Korean J. Chem. Eng., 21(5), 1015-1025 (2004) Mixing Properties of Isopropyl Acetate+Aromatic Hydrocarbons at 298.15 K: Density, Refractive Index and Isentropic Compressibility J. M. Resa†, C. Gonzalez, E. Diez, R. G. Concha and M. Iglesias* Dpto. de Ingenieria Química, Universidad del Pais Vasco, Apto. 450, Vitoria, España *Departament d’Enginyeria Química, Escola Tècnica Superior d’Enginyeria Química, Universitat Rovira i Virgili, Avinguda Països Catalans 26, Campus Sescelades, 43007 Tarragona, España (Received 12 December 2003 • accepted 24 June 2004) Abstract−We present new experimental data of density, refractive index and speed of sound for the binaries of isopropyl acetate+(toluene, ethylbenzene, p-xylene, mesitylene, isopropylbenzene, butylbenzene, isobutylbenzene, or t-butylbenzene) at T=298.15 K and standard conditions, and the corresponding computed derived magnitudes (change of isentropic compressibility, change of refractive index on mixing, and excess molar volume). The mixtures show a clear expansive tendency for the highest molar weight compounds and the steric hindrance role of the aromatic chem- icals being analyzed to the light of the non-ideality on mixing. A good agreement among experimental data and the values estimated by theoretical procedures was obtained. Key words: Excess Volumes, Change of Refractive Indices, Change of Isentropic Compressibility, Isopropyl Acetate, Aromatic Hydrocarbon, Prediction INTRODUCTION compounds and the steric hindrance role of the aromatic chemicals being analyzed to explain the non-ideality of mixtures. In what is Many chemical, food and other industries present non-newto- referred to the as the estimation of these magnitudes, different pro- nian and non-ideal fluids and mixtures in their processes. For this cedures were applied: Racket [1970] and modified Racket [Spen- reason, it is necessary to pay attention to the thermodynamic rigor- cer and Danner, 1972] equations for density, mixing rules for re- ous studies and model development to achieve optimal industrial fractive indices and for isentropic compressibilities, the models of designs. This work is a continuation of a wider project in which Danusso [1951] and Nomoto [1958], and the Collision Factor The- the interaction of esters with aromatic hydrocarbons is being inves- ory (CFT) and Free Length Theory (FLT) theories. As a result, an tigated. Isopropyl acetate has good solvency characteristics for res- accurate agreement among the experimental and theoretical values ins, such as cellulosics, vinyl copolymers, polyesters, polystyrene, both in magnitude and sign was obtained. acrylics, kauri and manila gums, rosin, dammar, etc. and is com- monly used in coatings, cleaning fluids, and as a solvent for fra- EXPERIMENTAL SECTION grances, cosmetics and personal care. One of the main uses is in printing inks where fast evaporation and low hygroscopicity are The physical properties of the used chemicals at 298.15 K ap- needed. Other uses include a coalescent in paints, lacquers and coat- pear in Table 1 along with other recent literature values. The chem- ing. Its presence in an aromatic environment is usual and the inter- icals were supplied by Fluka, except isopropyl acetate supplied by actions in mixture are of interest in order to understand and define Panreac, all of them with a purity better than 99.0%. Ultrasonic treat- solubility limits and mechanisms of solvation. ment was used for degassing and also molecular sieves (type 3a, 1/ As a continuation of previous works [Resa et al., 1998, 2001, 16 inch, Fluka) were introduced into the bottles to reduce possible 2002, 2003a, b, c, d], this paper is devoted to the study of different water content in solvents. The mixtures were prepared by mass using thermodynamic properties of mixtures with chemicals containing an ER-182A Salter balance with a precision of ±1.0×10−4 g, spe- the ester group into aromatic environment. To this aim, we present cial care being taken during solution preparation to avoid evapora- experimental data of the binaries of isopropyl acetate+(toluene, ethyl- tion losses. Densities were measured to a precision of ±1.0×10−5 benzene, p-xylene, isopropylbenzene, butylbenzene, isobutylben- g·cm−3 in an Anton Paar DMA 58 digital vibrating tube densitom- zene, mesitylene, or t-butylbenzene) measured at standard conditions. eter. The apparatus was calibrated periodically, in accordance with The speed of sound, refractive index and density on mixing were technical specifications, using Millipore quality water (resistivity, measured and then applied to compute the corresponding derived 18.2 MΩ·cm) and ambient air, as explained in other works [Resa magnitudes, change of isentropic compressibility, change of refrac- et al., 2003a]. Refractive indices were measured with a precision tive index on mixing and excess molar volume which were fitted of ±1.0×10−5 in a Mettler Toledo RE50 refractometer. An Anton to the Redlich-Kister equation [Redlich and Kister, 1948]. The mix- Paar DSA 48 analyzer carried out speed of sound measurements, tures show a rising expansive tendency for increasing molar weight with a precision of ±1.0 m·s−1 and was also frequently calibrated. Maximum deviation in the calculation of excess molar volumes, †To whom correspondence should be addressed. changes of refractive indices on mixing, and changes of isentropic E-mail: [email protected] compresibilities for these mixtures have been estimated better than 1015 1016 J. M. Resa et al. Table 1. Physical properties of the pure solvents at T=298.15 K −1 ρ −3 ρ −3 a a b Compound M/g·mol /g·cm (Expt) /g·cm (Lit.) nD (Expt) nD (Lit.) u (Expt) u (Lit.) Isopropyl Acetate 102.133 0.86622 0.87020 1.37460 1.37500 1103.7 1103.7 Toluene 092.140 0.86216 0.86219 1.49400 1.49413 1305.1 1305.0 Ethylbenzene 106.167 0.86273 0.86253 1.49315 1.49320 1319.0 1319.0 p-Xylene 106.167 0.85660 0.85661 1.49308 1.49325 1309.9 1309.7 Mesitylene 120.194 0.86115 0.86111 1.49675 1.49684 1336.6 1336.8 Isopropylbenzene 120.194 0.85757 0.85743 1.48862 1.48890 1307.9 1307.7 Butylbenzene 134.221 0.85615 0.85607 1.48740 1.48742 1331.7 1334.1 Isobutylbenzene 134.221 0.84898 0.84907 1.48393 1.48400 1296.9 1296.9 t-Butylbenzene 134.221 0.86232 0.86240 1.49011 1.49024 1315.4 1315.6 aOrganic Solvents [1986]. bResa et al., 2003. −3 3 −1 −4 −1 n 2.0×10 cm ·mol , 1.0×10 , and 1.0 TPa , respectively. We are = 1 − xi δκ -------- ∑--------- (3) S 2 2 ρ i = 1ρ not aware of any such data of these mixtures in previous literature, u iui in the studied conditions. ρ In these equations, is the density on mixing, nD the refractive index κ DATA PROCEDURE on mixing and S the isentropic compressibility on mixing. The sym- ρ κ bols i, nDi, ui and Si indicate the properties of pure chemicals and 1. Correlation of Derived Magnitudes n is the number of components in the mixture. A [Redlich and Kister, The excess molar volumes, changes of refractive indices and 1948] type equation was used to correlate the derived properties of changes of isentropic compressibilities on mixing values are presented the binary mixtures, by using the unweighted least squares meth- in Table 2 and were computed from Eqs. (1), (2) and (3): od, all experimental points weighting equally [Marquardt, 1963]. The Redlich-Kister equation can be expressed as: n − − E = 1 − 1 V ∑xiMi()ρ ρi (1) m = p i 1 = − δQ xixj ⋅ ∑Bp()xi xj , (4) p = 0 n δ = − ∑ nD nD xinDi (2) E 3 −1 −1 = δ δ δκ i 1 where Q is V /(cm ·mol ), nD and S/(TPa ), respectively. The Table 2. Thermodynamic properties of isopropyl acetate+(toluene, ethylbenzene, p-xylene, isopropylbenzene, mesitylene, butylbenzene, isobutylbenzene, or t-butylbenzene) at T=298.15 K Isopropyl Acetate+Toluene ρ −3 E 3 −1 δ −1 κ −1 δκ −1 x1 /g·cm V /cm mol nD nD u/(ms ) S/TPa S/TPa 0.0512 0.86262 −0.029 1.48730 −0.0006 1293.9 692.4 −2.2 0.1018 0.86304 −0.054 1.48070 −0.0011 1282.9 704.0 −4.2 0.1500 0.86341 −0.074 1.47447 −0.0016 1272.5 715.3 −5.7 0.1967 0.86374 −0.090 1.46868 −0.0018 1262.5 726.4 −7.1 0.2479 0.86406 −0.104 1.46222 −0.0022 1251.6 738.8 −8.3 0.3056 0.86440 −0.116 1.45504 −0.0025 1239.4 753.2 −9.3 0.3504 0.86463 −0.122 1.44940 −0.0028 1230.0 764.4 −10.00 0.4059 0.86490 −0.128 1.44265 −0.0029 1218.6 778.7 −10.60 0.4498 0.86508 −0.129 1.43733 −0.0030 1209.6 790.1 −10.90 0.5030 0.86528 −0.127 1.43086 −0.0031 1198.8 804.2 −11.00 0.5502 0.86545 −0.125 1.42521 −0.0031 1189.3 816.9 −10.90 0.6009 0.86560 −0.119 1.41933 −0.0029 1179.2 830.8 −10.50 0.6520 0.86574 −0.111 1.41339 −0.0028 1169.2 845.0 −9.9 0.7011 0.86584 −0.099 1.40773 −0.0026 1159.7 858.8 −9.2 0.7488 0.86594 −0.089 1.40230 −0.0023 1150.5 872.4 −8.3 0.8009 0.86603 −0.074 1.39645 −0.0019 1140.6 887.5 −7.1 0.8486 0.86608 −0.057 1.39113 −0.0015 1131.7 901.6 −5.7 0.8990 0.86614 −0.040 1.38561 −0.0010 1122.4 916.5 −4.2 0.9520 0.86618 −0.019 1.37980 −0.0005 1112.6 932.6 −2.4 September, 2004 Mixing Properties of Isopropyl Acetate+Aromatic Hydrocarbons at 298.15 K 1017 Table 2.