Fluid Phase Equilibria 367 (2014) 85–94 Contents lists available at ScienceDirect Fluid Phase Equilibria jou rn al h om epage: www.elsevier.com/locate/fluid Viscosity and density measurements of compressed liquid dimethyl adipate using oscillating body techniques João C.F. Diogo, Fernando J.P. Caetano 1 , João M.N.A. Fareleira ∗ Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal a r t i c l e i n f o Article history: Received 12 September 2013 Received in revised form 6 January 2014 Accepted 23 January 2014 Available online 31 January 2014 Keywords: Viscosity Density Vibrating wire High pressure Dimethyl adipate a b s t r a c t The article reports viscosity measurements of compressed liquid dimethyl adipate obtained with a vibrat- ing wire sensor. The vibrating wire instrument was operated in the forced, or steady-state, mode of oscillation. The viscosity measurements were carried out up to 20 MPa and at temperatures from (293 to 358) K. The required density of the liquid sample was obtained using a vibrating U-tube densimeter, model DMA HP, from Anton Paar GmbH. The measurements were performed in the temperature range (293–358) K and at pressures up to 25 MPa. The viscosity results were correlated with density, using a modified hard-spheres scheme. The root mean square deviation of the data from the correlation is less than 0.2%. The expanded uncertainty of the present viscosity results is estimated as ±1% at a 95% confidence level. Independent viscosity measurements were performed, at atmospheric pressure, using an Ubbelohde capillary in order to compare with the vibrating wire results, extrapolated by means of the above men- tioned correlation. The two data sets agree within ±0.6%, well within the mutual uncertainty of the experimental methods. No literature data could be found for the viscosity of dimethyl adipate at pressures above 0.1 MPa. As a consequence, the present viscosity results could only be compared upon extrapola- tion of the vibrating wire data to 0.1 MPa. The present extrapolated vibrating-wire results have a good agreement with the literature data at temperatures around 293 K. However, the absolute deviations of the literature results increase steadily with increasing temperature up to around +0.04 mPa s or +2.0%. For higher temperatures up to 358 K the absolute deviations are nearly constant, around +0.05 mPa s. The maximum relative deviation to literature data in the whole range of the present viscosity measurements was +4.2% at 358 K. The density results obtained in the present work agree with the literature data within ±0.1% in the temperature and pressure ranges of the measurements. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Adipates are claimed to be “green” solvents for a wide range of applications in the chemical and polymer, industries. They are used as solvents, plasticizers, lubricants, hydraulic fluids, gear and automotive engine oils, low temperature greases and fuel additives [1–10]. They are stable, have low toxicity, low vapour pressure and are commercially available at reasonably low cost [1–10]. As plasticizers they are alternatives to some phthalates [4,5,8], which may possibly have undesirable effects [3,8]. As novel Abbreviations: HFC, hydrofluorocarbons; KF, Karl-Fischer; NMR, nuclear magnetic resonance; PTB, Physikalisch-Technische Bundesanstalt; PTFE, polite- trafluoroethylene; SI, International System of Units. ∗ Corresponding author. Tel.: +351 218419265. E-mail address: j.fareleira@ist.utl.pt (J.M.N.A. Fareleira). 1 Address: Universidade Aberta, R. da Escola Politécnica, 147, 1269-001 Lisbon, Portugal. solvents, they have the potential to replace conventional organic solvents [11], with high volatility and high toxicity [3,7]. Diesters with small chain substitutes, like dimethyl adipate, have viscos- ity and density close to those of water. As fuel additives they can be injected directly on automotive engines and simultaneously decrease both NO x and smoke emissions [3,6,12]. Applications of these liquids in industrial processes require the knowledge of their thermophysical properties, like viscosity and density. Recently, simultaneous measurements of viscosity and density of compressed liquid diethyl adipate were obtained with a vibrating wire technique by Meng et al. [10]. Comu ˜ nas et al. [2], published density data of compressed liquid dimethyl, diethyl and diisobutyl adipates, using an Anton Paar DMA HPM densimeter. The latter authors have also reported viscosity measurements of the same adipates [2], at atmospheric pressure, obtained with an Anton Paar Stabinger SVM 3000 viscometer. Notwithstanding the numerous potential applications of dimethyl adipate, no viscosity data have been found in the literature for pressures above 0.1 MPa. In the present work measurements of 0378-3812/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fluid.2014.01.030