HUNGAR~JOURNAL OF JNDUSTRIAL CHEMISTRY VESZPREM Vol. 29. pp. 1- 5 (2001) REFRACTIVE INDICES, DENSITIES AND DERIVED EXCESS PROPERTIES OF BINARY AND TERNARY SYSTEMS WITH DIMETHYL SULFOXIDE, WATER AND 1,4-DIOXANE L. M. OMOTA, 0. IUL~ and C. MATEESCU (Department of Applied Physical Chemistry & Electrochemistry, Faculty of Industrial Chemistry, University "POLITEHNICA", 313, Splaiul Independentei, Bucharest, 77206, ROMANIA) Received; August 9, 2000 Refractive indices and densities for binary dimethyl sulfoxide+ water, dimethyl sulfoxide+ 1,4-dioxane systems and ternary dimethyl sulfoxide+water+1,4-dioxane system have been measured at 298.15 K, over the entire mole fraction scale of the mixture. Changes on molar volume, partial molar volume and molar refraction have been calculated. The experimental data were used to test several mixing rules for estimation of the refractive index. Keywords: binary and ternary systems with dimethyl sulfoxide, excess properties Introduction The properties of liquid mixtures have attracted much attention in the literature from both theoretical and practical viewpoints. The properties of dimethyl sulfoxide (DMSO) and its mixtures have been the subject of considerable interest because of its versatility as a solvent and a plasticizer. In addition to our studies on the physico-chemical properties of binary and ternary liquid mixtures containing DMSO, 1,4-dioxane and water {1-4], we report in this paper the measurement of refractive indices for binary DMSO+water, DMS0+1,4-dioxane and ternary DMSO+water+1,4-dioxane mixtures. We present the experimental values of refractive indices and calculated changes of molar refraction on mixing over the entire mole fraction range at 298.15 K and at atmospheric pressure. Moreover, experimental data were used to test several mixing rules for refractive indices. The densities, reported earlier [5], were used here to present the calculated excess molar volumes and excess partial molar volumes. The results are discussed in terms of the molecular interactions between the water and organic molecules. There are less data available concerning the refractive indices for the binary DMSO+water system [6,7]; we mention that refractive indices for the binary DMS0+1,4-dioxane and ternary water+1,4- dioxane+DMSO systems were not found in the literature. Experimental Apparatus and Procedure Refractive indices values for the sodium D-line were measured with a thermostated Abbe refractometer with a precision of± 0.0001. Temperature is accurate to ± 0.05 K. Density of pure liquids and mixtures was measured using a calibrated pycnometer with an internal diameter of 1 mm. An average of duplicate measurements was considered and these are accurate to ± 0.0002 g cm-3• . Materials The used substances were purified by distillation. DMSO was distilled under vacuum of 0.8-0.9 kPa at 338.65 K. The analytical-reagent-grade 1,4-dioxane from Merck was distilled at 374.35 K. The water was bidistillated. The impurities were found by GC. A comparison of refractive index and density values of pure liquids with the literature findings is given in Table 1. The mixtures were prepared favimetrically using a balance with precision of 0.1·10· kg. The experimental uncertainties are: o(XJ = 0.0001, a(p)lkg n{' = 0.2 and o(VSJ!l0-9m3mor1 = 10. 2 Table 1 Densities and refractive indices of pure components at 298.15 K p , w-3-kg m·3 Compound exptl Literature 0.99704&,9 0.9971 Water 0.99705 10 1.0957 1.095378 DMSO 1.0954712 1.0281 1.027978 1,4-dioxane 1.0280213 1.0278314,15 exptl 1.3325 1.4768 1.4198 nv literature 1.3324-'>·11 1.33146 1.33258 1.476812 1.47695 1.47758 1.41945 Table 2 Densities, excess molar volumes and excess partial molar volumes. Binary systems at T= 298.15 K 1.0000 0.9085 0.8287 -0.7585 0.6962 0.6406 0.5205 0.4331 0.3459 0.2979 0.2158 0.1363 0.0782 0.0351 0.0000 1.0000 0.9581 0.8938 0.7829 0.6906 0.5950 0.5459 0.4959 0.3929 0.2861 0.1750 0.0888 0.0470 o.oooo DMSO(l)+WATER(2) 1.0957 0.0000 0.0000 1.0966 -0.2035 0.0267 1.0979 -0.4032 -0.0010 1.0989 -0.5626 -0.0509 1.0997 -0.6938 -0.1310 1.1001 -0.7921 -0.2297 1.0996 -0.9411 -0.5664 1.0973 -0.9826 -0.9415 1.0922 -0.9526 -1.4441 1.0876 -0.9000 -1.7810 1.()756 -0.7466 -2.4697 1.0563 -0.5145 -3.2856 1.0361 -0.3079 -4.0031 1.0166 -0.1406 -4.6136 0.9971 0.0000 -5.1674 DMSO(l)+ 1,4-DIOXANE(2) 1.0957 0.0000 0.0000 1.0934 -O.o708 -0.0115 1.0895 -0.1504 -0.0276 1.0825 -0.2547 -0.0937 1.0764 -0.3074 -0.1755 1.0699 -0.3335 -0.2816 1.0665 -0.3361 -0.3421 1.0630 -0.3313 -0.4066 1.0558 -0.3069 -0.5527 1.0482 -0.2493 -0.7016 1.0403 -0.1650 -0.8520 1.0343 -0.0924 -0.9670 1.0313 -0.0443 -1.0095 1.0281 0.0000 -1.0658 Results and discussion Binary Systems -2.5890 -2.4893 -2.3487 -2.1698 -1.9836 -1.7945 -1.3479 -1.0140 -0.6927 -0.5263 -0.2724 -0.0772 0.0056 0.0221 0.0000 -1.5916 -1.4273 -1.1845 -0.8353 -0.6017 -0.4099 -0.3288 -0.2571 -0.1478 -0.0680 -0.0193 -0.0072 0.0033 0.0000 Tables 2 and 3 list the measured densities ( p ) and refractive indices ( n0 ) together with the calculated values of excess molar volumes ( yE ), excess partial -£-£ molar volumes of the components ( V, , V 2 ) and, respectively. changes of molar refraction on mixing ( M ). Table 3 includes also the results of prediction of Table 3 Refractive indices, changes of molar refraction on mixing and refractive indices deviations calculated with several mixing rules. Binary systems at T=298.15 K 1.0000 0.9085 0.8287 0.7585 0.6962 0.6406 0.5205 0.4331 0.3459 0.2979 0.2158 0.1363 0.0782 0.0351 0.0000 1.0000 0.9581 0.8938 0.7829 0.6906 0.5950 0.5459 0.4959 0.3929 0.2861 0.1750 0.0888 0.0470 0.0000 L!R, 10·6 Linv nv m3mor1 L-L G-D A-B EDW DMS0(1)+WATER(2) 1.4768 0.0000 0.0000 0.0000 0.0000 0.0000 1.4739 -0.0272 -0.0008 -0.0008 -0.0038 -0.0011 1.4713 -0.0474 -0.0015 -0.0014 -0.0079 -0.0021 1.4685 -0.0661 -0.0022 -0.0020 -0.0118 -0.0031 1.4658 -0.0767 -0.0028 -0.0025 -0.0152 -0.0038 1.4630 -0.0833 -0.0032 -0.0029 -0.0183 -0.0044 1.4552 -0.0915 -0.0040 -0.0037 -0.0246 -0.0056 1.4475 -0.0892 -0.0043 -0.0041 -0.0285 -0.0060 1.4371 -0.0821 -0.0044 -0.0044 -0.0312 -0.0060 1.4298 -0.0754 -0.0044 -0.0045 -0.0317 -0.0058 1.4135 -0.0634 -0.0042 -0.0046 -0,0305 -0.0051 1.3914 -0.0494 -0.0037 -0.0044 -0.0251 -0.0040 1.3701 -0.0352 -0.0029 -0.0037 -0.0177 -0.0028 1.3505 -0.0225 -0.0020 -0.0026 -0.0096 -0 .. 0018 1.3325 0.0000 0.0000 0.0000 0.0000 o:oooo DMS0(1)+ 1,4-DIOXANE(2) 1.4768 0.0000 0.0000 0.0000 0.0000 0.0000 . 1.4741 -0.0124 -0.0003 -0.0003 -0.0013 -0.0004 1.4698 -0.0324 -0.0009 -0.0008 -0.0029 -0.0011 1.4628 -0.0519 -0.0014 -0.0013 -0.0048 -0.0016 1.4572 -0.0593 -0.0015 -0.0015 -0.0056 -0.0018 1.4515 -0.0641 -0.0016 -0.0016 -0.0059 -0.0019 1.4487 -0.0619 -0.0015 -0.0015 -0.0059 -0.0019 1.4458 -0.0621 -0.0015 -0.0015 -0.0058 -0.0018 1.4401 -0.0549 -0.0013 -0.0013 -0.0052 -0.0016 1.4343 -0.0449 -0.0011 -0.0011 -0.0041 -0.0012 1.4284 -0.0337 -0.0008 -0.0008 -0.0028 -0.0009 1.4241 -0.0188 -0.0004 -0.0004 -0.0015 -0.0005 1.4220 -0.0113 -0.0003 -0.0003 -0.0008 -0.0003 1.4198 0.0000 0.0000 0.0000 0.0000 0.0000 refractive indices by various mixing rules: Lorentz- Lorenz (L-L), Gladstone-Dale (G-D), Arago-Biot (A- B), Edwards (EDW). The deviations between experimental and predicted values of the refractive indices were represented by 1m . Excess molar volumes and changes of molar refraction on mixing were calculated from: · VE = 'L.X;M;~-l-Pt) (1) M=R- LX1R1 (2) R=V n~-1 n~+2 (3) where X 1 is the mole fraction of component i; p and R are the density and molar refraction of the mixture, respectively; M 1 , p1° and R1 are the molar mass, density and molar refraction of pure components. The molar refractions were calculated from the Lorentz- Lorenz equation (eq.3), Vbeing the molar volume. ve and AR for the binary systems were fitted with Redlich-Kister polynomials [16J to derive the binary coefficients, Ak, and standard deviation, n, between the observed and calculated quantities: 3 Table 4 Coefficients and standard deviations for excess molar volumes and changes of molar refraction on mixing. Binary systems at T=29S.15 K DMSO+water DMSO+ 1,4-DIOXANE DMSO+WATER+ + 1,4-DIOXANE Coefficients vE, vE, vE, M, M, M., 10'6m3mor1 10'6m3mor1 10. 6m3mor1 10·6m3mor 1 10· 6m3mor1 10.6m3mor1 AO -3.8264 -0.3679 Al 1.3438 -0.0305 A2 0.1426 0.0815 A3 -0.3202 0.1833 A4 0.7828 -0.2069 A5 A6 A7 AS A9 cr, 10'6m3mor1 0.0013 0.0013 -0.20 + DMSO+water ,.. DMS0+1,4-dioxane -1.00 -1.20 +----.---~----.----~-------1 0.00 0.20 0.40 0.60 0.80 1.00 x, a) 1.00.--------------------, - DMSO+water ~ DMS0+1,4-dioxane -0.00 +-----.---~~--...,-------,.----! o.oo 0.20 o.4o o.ro 0.80 1.00 x, b) Fig.l Excess molar volume (a) and excess partial molar volume (b) vs. mole fraction of DMSO. Binary systems at T=298.l5K. -1.3339 -0.2449 -0.2614 -0.0821 0.0079 -0.0611 0.0015 0.0366 -0.0746 -0.1443 0.0024 0.0009 1.4a 1.46 1.44 1 .$ 1.42 ~ ! 1.40 1.38 1.36 1.34 -22.8351 -7.7350 -2.3061 5.4136 -39.8483 -20.1031 -69.6860 -84.2652 -74.7347 4.6162 0.0945 -1.9693 -0.4168 -2.0049 2.8996 -2.3964 -2.9990 -5.1973 0.0186 -O.o1 -002 ;, a ·C03 ~ -0.09 1.32 +---~--~----.---------+..010 0.00 0.20 0.40 x, 0.60 0 60 1.00 Fig.2 Refractive indices and changes of molar refraction on mixing vs. mole fraction ofDMSO. Binary systems at T=298.15K. Z=X;XiLAk(2X; -lr-1 k (4) (5} where Z represents the experimental and calculated excess values (vE' or ilR). Nexp is the number of experimental data and Npar is the number of parameters. No significant better standard deviation was obtained by trying various models to correlate the excess values. The parameters of the fitting equation (4) and the corresponding standard deviations are presented in Table4. We have also calculated excess partial molar -E volumes, V; , as follows: (6) 4 Table 5 Refractive indices, changes of molar refraction on mixing and refractive indices deviations calculated with several mixing rules. Ternary system at T=298.15 K x1 Xz p 103, LlR 106, Llnv k ni3 nv m3mor1 L-L G-D A-B EDW 0.0999 0.8001 1.0376 1.4242 -0.0208 -0.0005 -0.0004 -0.0043 -0.0008 0.1000 0.5998 1.0535 1.4358 -0.0433 -0.0011 -0.0010 -0.0075 -0.0016 0.0998 0.4001 1.0691 1.4480 -0.0548 -0.0015 -0.0014 -0.0091 -0.0021 0.1000 0.1999 1.0838 1.4602 -0.0686 -0.0020 -0.0018 -0.0088 -0.0026 0.1997 o.6000 1.0490 1.4300 -0.0238 -0.0007 -0.0005 -0.0088 -0.0013 0.1998 0.4020 1.0662 1.4420 -0.0721 -0.0021 -0.0019 -0.0123 -0.0029 0.2000 0.2001 1.0835 1.4572 -0.0371 -0.0011 -0.0009 -0.0118 -0.0021 0.1998 0.1000 1.0927 1.4632 -0.0876 -0.0028 -0.0025 -0.0136 -0.0038 0.3002 0.5999 1.0442 1.4220 -0.0518 -0.0016 -0.0013 -0.0121 -0.0025 0.3000 OAOOO 1.0627 1.4364 -0.0459 -0.0015 -0.0012 -0.0143 -0.0025 0.3000 0.2000 1.0835 1.4508 -0.0947 -0.0032 -0.0028 -0.0187 -0.0046 0.2999 0.1002 1.0918 1.4582 -0.0908 -0.0032 -0.0028 -0.0175 -0.0044 0.3997 0.5001 1.0465 1.4200 -0.0526 -0.0018 -0.0015 -0.0149 -0.0028 0.4000 0.4002 1.0573 1.4275 -0.0659 -0.0023 -0.0020 -0.0173 -0.0035 0.4002 0.1998 1.0812 1.4436 -0.1085 -0.0040 -0.0036 -0.0233 -0.0057 0.3998 0.1002 1.0911 1.4522 -0.0979 -0.0038 -0.0034 -0.0226 -0.0054 0.5000 0.4001 1.0503 1.4170 -0.0744 -0.0028 -0.0025 -0.0201 -0.0042 0.5001 0.3000 1.0629 1.4256 -0.0863 -0.0034 -0.0031 -0.0231 -0.0049 0.5002 0.1998 1.0751 1.4348 -0.0850 -0.0035 .{).0032 -0.0246 -0.0051 0.4998 0.1002 1.0884 1.4440 -0.1030 -0.0044 -0.0040 -0.0272 -0.0062 0.5997 0.3002 1.0528 1.4130 -0.0728 -0.0032 -0.0029 -0.0236 -0.0047 0.6001 0.1997 1.0685 1.4232 -0.0857 -0.0039 -0.0036 -0.0281 -0.0057 0.6000 0.1000 1.0826 1.4352 -0.0529 -0.0025 -0.0023 -0.0282 -0.0044 0.7000 0.2001 1.0564 1.4082 -0.0582 -0.0030 -0.0027 -0.0278 -0.0047 0.6998 0.1000 1.0734 1.4200 -0.0590 -0.0032 -0.0030 -0.0310 -0.0050 0.8001 0.1500 1.0466 1.3928 -0.0388 -0.0024 -0.0022 -0.0269 -0.0039 0.7990 0.0500 1.0645 1.4042 -0.0569 -0.0037 -0.0039 -0.0299 -0.0049 0.9000 0.0500 1.0366 1.3732 -0.0377 -0.0029 -0.0031 -0.0223 -0.0036 0.9000 0.0250 1.0407 1.3765 -0.0331 -0.0026 -0.0031 -0.0213 -0.0030 where V; represents the partial molar volumes and '1';0 the molar volumes of the pure components. The curves of excess molar volumes (eq.l), of excess partial molar volumes and of changes of molar refraction on mixing (eq.2) are given in Figs. I and 2; Fig.2 contants also the refractive index as function of mole fraction. The values of V E are negative for both binary systems, the magnitude of minimum value of Ve observed in the case of DMSO+water is approximately three times larger than that observed in DMSO+l.4-dioxane mixture. The excess partial molar volumes of components are mostly negative and decrease with Xi, for· both systems. Negative excess volumes are characteristic of polar nonelectrolyte mixtures. intermolecular interactions. The main effect in DMSO+water system is the strong H-bonding between DMSO and water, reflected by the negative values of V:. Smaller negative values of yE for DMS0+1,4- dioxane are due to unlike dipole-dipole interactions between SO groups of DMSO and 0 group of 1,4- dioxane. The addition of 1,4-dioxane (dipole moment p = 0.4 D) to the DMSO (p = 4.06 D) tends to destroy the strong polar type interaction between DMSO molecules. The negative M values for binary systems vary almost identically throughout the composition scale with the values of y£. The ilR for DMSO+water system is greater than AR for DMSO+l,4-dioxane -E: system. More negative v.e. v, and AR observed for DMSO+water mixture compared to those for DMSO+ t4·dioxane is supported by the published results refering to 11£ and GE of the mixtures {2-4}. E -£ Negative values of V , V, and .:JR suggest the presence of specific interactions between the mixing components. Because of three distinctive functional ~ps. DMSO is capable to exhibit intra and Our studies agree with other studies in the literature [6] for DMSO+water system. Several methods to predict refractive indices of mixtures were applied to test their validity in high polar mixtures. The refractive indices were predicted by mixing rules proposed in literature [17,18]. The results are presented in Table 3. It can be seen from this Table that for these binary systems, the Lorentz-Lorenz mixing rule was the most suitable; the Arago-Biot mixing rule gave in both cases poor predictions of the refractive index. A close similarity was observed between the Lorentz-Lorenz and Gladstone-Dale relations. Ternary Systems Experimental densities, refractive indices and changes of molar refraction of mixing are given in Table 5. Excess molar volumes and changes of molar refraction of mixing were fitted using equation (7): z = X 1XzXJAo +A1(x1- X 2 )+Az(xl -X3)+ +A3 (X 2 -X3 )+A.,(X1 -X2 Y +A5 (x 1 -X3 Y + (7) +A6 (X 2 -X3 Y + ..... ] where Z represents V' or L1R. The results of fitting equation (7), parameters and standard deviations, are given in Table 4. The values of AR are negative over the entire composition range. The binary mixtures DMSO+water, DMS0+1,4-dioxane present negative AR values with a minimum of -0.09 cm3mor1 and -0.064 cm3mol'\ respectively. The AR values of ternary system are also negative with a minimum of- 0.136 cm3mor1• The values of ternary V', reported previously [5], are likewise negative for all compositions. The predictive mixing rules for the refractive indices were used. The differencies between the experimental and calculated values (Ann in Table 5) show that the better results were obtained by Lorentz-Lorenz and Gladstone-Dale equations. Conclusion Excess values of molar volumes, partial molar volumes and molar refraction supported by earlier reported properties indicate the presence· of molecular interactions in binary and ternary studied systems. Lorentz-Lorenz and Gladstone-Dale mixing rules for refractive indices lead to the best results. Acknowledgements This work was financed by CNCSIS (National Council . for Academic Scientific Research ROMANIA) grant. SYMBOLS Ak coefficients in Redlich-Kister equation GE excess Gibbs free energy k degree of the Redlich-Kister polynomials Mt molar mass of component i Nexp number of experimental points Npar number of parameters in Redlich-Kister equation nv refractive index R; molar refractivity of component i R molar refractivity of mixture AR changes of molar refractivity on mixing ¥;0 molar volume of the pure components i vE excess molar volume V. partial molar volume of component i -E V; v X; z excess partial molar volume of component i molar volume of mixture mole fraction of component i 5 experimental and calculated excess values for V' orAR Greek Letters P? density of pure component i p density of mixture · 1JE excess viscosity J-l dipole moment a standard deviation REFERENCES 1. 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