Refractometric behavior of ternary liquid mixtures of

Vol. 1 (2017)

KPS – Journal of Physics and Applications

Refractometric behavior of ternary liquid mixtures of cyclohexene, ethanol and acetone at four different temperatures Fisnik ALIAJ1,*, Naim SYLA1, Zeqë TOLAJ1, Arbër ZEQIRAJ1,2, Arlinda BYTYQI-DAMONI3 1) Department of Physics, FMNS, University of Prishtina, Eqrem Cabej Str. 51, KS-10000 Prishtina, Kosovo 2) Department of Materials and Metallurgy, University of Mitrovica, PIM-Trepça, KS-40000 Mitrovica, Kosovo 3) Department of Chemistry, FE, University of Prishtina, Agim Ramadani Str. Nn, KS-10000 Prishtina, Kosovo

Abstract. This paper reports new measurements of refractive indices for the ternary liquid mixtures composed of cyclohexene, ethanol and acetone as a function of composition at four temperatures T = (293.15, 298.15, 303.15 and 308.15) K and atmospheric pressure. Refractive indices for the sodium-D line were measured with a thermostated Abbe’s refractometer that has an overall measurement accuracy of ±0.0002. From the experimental data, the refractive index deviations, which is a quantity closely related to changes in molecular polarizabilities on mixing of component, were calculated at the above-mentioned temperatures. Furthermore, the experimental data were utilized to verify the predictive capacity of traditional mixing rules proposed by Lorentz-Lorenz, Eykman, Edwards, Gladstone-Dale, Eyring-John, Newton and Oster. The predictive capacity was tested by calculating the percentage absolute average deviation (PAAD) between experimental and calculated values. Based on PAAD data, the mixing rule by Eykman has shown the best agreement, while that proposed by Newton has shown the least agreement with experimental data at all temperatures. Keywords: refractive index, mixing rules, thermophysical properties, cyclohexene, ethanol, acetone. Received: 2017-09-25 Accepted: 2017-12-19

1. Introduction Information about thermophysical properties (such as density, viscosity, and refractive index) of pure organic compounds and their mixtures as a function of composition and temperature is important in different industrial applications (Chen and Tu, 2005; Gonzales et al., 2007; Kumar et al., 2014; ; Sheu and Tu, 2006; Vuksanovic et al., 2014). It is necessary for the investigation of non-ideality of mixtures, caused by molecular interactions between the components of the mixture, as well as for the design of processes and process equipment (Vuksanovic et al., 2014). As an extension of our work concerning density and refractive indices of binary (Aliaj et al., 2016a) and ternary liquid mixtures (Aliaj et al., 2016b), in this paper we present experimental refractive indices of ternary mixtures of cyclohexene (x1), ethanol (x2 = 0.4) and acetone (x3) at temperatures from 293.15 to 308.15 K. A literature survey reveals that no refractive index data exists for the mentioned ternary system, the components of which find many applications in industry. Ethanol is a potential clean fuel to substitute for petroleum fuels due to its low emissions, particularly the low level of soot. Acetone is a colorless, mobile, flammable liquid, and is the simplest of ketones. The main application of this compound is as a solvent, also as an intermediate to produce many important chemical substances, and in cosmetics. Cyclohexene is a clear, colorless liquid with a characteristic odor. It is used in oil extraction, to synthesize other chemicals, and as a catalyst solvent.

*

Corresponding author, e-mail: [email protected] (This work is and extended version of the paper published in the Proceedings of the 3 rd Virtual Multidisciplinary Conference QUAESTI2015)

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Experimental data were used to calculate the deviation in refractive index (over the whole composition range), which is a quantity of interest that is closely related to changes in molecular polarizabilities on mixing of component and is considered as a barometer of interaction between the components. Furthermore, seven theoretical and empirical mixing rules were used to predict the refractive indices of the investigated ternary system, and the results were compared with experimental data. The predicting capacity of the mixing rules was tested by calculating the percentage absolute average deviation between experimental and calculated values.

2. Materials and methods The chemicals used were GC grade cyclohexene (C6H10, ≥99.0%, Gatt-Koller), ACS grade ethanol (C2H6O, ≥99.8%, Carlo Erba) and ACS grade acetone (C3H6O, ≥99.5%, Sigma-Aldrich). Ethanol and acetone were used without further purification; Cyclohexene was doubly distilled before use. The purity of the chemicals was checked by measuring their densities and refractive indices at 298.15 K and comparing with literature data. Cyclohexene (1) + ethanol (2) + acetone (3) ternary liquid mixtures of various concentrations in mole fraction were freshly prepared in airtight glass bottles by mixing carefully selected volumes of the pure liquids at ~293 K. Extreme care was taken to minimize the preferential evaporation during mixing and afterward during the measurements. The mole fraction of ethanol was fixed to x2 = 0.4, while mole fractions of other components were varied to cover the whole composition range. There is no specific reason for setting the mole fraction of ethanol to 0.4. Uncertainties in mole fractions were estimated to be less than ±0.0003 for each composition. Refractive indices for the sodium D-line, nD, of the pure liquids as well as of ternary liquid mixtures were measured at T = (293.15, 298.15, 303.15 and 308.15) K and atmospheric pressure with a calibrated Abbe’ refractometer that has an overall measurement accuracy of ±0.0002. The calibration was performed with in-house triple distilled water (1.3330 as its refractive index at 293.15 K), and the readings were verified by using the standard solid sample (type K9) supplied with the apparatus. The temperature of the experimental liquids was controlled, within the limits of ±0.04 K, by circulating water into the prisms of the refractometer using a circulating pump connected to a constant temperature water bath. Densities accurate to ±0.1 kg/m3, measured for the purpose of checking the purity of the chemicals used, were determined with the pycnometer method. The volume of the pycnometer was calibrated with in-house triply distilled water. Before density measurements, the pycnometer filled with experimental liquid was kept for about 30 minutes in a thermostatic water bath maintained at 298.15 ± 0.04 K.

3. Results and discussions A comparison of our measurements of density and refractive index with the data reported in the literature for the pure liquids is shown in Table 1. An excellent agreement was found between experimental values found in our laboratory and those reported in the literature. Relative percent deviation is lower than 0.05% for density measurements and lower than 0.01% for refractive index measurements, showing good accuracy attainable with the methods used in this work.

Refractometric behaviour of ternary liquid mixtures at different temperatures

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Table 1. Refractive indices and densities of the pure liquids, measured in our laboratory and those reported in literature, at 298.15 K and atmospheric pressure. Component

ρ (kg/m3)

nD

Exp.

Lit.

Exp.

Lit.

Cyclohexene

806.5

806.09a

1.4438

1.44377a

Ethanol

784.7

785.08b 785.00c

1.3594

1.3593b 1.35941c

Acetone

784.5

784.4d

1.3558

1.35580d

a. Dreisbach (1959) b. Herraez and Belda (2006) c. Sheu and Tu (2006) d. Iglesias et al. (1998)

Table 2. Refractive indices for the Cyclohexene(1) + Ethanol(2) + Acetone(3) ternary system measured at different temperatures and mole fractions. Mole fraction of ethanol is set to x2 = 0.4. Volume fractions of the pure components are also given. Mole Fractions

Volume Fractions

Refractive index, nD

x1

x3

φ1

φ2

φ3

293.15

298.15

303.15

308.15

0.0 0.1 0.2 0.3 0.4 0.5 0.6

0.6 0.5 0.4 0.3 0.2 0.1 0.0

0.000 0.144 0.278 0.401 0.516 0.623 0.723

0.346 0.332 0.320 0.308 0.297 0.287 0.277

0.654 0.523 0.403 0.291 0.187 0.090 0.000

1.3605 1.3720 1.3825 1.3922 1.4018 1.4113 1.4179

1.3579 1.3694 1.3797 1.3894 1.3991 1.4081 1.4148

1.3553 1.3668 1.3770 1.3867 1.3965 1.4050 1.4120

1.3527 1.3641 1.3742 1.3839 1.3937 1.4021 1.4090

The experimental refractive indices from 293.15 to 308.15 K and various mole fractions for the cyclohexene(1) + ethanol(2) + acetone(3) ternary mixtures are listed in Table 2. Evidently, the refractive index increases with increasing mole fraction of cyclohexene at each investigated temperature, and decreases with increasing temperature at each composition. Initial analysis of the experimental data revealed that the refractive indices can be successfully correlated with a second order polynomial in x1 for each investigated temperature, while the decrease with temperature is always linear. The refractive index deviation, DnD, is a quantity of interest that is closely related to changes in molecular polarizabilities on mixing of component and is also considered as a barometer of interaction between the components. Refractive index deviation has been extensively studied for various binary and ternary liquids mixtures (Bhatia et al., 2001; Chen and Tu, 2005; Crisciu et al., 2014; Herraez and Belda, 2006; Iglesias et al., 1996; Rodriguez et al., 2001; Sharma et al., 2011; Sheu and Tu, 2006). However, as has been pointed out by Brocos et al. (2003), the recent literature displays marked disagreement as to the proper treatment of data on the refractive indices of liquid mixtures. In the literature, the refractive index deviation, which represents the deviation of measured refractive index from ideal behavior, is usually defined on a mole fraction basis, i.e., according to equation

D x n = nexp. - å xi ni i

(1)

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F. Aliaj et al.

Figure 1. Deviations in refractive index for the ternary system C-E-A at indicated temperatures. The solid, dash, dot and dash-dot lines are only guide for the eye.

Here, nexp is the measured refractive index of the mixture; ni and xi are the refractive indices and mole fractions of the pure component liquids, respectively. Dxn is a convenient quantity for reporting highquality data, but it has no physical significance. Dxn does not correlate well with any physically interpretable quantity, like for example with excess molar volume (VE) which is of those excess properties of liquid mixtures that throw light on intermolecular interactions. On the contrary, the refractive index deviation calculated on the volume fraction basis is physically significant, is negatively correlated with VE, and is directly interpretable as a sign-reversed measure of the deviation of reduced free volume from ideality (Brocos et al., 2003). The negative correlation of refractive index deviation (calculated on the volume fraction basis) and excess molar volume was observed in our recent studies on binary liquid mixtures of alcohols with water (Aliaj et al., 2016a) as well as on ternary liquid mixtures of benzene, ethanol, and hexane (Aliaj et al., 2016b). In this study, the refractive index deviation was calculated from the experimental results as suggested by Brocos et al. (2003) on a volume fraction basis, i.e., according to

Dn D = nD,exp. - å ji nD,i .

(2)

i

Here, nD,exp. is the refractive index of the mixture; nD,i and φi are the refractive indices and volume fractions of the pure component liquids, respectively. Graphical variation of DnD (at 293.15 – 308.15 K) as a function of mole fraction of cyclohexene is plotted in Fig. 1. Evidently, DnD is positive for x1 = 0.0, i.e., for the mixture containing no cyclohexene, x2 = 0.4 mole fraction ethanol and x3 = 0.6 mole fraction acetone. The results for this composition are in good agreement with the results by Chen and Tu (2005), who studied, among others, the refractive index deviations in binary mixtures of ethanol and acetone. Replacing acetone molecules (aprotic polar) with cyclohexene molecules (nonpolar) in ethanol environment (x2 = 0.4) makes DnD negative already at x1 = 0.1 mole fraction of cyclohexene, which is indicative of changes in molecular polarizabilities on mixing. By further increasing the mole fraction of cyclohexene makes DnD more negative. The effect of temperature on DnD is more pronounced in the cyclohexene rich region.


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The experimental refractive indices were also compared with the predicted results from the mixing rules proposed by Lorentz and Lorenz (L-L), Eykman (Eyk), Edwards (Edw), Gladstone and Dale (GD), Eyring and John (E-J), Newton (New) and Oster (Ost), which are given as follows (Bhatia et al., 2001; Crisciu et al., 2014; Iglesias et al., 1998; Kumar et al., 2014; Mehra, 2003):

(L-L):

æ n D2 ,i - 1 ö ÷, = å ji ç n D2 ,pred. + 2 i =1 çè n D2 ,i + 2 ÷ø

(3)

(Eyk):

æ n D2 ,i - 1 ö ÷, = å ji ç n D2 ,pred. + 0.4 i =1 çè n D2 ,i + 0.4 ÷ø

(4)

(Edw):

n D2 ,pred. - 1

3

n D2 ,pred. - 1

n D ,pred. - 1 n D ,pred.

3

3 æ n D ,i - 1 ö ÷, = å ji çç ÷ i =1 è n D ,i ø

(5)

3

(G-D):

nD ,pred. - 1 = å ji (nD ,i - 1) ,

(6)

i =1

3

(E-J):

æ 3 ö n D ,pred. = ç å ji n1D3,i ÷ , è i =1 ø

(New):

nD2 ,pred. - 1 = å ji nD2 ,i - 1 ,

3

(

(7)

)

(8)

i =1

(Ost):

(n

2 D ,pred.

)(

)=

- 1 2nD2 ,pred. + 1 n

2 D ,pred.

(

)(

)

é nD2 ,i - 1 2nD2 ,i + 1 ù ji ê ú. å nD2 ,i i =1 êë úû 3

(9)

In eqs. (3) to (9), nD,pred. is the predicted refractive index of the mixture; nD,i and φi are the refractive indices and volume fractions of the pure liquids, respectively. The predicting capacity of the mixing rules was tested by calculating the percentage absolute average deviation (PAAD) between the experimental and predicted refractive indices according to eq. (10)

PAAD (%) =

100 N æç n D ,exp. - n D ,pred. åi=1 ç n N D ,exp. è

ö ÷ . ÷ øi

(10)

In eq. (10), N is the number of experimental data points and exp. and pred. represent the experimental and predicted values, respectively. Graphical variations of PAAD with temperature for the mixing rules (3) to (9) are shown in Fig. 2. Evidently, the mixing rule by Eykman (Eyk) has shown the best agreement with the experimental values at all temperatures, followed by Edward’s (Edw) and Lorentz and Lorenz’s (L-L) mixing rules. The mixing rule by Newton (New) has shown the least agreement with the experimental values. Based on PAAD data, the predicting capacity of the mixing rules follows the sequence Eyk > Edw > L-L > E-J > G-D> Ost > New.

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Figure 2. PAAD between experimental and predicted refractive indices as a function of temperature for the Cyclohexene-Ethanol-Acetone ternary system.

4. Conclusions For the first time, the refractive indices at T = (293.15, 298.15, 303.15 and 308.15) K and atmospheric pressure for the ternary system cyclohexene + ethanol +acetone are reported. From the experimental results, the deviations in refractive index, DnD, were calculated. DnD was positive for the mixture containing no cyclohexene, and became negative already when the mole fraction of cyclohexene was 0.1. DnD increases on an absolute scale with increasing mole fraction of cyclohexene. The refractive indices were compared with the predicted results from seven mixing rules, namely: Lorentz-Lorenz (L-L), Gladstone-Dale (G-D), Eykman (Eyk), Eyring-John (E-J), Edwards (Edw), Newton (New) and Oster (Ost). It can be concluded, based on PAAD data, that the predicting capacity of the mixing rules follow the sequence Eyk > Edw > L-L > E-J > G-D > Ost > New. REFERENCES Aliaj, F., Syla, N., Bytyqi-Damoni, A., 2016a. Refractive indices, densities and excess molar volumes of binary systems methanol+water and ethanol+water at T = 293.15 K. AKTET J. Inst. Alb. Shkenca 9, 36–42. Aliaj, F., Bytyqi-Damoni, A., Syla, N., 2016b. Density and refractive index study of the ternary system benzene-ethanolhexane. In: Akkus¸ B., Oktem, Y., Yalcin, L. S., Mutlu, R. B. C., Dogan, G. S. (eds) AIP Conf. Proc., AIP Publishing LLC, vol.1722, pp 2900151–2900154. Bhatia, S. C., Tripathi, N., Dubey, G. P., 2001. Refractive indices of binary liquid mixtures of squalane with benzene, cyclohexane and hexane at 298.15 to 313.15 K. Indian J. Pure Appl. Phys. 39, 776–780. Brocos, P., Pineiro, A., Bravo, R., Amigo, A., 2003. Refractive indices, molar volumes and molar refractions of binary liquid mixtures: concepts and correlations. Phys. Chem. Chem. Phys. 5, 550–557. Chen, H. W., Tu, C. H., 2005. Densities, viscosities, and refractive indices for binary and ternary mixtures of acetone, ethanol and 2,2,4-trimethylpentane. J. Chem. Eng. Data. 50, 1262–1269. Crisciu, A., Secuianu, C., Feroiu, V., 2014. Densities and refractive indices of 1-hexanol + n-pentadecane binary system at temperatures from (293.15 to 323.15) K. Rev. Chim. Bucharest 65, 76–79. Dreisbach, R. R., 1959. Physical properties of chemical compounds. In: Physical Properties of Chemical Compounds-II, vol. 22, chap. 1, American Chemical Society, Washington, DC, pp 3–486. Gonzales, B., Calvar, N., Gomez, E., Dominguez, A., 2007. Density, dynamic viscosity, and derived properties of binary mixtures of methanol or ethanol with water, ethyl acetate, and methyl acetate at T = (293.15, 298.15, and 303.15) K. J. Chem. Eng. Data 39, 1578–1588.


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