age: www.elsevier.com/locate/fluid Thermophysical behaviour of the mixture (±)-3,7-dimethyl-1,6-octadien-3-ol with ethanol Sandra M. García-Abarrio, Laura Viloria, Luisa Haya, José S. Urieta, Ana M. Mainar ∗ Group of Applied Thermodynamics and Surfaces (GATHERS), Aragon Institute for Engineering Research (I3A), Universidad de Zaragoza, Facultad de Ciencias, Zaragoza 50009, Spain a r t i c l e i n f o Article history: Received 30 January 2011 Received in revised form 6 June 2011 Accepted 8 June 2011 Available online 14 June 2011 Keywords: PT (±)-Linalool + ethanol mixture Thermophysical properties Cubic EOS SAFT EOS a b s t r a c t This paper reports the experimental values of density, speed of sound and refractive index of binary mixture of (±)-linalool + ethanol at four temperatures in the range of 283.15–328.15 K and 0.1 MPa. Excess molar volume, speed of sound deviation, refractive index deviation, molar refraction, molar refraction deviation and excess isentropic compressibility are also given at the same work conditions. Afterward, prediction of speed of sound and refractive index was carried out using several theoretical models or equations. The experimental density of the binary mixture was measured at high pressure between 20 and 40 MPa in the same range of temperature. Excess molar volume, isobaric thermal expansion, and isothermal compressibility were also calculated. Peng–Robinson (PR), Patel–Teja (PT), the Statistical Associating Fluid Theory (SAFT) and the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) were tested as predictive models of the PT behaviour. The best predictions were obtained with the PC-SAFT equation of state (EOS). © 2011 Elsevier B.V. All rights reserved. 1. Introduction Essential oils from plants have a wide range of applications in several industries such as food, cosmetics and also in pharmaceu- tical preparations. In fact, the last two decades have witnessed an increasing interest for the therapeutic use of natural products as the essential oils [1]. Current investigation about the medical properties of these extracts has revealed their antioxidant, antivi- ral, antimicrobial and anti-inflammatory activities, and then the need to continue investigating [2]. Linalool is a monoterpene often found as the main volatile component of essential oils in several species of medicinal plants, in concrete it is the main component of a chemotype of Lippia alba (Uruguay), that has been success- ful adapted by us to our continental climate [3]. The different chemotypes of plants with high linalool contents are used in tra- ditional medicine to heal several aliments, acute as well as chronic pain [4] and their therapeutic power has been associated with the content of alcohols like linalool itself and its ester linalyl acetate [5]. Linalool possesses a very wide variety of medical properties, Abbreviations: PR, Peng Robinson; PT, Patel–Teja; SAFT, Statistical Association Fluid Theory; PC-SAFT, Perturbed-Chain Statistical Associating Fluid Theory; EOS, equation of state; RK, Redlich–Kister equation; FL, Free Length Theory; CF, Col- lision Factor theory; LL, Lorentz–Lorenz theory; GD, Gladstone–Dale theory; AB, Arago–Biot theory; W, Wiener theory; H, Heller theory; ADD, absolute average percentage deviation. ∗ Corresponding author. Tel.: +34 976 761 195; fax: +34 976 761 202. E-mail address: ammainar@unizar.es (A.M. Mainar). showing anti-inflammatory [6], sedative [7,8], antileishmanial [9] and anticonvulsant activities [10,11], among other. As it has been demonstrated, many factors have great influence in the final com- position of the natural extracts, and thus in their added value. For a given chemotype, the climate [12], the geographical location [13] and the technique of extraction [14,15] are three of the most impor- tant factors to take into account. The common way to obtain these extracts is hydrodistillation and organic solvent extraction, but, sometimes degradation, or solvent contamination, are a risk that cannot to be assumed. For these reasons, supercritical fluids, especially supercritical carbon dioxide (CO 2 ), have been proved as green media and as a very attractive option to implement the extraction and separation of volatile compounds from solid matrices [16]. Supercritical CO 2 usu- ally involves both chemical and economical benefits although its major drawback lying in its non polar character that can lead to poor performance in separation processes of polar compounds. How- ever, this drawback is overcome through the addition of co-solvents or modifiers like light alkanols as ethanol [17]. The optimization of supercritical processes such as extraction or micronization, requires an in-depth knowledge of the thermophys- ical behaviour of the systems concerned. When a co-solvent has to be used, the first step would be to achieve experimental infor- mation, especially about the densities at high pressures of liquid mixtures consisting of a co-solvent (namely, a light alkanol) and a solute of interest [18]. Then, the selection of adequate models to reproduce that experimental thermophysical behaviour, would provide a basis for choosing the operating temperature and pres- 0378-3812/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.fluid.2011.06.011