Scientific paper Viscosity ^-Coefficient for Sodium Chloride in Aqueous Mixtures of 1,4-Dioxane at Different Temperatures Renato Toma{,1* Toni Jovanovi}1 and Marija Be{ter-Roga~2 1 Faculty of Chemistry and Technology, University of Split, Nikole Tesle 10, HR-21000 Split, Croatia. 2 Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ve~na pot 113, SI-1000 Ljubljana, Slovenia. * Corresponding author: E-mail: rtomas@ktf-split.hr Received: 19-02-2015 Dedicated to prof. Jože Koller on the occasion of his 70th birthday. Abstract Viscosities of sodium chloride solutions in water-1,4-dioxane binary mixtures with mole fractions of 1,4-dioxane, xD = 0.05, 0.10, 0.15 and 0.20, in the temperature range from 278.15 to 318.15 K were determined. The relative viscosity data have been analyzed and interpreted in terms of the rearranged Jones-Dole equation, (nr- 1) - Ac1'2 = Bc. The viscosity A-coefficients were calculated from Falkenhagen and Vernon theory by help of the literature limiting ionic conductivity data and B-coefficients were estimated from linear plots. All B-coefficients obtained for NaCl water-1,4-dioxane binary mixtures are positive at all temperatures. These data were compared with the data for NaCl in aqueous medium at different temperatures reported in literature. The ion-ion, ion-solvent and solvent -solvent interactions have been discussed. Keywords: Sodium chloride, water-1,4-dioxane binary mixtures, viscosity data, viscosity B-coefficient, ions-solvent interactions 1. Introduction Viscometric studies of electrolyte solutions have been often used in order to obtain information regarding solute-solvent interactions. Whereas viscosity of electrolyte solutions has been widely studied in water and organic solvents,1'2 less consideration has been devoted to solutions in solvent mixtures. A survey of the literature on the viscosity data of electrolytes solutions in aqueous mixtures with organic solvents shows that they were determined mostly for 1,1 type of electrolytes and usually at one or only several temperatures in aqueous mixtures of formamide,3,4 N,N-dimethylformamide,5 dimethylsulfoxi-de,6 acetone,7 dimethylacetamide,8 2-ethoxyethanol,9 methanol,1011 ethylene glycol1213 and tert-butanol.14 Among aqueous mixtures water-1,4-dioxane mixtures permit the widest variation of the solvent permittivity ranging from 2.21 to 78.36 in pure 1,4-dioxane and in water at 298.15 K, respectively.15 Thus, these mixtures have been used as a favourite solvent system to study ion-ion, solvent-ion and solvent-solvent interaction.16-19 Surpri- singly, there is a lack of the viscometric studies of electrolyte solutions in these mixtures. To our best knowledge there are only two investigation dealing with viscosity of electrolytes in water-1,4-dioxane mixtures. In 1973 Fuoss and Reynolds reported viscosity data for alkali metal hali-des and tetraalkylammonium salts in water-1,4-dioxane mixtures containing 0-63 mass % of 1,4-dioxane at 298.15 K.20 Das and Das investigated viscosities of NaCI, NaBr, NaNO3, KCI, KBr and KNO3 solutions in water-1,4-dio-xane mixtures with 10, 20 and 30 mass % of 1.4-dioxane, and at four ranging from 303.15 to 328.15 K.21 Unfortunately in this paper no experimental data are given. In the present work precise viscometric data for Na-Cl in water-1,4-dioxane binary mixtures (with mole fraction of 1,4-dioxane, xD = 0.05, 0.10, 0.15, and 0.20) in the concentration range 0.05 < c/ moldm-3< 0.30 at nine temperatures (from 278.15 to 318.15 K in step of 5 K) are reported. The relative viscosity data, nr, have been analysed and interpreted in terms of the rearranged Jones-Dole equation, (nr - 1) - Ac1/2 = Bc. From the reported limiting ionic conductivity data,16,17 the viscosity A-coefficients have been calculated from Falkenhagen and Vernon theory.2'22 Viscosity B-coefficient were determined, compared with those reported for NaCl in water2 and in water-1,4-dioxane mixtures at 298.15 K20 and discussed in terms of ion-solvent interactions. rature (± 0.005 K) by the method of Kratky et al.25 using Anton Paar density meter DMA 5000 (Anton Paar, Graz, Austria) with a declared reproducibility ~5 x 10-3 kg m-3. The errors from calibration and temperature control yield an uncertainty of 0.05% of absolute viscosity. 2. Experimental 3. Results and Discussion 2. 1. Materials 1'4-dioxane (Merck, p.a.) was used without further purification. Demineralized water was bi-distilled in a quartz apparatus (DESTAMAT Bi18E, Heraeus). The final product with a specific conductivity of less than 0.5 ^S cm-1 was applied. Sodium chloride (NaCl, Merck, p.a., >99.5%) was dried before use at 130 °C for 24 h. The mixed solvents were prepared by weighing and stock solutions were prepared by adding of weighed amount of solvent to weighed amount of NaCl. Solutions of definite molality were prepared by weighing the pure mixed solvent and the stock solution of NaCl in a particular mixed solvent. The molarity, c can be determined from the mola-lity and density data by means of the relation: (1) where m is the molality of solution (moles of electrolyte per kilogram of solvent), p is the density of solution, and M is the molar mass of sodium chloride. Taking into account the sources of errors (impurities, weighing, ...), concentrations c are accurate ± 0.0001 mol dm 3. 2. 2. Viscosity and Density Measurements The viscosites of solutions were determined with a micro Ubbelohde viscometer (SI Analytics GmbH, Mainz, Germany, type and capillary no. 53610/I) and an automatic flow time measuring system ViscoSystem® AVS 370. The viscometer was immersed in a transparent thermostat bath with the precision of the set temperature better than 0.01 K. Each measurement was automatically repeated at least five times and yielded a reproducibility of the flow time of better than 0.02 %. The kinematic viscosity of solutions, v (m2 s-1), was calculated from the equation23 v = C ■ t - E/t2, where t (s) is the flow time, C and E are constants characteristic for the viscometer and were determined by calibration of the viscometer with water. The values of C = 1.00772 x 10-8 m2 s-2 and E = -4.9602 x 10-5 m2 s were determined by using the kinematic viscosity of water (v(293.15 K) = 1.0038 x 10-6 m2 s-1 and v (298.15 K) = 0.8929 x 10-6 m2 s-1))24 and the flow times at 293.15 K and 298.15 K. The absolute (dynamic) viscosity, n (Pa s = kg m-1 s-1), was obtained from the relation, n = v p, where p (kg m 3) is the density of investigated solution, which was determined at each tempe- The measured viscosity, n, and density, p, data for the solutions of NaCl at all operating temperatures in wa-ter-1,4-dioxane binary mixtures with mole fraction of dioxane, xD = 0.05, 0.10, 0.15, and 0.20 are presented in Tables 1-4, and in Figures S1 - S4 in Supporting information. It is evident that density and viscosity continually increase with increasing concentration of NaCl and increasing content of 1,4-dioxane in the mixture and decreases with increasing temperature in all investigated systems. A comparison between densities, p0, and viscosities, n0, of the solvent mixtures as determined in our work and the literature data162627 at 293. 15 and 303.15 K shows an excellent agreement (Figure S5 in Supporting information). The relative viscosity, nr, of electrolyte solution is related to the molarity, c, according to the Jones-Dole equation: ~ ~ I+ + Be (2) where n and n0 are the viscosities of the solution and solvent, respectively. Eq. (1) in this form, is used by the most of authors for processing viscosity data.22,28 At higher concentration (c > 0.5 mol dm 3) a quadratic term Dc2 is added in eq. (2) and that expression is known as Ka-minsky relation.29 Viscosity coefficients A, B, and D depend on the solute, the solvent, and the temperature. The viscosity A-coefficient is a measure of long-range ion-ion interactions, and the viscosity B-coefficient depends on ion-solvent interactions.2 30 The A and B coefficients can be obtained from the intercept and the slope of the straight line using Eq. (2) in the next form (j/r-l )-A-cm = Be (3) Thus determined A-values should be positive, while B-values can be positive or negative. Furthermore, if the limiting molar conductivities of the constituent ions are known, A-value can be calculated theoretically from the ionic interaction theory by Falkenhagen and Vernon2,22 by help of the relation28 (4) where er is relative permittivity of the solvent and Л°°\ Я+°, and Я™' are limiting molar conductivities of the electrolyte, cation, and anion respectively, at temperature T. Table 1. Experimental densities, p, and viscosities, n, as function of concentration, c, of NaCl solution in water-1,4-dioxane mixtures with mole fraction of 1,4- dioxane, xD = 0.05 at different temperatures. c / mol dm 3 p/ g cm 3 n / mPa s c / mol dm 3 p/ g cm 3 n / mPa s c / mol dm 3 p/ g cm 3 n / mPa s T = 278.15 K T = 293.15 K T = 308.15 K 0 1.022388 2.3061 0 1.016686 1.4614 0 1.009405 1.0144 0.0511 1.024616 2.3238 0.0508 1.018802 1.4783 0.0504 1.011565 1.0234 0.1021 1.026697 2.3438 0.1015 1.020837 1.4895 0.1008 1.013606 1.0325 0.1530 1.028743 2.3577 0.1521 1.022884 1.4990 0.1510 1.015502 1.0407 0.2038 1.030942 2.3689 0.2026 1.024967 1.5092 0.2012 1.017606 1.0468 0.2545 1.032731 2.3798 0.2531 1.027012 1.5174 0.2512 1.019622 1.0531 0.3052 1.035021 2.4047 0.3034 1.028953 1.5313 0.3012 1.021537 1.0627 T = 283.15 K T = 298.15 K T= 313.15 K 0 1.020564 1.9555 0 1.014426 1.2848 0 1.006727 0.9131 0.0510 1.022863 1.9799 0.0507 1.016517 1.2971 0.0503 1.008864 0.9207 0.1019 1.024991 1.9921 0.1013 1.018598 1.3026 0.1005 1.010911 0.9297 0.1527 1.027038 2.0046 0.1518 1.020603 1.3153 0.1506 1.012804 0.9355 0.2034 1.029094 2.0156 0.2022 1.022659 1.3216 0.2006 1.014897 0.9400 0.2540 1.031001 2.0252 0.2525 1.024688 1.3335 0.2506 1.016902 0.9484 0.3046 1.033217 2.0433 0.3027 1.026653 1.3369 0.3004 1.018806 0.9554 T = 288.15 K T = 303.15 K T= 318.15 K 0 1.018775 1.6845 0 1.011946 1.1262 0 1.003919 0.8249 0.0509 1.020893 1.7031 0.0506 1.014158 1.1398 0.0502 1.005910 0.8297 0.1017 1.022998 1.7134 0.1010 1.016174 1.1501 0.1002 1.008089 0.8382 0.1524 1.025043 1.7242 0.1514 1.018116 1.1599 0.1502 1.009981 0.8440 0.2031 1.027130 1.7339 0.2017 1.020186 1.1640 0.2001 1.012063 0.8512 0.2536 1.029192 1.7449 0.2519 1.022259 1.1727 0.2499 1.014060 0.8583 0.3040 1.031190 1.7596 0.3020 1.024156 1.1847 0.2995 1.015851 0.8627 Table 2. Experimental densities, p, and viscosities, n, as function of concentration, c, of NaCl solution in water-1,4-dioxane mixtures with mole fraction of 1,4- dioxane, xD = 0.10 at different temperatures. c / mol dm 3 p/ g cm 3 n / mPa s c / mol dm 3 p/ g cm 3 n / mPa s c / mol dm 3 p/ g cm 3 n / mPa s T = 278.15 K T = 293.15 K T = 308.15 K 0 1.036924 2.9318 0 1.028437 1.8370 0 1.019026 1.2476 0.0511 1.039070 2.9642 0.0507 1.030495 1.8539 0.0502 1.021071 1.2641 0.1023 1.041146 2.9823 0.1014 1.032545 1.8703 0.1005 1.023104 1.2771 0.1538 1.043129 3.0018 0.1525 1.034507 1.8814 0.1511 1.025053 1.2828 0.2054 1.045281 3.0288 0.2037 1.036616 1.8963 0.2019 1.027136 1.2991 0.2573 1.047019 3.0554 0.2552 1.038364 1.9189 0.2528 1.028901 1.3112 0.3094 1.049527 3.0873 0.3069 1.040800 1.9395 0.3041 1.031284 1.3189 T = 283.15 K T = 298.15 K T= 313.15 K 0 1.034227 2.4840 0 1.025398 1.6018 0 1.015692 1.1152 0.0509 1.036303 2.5095 0.0505 1.027450 1.6202 0.0500 1.017737 1.1320 0.1020 1.038374 2.5252 0.1011 1.029495 1.6342 0.1002 1.019766 1.1430 0.1534 1.040348 2.5470 0.1521 1.031450 1.6430 0.1506 1.021713 1.1513 0.2049 1.042483 2.5670 0.2031 1.033548 1.6604 0.2012 1.023790 1.1622 0.2566 1.044226 2.5871 0.2544 1.035301 1.6837 0.2520 1.025561 1.1697 0.3086 1.046706 2.6164 0.3060 1.037716 1.7030 0.3031 1.027932 1.1847 T = 288.15 K T = 303.15 K T= 318.15 K 0 1.031380 2.1268 0 1.022261 1.4067 0 1.012259 1.0037 0.0508 1.033445 2.1453 0.0504 1.024309 1.4209 0.0499 1.014306 1.0142 0.1017 1.035506 2.1620 0.1008 1.026347 1.4305 0.0998 1.016334 1.0309 0.1529 1.037474 2.1738 0.1516 1.028299 1.4404 0.1501 1.018279 1.0376 0.2043 1.039595 2.1995 0.2025 1.030389 1.4595 0.2005 1.020354 1.0481 0.2559 1.041388 2.2155 0.2536 1.032146 1.4756 0.2512 1.022129 1.0539 0.3077 1.043795 2.2406 0.3050 1.034545 1.4932 0.3021 1.024490 1.0676 Table 3. Experimental densities, p, and viscosities, n, as function of concentration, c of NaCl solution in water-1,4-dioxane mixtures with mole fraction of 1,4- dioxane, xD = 0.15 at different temperature. c / mol dm 3 p/g cm 3 n / mPa s c / mol dm 3 p/ g cm 3 n / mPa s c / mol dm 3 p/ g cm 3 n / mPa s T = 278.15 K T = 293.15 K T = 308.15 K 0 1.045452 3.3327 0 1.035198 2.0895 0 1.024294 1.4125 0.0515 1.047771 3.3636 0.0510 1.037504 2.1082 0.0505 1.026603 1.4288 0.1031 1.049789 3.4111 0.1021 1.039571 2.1364 0.1011 1.028707 1.4524 0.1551 1.051892 3.4473 0.1536 1.041719 2.1605 0.1520 1.030855 1.4803 0.2072 1.054086 3.4884 0.2051 1.043886 2.1890 0.2030 1.033071 1.4990 0.2594 1.056172 3.5226 0.2569 1.045993 2.2078 0.2543 1.035207 1.5090 0.3120 1.058264 3.5661 0.3090 1.048112 2.2496 0.3059 1.037359 1.5338 T = 283.15 K T = 298.15 K T= 313.15 K 0 1.042102 2.8262 0 1.031640 1.8333 0 1.020403 1.2638 0.0513 1.044417 2.8567 0.0508 1.033946 1.8483 0.0503 1.022270 1.2864 0.1028 1.046451 2.8990 0.1018 1.036027 1.8698 0.1007 1.024834 1.3051 0.1546 1.048599 2.9378 0.1531 1.038175 1.8989 0.1514 1.026982 1.3228 0.2065 1.050751 2.9765 0.2045 1.040356 1.9235 0.2023 1.029218 1.3328 0.2586 1.052845 3.0101 0.2560 1.042247 1.9442 0.2533 1.031359 1.3544 0.3110 1.054945 3.0480 0.3080 1.044601 1.9742 0.3047 1.033520 1.3770 T = 288.15 K T = 303.15 K T= 318.15 K 0 1.038685 2.4198 0 1.028006 1.6008 0 1.016632 1.1485 0.0512 1.040990 2.4524 0.0507 1.030324 1.6167 0.0501 1.018814 1.1699 0.1025 1.043039 2.4890 0.1014 1.032407 1.6368 0.1003 1.020996 1.1762 0.1541 1.045187 2.5230 0.1525 1.034555 1.6596 0.1508 1.023144 1.1874 0.2058 1.047346 2.5586 0.2037 1.036752 1.6812 0.2015 1.025405 1.2071 0.2578 1.049447 2.6003 0.2552 1.038870 1.7035 0.2524 1.027545 1.2178 0.3100 1.051558 2.6285 0.3069 1.041011 1.7395 0.3036 1.029714 1.2364 Table 4. Experimental densities, p, and viscosities, n, as function of concentration, c, of NaCl solution in water-1,4-dioxane mixtures with mole fraction of 1,4- dioxane, xD = 0.20 at different temperatures. c / mol dm 3 p/ g cm 3 n / mPa s c / mol dm 3 p/ g cm 3 n / mPa s c / mol dm 3 p/ g cm 3 n / mPa s T = 278.15 K T = 293.15 K T = 308.15 K 0 1.05074 3.5444 0 1.03920 2.2420 0 1.02715 1.5131 0.0518 1.05306 3.6031 0.0512 1.04150 2.2680 0.0506 1.02946 1.5392 0.1036 1.05508 3.6543 0.1025 1.04357 2.3080 0.1013 1.03157 1.5587 0.1559 1.05718 3.7045 0.1542 1.04572 2.3514 0.1524 1.03371 1.5820 0.2082 1.05938 3.7568 0.2059 1.04789 2.3745 0.2036 1.03593 1.5963 0.2608 1.06146 3.8076 0.2580 1.04999 2.3927 0.2551 1.03807 1.6147 0.3136 1.06355 3.8630 0.3102 1.05211 2.4197 0.3067 1.04022 1.6372 T = 283.15 K T = 298.15 K T= 313.15 K 0 1.04695 3.0064 0 1.03523 1.9552 0 1.02300 1.3537 0.0516 1.04926 3.0570 0.0510 1.03754 1.9783 0.0504 1.02530 1.3799 0.1033 1.05130 3.0984 0.1021 1.03962 2.0019 0.1009 1.02743 1.3936 0.1553 1.05345 3.1401 0.1536 1.04177 2.0258 0.1518 1.02958 1.4099 0.2074 1.05560 3.1823 0.2052 1.04395 2.0552 0.2028 1.03181 1.4269 0.2599 1.05769 3.2230 0.2570 1.04606 2.0740 0.2541 1.03395 1.4398 0.3125 1.05979 3.2673 0.3090 1.04820 2.1205 0.3055 1.03612 1.4551 T = 288.15 K T = 303.15 K T= 318.15 K 0 1.04311 2.5757 0 1.03122 1.7027 0 1.01876 1.2145 0.0514 1.04541 2.6199 0.0508 1.03354 1.7283 0.0502 1.02104 1.2363 0.1029 1.04746 2.6538 0.1017 1.03562 1.7502 0.1005 1.02323 1.2475 0.1547 1.04961 2.6891 0.1530 1.03777 1.7746 0.1512 1.02537 1.2618 0.2067 1.05177 2.7284 0.2044 1.03997 1.8072 0.2020 1.02763 1.2811 0.2590 1.05387 2.7624 0.2561 1.04208 1.8248 0.2530 1.02977 1.2913 0.3113 1.05598 2.8034 0.3079 1.04423 1.8561 0.3043 1.03194 1.3102 In present study, the rearranged Jones-Dole equation (3) was applied. By help of the values of relative permittivity16 and viscosity (from present study) of the solvent, and limiting molar conductivities16 of the NaCl (Л°°), Na+ (Я+), and Cl- (Я-) at temperature T, values of A-coeffi-cients were calculated using equation (4). Applied parameters are given in Table 5 and Table S1 in Supporting information, whereas in Table 6 the values of estimated A-coefficients are listed. Figure 1. Plots of (nr- 1) - Ac1/2 against c for NaCl in water-1,4-dioxane mixtures at 293.15 K. Experimental values: O, xD = 0.05; □, xD = 0.10; A, xD = 0.15; V, xD = 0.20. Full lines are linear fits starting from the origin, and from their slopes B-coefficients were determined. In Figure 1 the plot of (nr - 1) - Ac1/2 (rearranged Jones-Dole eq. (3)) in dependence on concentration, c, at 293.15 K is presented. From the slopes viscosity B-coef-ficients were estimated by the assumption that the straight line must cross the origin. Obtained B-coeffi-cients are gathered in Table 7 for all investigated systems at all temperatures together with the literature data for NaCl in water.2 A comparison between obtained B-coefficients for NaCl in water-1,4-dioxane mixtures at 298.15 K with the literature data20 shows a reasonable agreement (Figure 2). Table 6. A-coefficients as calculated from Falkenhagen and Vernon eq. (4) for NaCl in water-1,4-dioxane mixtures at different temperatures.3 T / K XD 0.05 0.10 0.15 0.20 278.15 0.0061 0.0071 0.0081 0.0098 283.15 0.0062 0.0072 0.0083 0.0100 288.15 0.0063 0.0074 0.0084 0.0101 293.15 0.0064 0.0075 0.0085 0.0102 298.15 0.0065 0.0076 0.0086 0.0104 303.15 0.0067 0.0078 0.0088 0.0106 308.15 0.0067 0.0079 0.0090 0.0108 313.15 0.0068 0.0080 0.0091 0.0110 318.15 0.0069 0.0082 0.0092 0.0112 (a)Unit: A, dm3/2 mol-1/2 Viscosity A-coefficients, listed in Table 6, are positive at all temperatures. As stated, they depend on the relative permittivity and viscosity of the solvent, but also on the charge and the mobilities of ions and finally on temperature as well. Very small positive A-values suggest the presence of relative weak ion-ion interaction (Coulombic forces). From Table 6 thus it can be concluded that Coulombic forces are stronger in systems with higher content of 1,4-dio-xane - as it is expected due to lower permittivity of solvent mixture - and at higher temperatures. The B-coefficients are positive (Table 7) at all temperatures and bigger than A-coefficients (Table 6), showing the dominance of ions-solvent interaction over ionsions interaction. This finding can be confirmed by small association constant, KA, of NaCl in water-1,4-dioxane Table 5. The parameters of Falkenhagen and Vernon eq. (4) for NaCl in water-1,4-dioxane mixtures at 293.15 K. Input data in Eq. (4)a xD = 0.05 xD = 0.10 xD = 0.15 xD = 0.20 Я+Y S cm2 mol-1 33.07 25.50 21.99 19.35 Я°°/ S cm2 mol-1 48.19 36.42 31.05 26.97 Л°° / S cm2 mol-1 81.26 61.92 53.04 46.32 er 63.344 50.271 40.940 32.421 (a)Values are interpolated or extrapolated from literature data.16 Figure 2. Viscosity B-coefficients for NaCl in water-1,4-dioxane mixtures at 298.15 K: (□), this work; (O), Ref. 20. Table 7. The viscosity B-coefficients for NaCl in water-1,4-dioxa-ne mixtures at different temperatures.3 T / K 0.00b -D 0.05 0.10 0.15 0.20 278.15 0.034 0.124 0.151 0.206 0.267 283.15 0.053 0.129 0.152 0.235 0.260 288.15 0.063 0.137 0.155 0.264 0.263 293.15 0.071 0.146 0.158 0.215 0.248 298.15 0.080 0.129 0.174 0.221 0.231 303.15 0.083 0.160 0.181 0.241 0.266 308.15 0.088 0.145 0.181 0.265 0.249 313.15 0.093 0.141 0.190 0.271 0.234 318.15 0.098 0.142 0.196 0.225 0.237 (a)Unit: B, dm3 mol-1 ®Data from Ref. 2. mixtures with low content of 1,4-dioxane. As reported in16 KA 0) 0) what can be attributed to a structure-breaking nature of NaCl in these systems. Namely, with raising temperature hydrogen bonds are breaking and thus less structured water can be influenced by the ionic solute.20 Small change of the B-value with temperature for xD = 0.20 may be ascribed to the weakening of the ions-solvent interactions in comparison to solvent-solvent interactions. It is worth to mention, that water-1,4-dioxane binary mixtures show maximum in viscosity at xD « 0.2526,27,31 which can be ascribed to the strong interaction between 1,4-dioxane and water molecules. 4. Conclusions In present work, the B-coefficients of NaCl in wa-ter-1,4-dioxane binary mixtures in the temperature range from 278.15 to 318.15 K in four solvent mixtures with mole fraction of 1,4-dioxane, xD = 0.05, 0.10, 0.15 and 0.20, were determined by help of the rearranged Jones- Dole equation, 0, whereas - due to weak dependence of B on the temperature - this can be not assumed for xD = 0.20. It can be concluded that in solutions with lower content of 1,4-dioxane the structure-breaking nature of NaCl is prevailing and ions-solvent interactions are dominant. With increasing content of 1,4-dioxane the solvent-solvent interactions become more important, resulting finally also in a maximum in viscosity at 0.252 which can be attributed to the strong inte- raction between 1,4-dioxane and water molecules. It would be interesting to carry out this kind of research on the systems with higher content of 1,4-dioxane in the solvent. But according to the literature16 the association of NaCl increases dramatically with increasing amount of 1,4-dioxane and thus model, assuming negligible ion association applied in this study, can not be used. 5. Acknowledgments T.J. is grateful to Erasmus mobility grant enabling the research cooperation at University of Ljubljana and Dr. Bojan Šarac for all his help. The financial support from the Slovenian Research Agency through Grant No. P1-0201 and J1-0103-4148 is gratefully acknowledged. M. B.-R. would like to acknowledge Professor Dr. Jože Koller as a kind co-worker. 6. References 1. G. Hefter, P. M. May, P. Sipos, A. Stanley, J. Mol. Liq. 2003, 103-104, 261-273. http://dx.doi.org/10.1016/S0167-7322{02)00145-9 2. H. D. B. Jenkins, Y. Marcus, Chem. Rev. 1995, 95, 26952724. http://dx.doi.org/10.1021/cr00040a004 3. J. M. McDowall, N. Martinus, C. A. Vincent, J. Chem. Soc., Faraday Trans. 11976, 72 654-660. http://dx.doi.org/10.1039/f19767200654 4. J. Doménech, S. Rivera, Z. Phys. 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Owen, The Physical Chemistry of Electrolytic Solutions, 3rd Edition, Reinhold Publishing Corporation, New York, 1963, p. 236. 23. M. R. Cannon, R. E. Manning, J. D. Bell, Anal. Chem. 1960, 32, 355-358. http://dx.doi.org/10.1021/ac60159a015 24. IUPAC, Recommended Reference Materials for Realization of Physicochemical Properties. Section: Viscosity, Pure Appl. Chem. 1980, 52, 2395-2404. 25. O. Kratky, H. Leopold, H. N. Stabinger, Z. Angew. Phys. 1969, 27, 273-277. 26. L.-M. Omota, O. Iulian, O. Ciocirlan, I. Nita, Rev. Roum. Chim. 2008, 53, 977-988. 27. L.-M. Omota, O. Iulian, F. Omota, O. Ciocirlan, Rev. Roum. Chim. 2009, 54, 63-73. 28. B. Gurung, M. N. Roy, Solute-Solvent Interactions in Industrially Important Solvent Media, VDM Verlag Dr. Müller Aktiengesellschaft & Co. KG, Saarbrücken, 2010, pp. 13-39. 29. M. Kaminsky, Discuss. Faraday Soc. 1957, 24, 171-179. http://dx.doi.org/10.1039/df9572400171 30. Y. Marcus, Pure Appl. Chem. 2010, 82, 1889-1899. http://dx.doi.org/10.1351/PAC-CON-09-07-02 31. G. Ahn-Ercan, H. Krienke, G. Schmeer, J. Mol. Liq. 2006, 129, 75-79. http://dx.doi.org/10.1016/j.molliq.2006.08.004 Povzetek Izmerili smo viskoznosti raztopin NaCl v mešanicah vode in 1,4-dioksana (z molskim deležem 1,4-dioksana, xD = 0.05, 0.10, 0.15 in 0.20) v temperaturnem območju med 278.15 in 318.15 K. Dobljene vrednosti relativnih viskoznosti smo analizirali in razložili s pomočjo Jones-Dolove enačbe (nr - 1) - Ac1'2 = Bc. Koeficiente A smo pridobili z uporabo Falkenhagenove in Vernonove teorije, koeficiente B pa smo določili z linearno regresijo. Dobljene vrednosti B-koefi-cientov za NaCl v proučevanih topilih so pozitivne pri vseh temperaturah. Podatke smo primerjali s podatki iz literature za NaCl v vodi pri različnih temperaturah ter v mešanicah vode in 1,4-dioksana pri 298.15 K ter jih interpretirali s pomočjo možnih interakcij v preiskovanih raztopinah. Viscosity ^-Coefficient for Sodium Chloride in Aqueous Mixtures of 1,4-Dioxane at Different Temperatures# 1 * 1 2 Renato Tomaš, ' Toni Jovanović and Marija Bešter-Rogač 1Faculty of Chemistry and Technology, University of Split, Nikole Tesle 10, HR-21000 Split, Croatia. Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI- 1000 Ljubljana, Slovenia. * Corresponding author. E-mail: rtomas@ktf-split.hr # th Dedicated to Prof. Dr. Jože Koller on the occasion of his 70l" birthday Supporting Information: Table S1. Parameters used in Eq. (4) in aqueous mixtures of 1,4-dioxane at different temperatures. Input data in Eq. (4) = 0.05 *D = 0.10 *D = 0.15 *D = 0.20 T= 278.15 K A; / S cm2 mol-1 21.56 16.33 14.04 12.35 ЯГ / S cm2 mol-1 32.15 23.84 20.26 17.59 Л°° / S cm2 mol-1 53.71 40.17 34.30 29.94 er 68.388 54.584 44.575 35.395 T= 283.15 K A+ / S cm2 mol-1 25.14 19.15 16.47 14.49 Г / S cm2 mol-1 37.20 27.76 23.60 20.49 / S cm2 mol-1 62.34 46.91 40.07 34.98 er 66.644 53.181 43.382 34.370 T= 288.15 K a; / S cm2 mol-1 28.98 22.21 19.13 16.83 ЯГ / S cm2 mol-1 42.55 31.95 27.20 23.62 Л°° / S cm2 mol-1 71.53 54.16 46.33 40.45 er 64.955 51.659 42.088 33.322 T= 298.15 K a; / S cm2 mol-1 37.41 29.02 25.07 22.07 ЯГ / S cm2 mol-1 54.11 41.14 35.13 30.54 Л°° / S cm2 mol-1 91.52 70.16 60.20 52.61 er 61.759 48.921 39.774 31.425 T= 303.15 K A+ / S cm2 mol-1 41.99 32.75 28.33 24.97 A¥ / S cm2 mol-1 60.26 46.08 39.41 34.28 / S cm2 mol-1 102.25 78.83 67.74 59.25 er 60.181 47.626 38.720 30.596 T= 308.15 K A+ / S cm2 mol-1 46.77 36.69 31.80 28.05 A¥ / S cm2 mol-1 66.63 51.24 43.91 38.23 / S cm2 mol-1 113.40 87.93 75.71 66.28 er 58.673 46.359 37.658 29.730 T= 313.15 K A+ / S cm2 mol-1 51.55 40.63 35.27 31.13 A¥ / S cm2 mol-1 73.00 56.40 48.41 42.18 / S cm2 mol-1 124.55 97.03 83.68 73.31 er 57.165 45.092 36.596 28.864 T= 318.15 K A+ / S cm2 mol-1 56.33 44.57 38.74 34.21 A¥ / S cm2 mol-1 79.37 61.56 52.91 46.13 / S cm2 mol-1 135.70 106.13 91.65 80.34 er 55.657 43.825 35.534 27.998 1.04000 1.03500 1.03000 1.02500 Ii В ° 1.02000 1.01500 1.01000 1.00500 1.00000 ад 0.000 0.050 0.100 0.150 0.200 0.250 0.300 c / mol dm-3 2.600 2.400 2.200 2.000 (b) 1.800 - « < g 1.600 -Q--0- -0-0- -0-0- 1.000 0.800 0.600 Q о— —0— —о j)— —0— О —0— —0— о —е— —о О —0— —0— rs —о— п —о— —0— —0 —О —©— —У— и п —«— — i-Ö-w - 0.000 0.050 0.100 0.150 0.200 0.250 0.300 c / mol dm-3 О 278.15 K о 283.15 K о 288.15 K о 293.15 K о 298.15 K о 303.15 K о 308.15 K о 313.15 K о 318.15 K - r= 1.02247 + 0.0410 c (R = 0.9995) h= 2.3085 + 0.3040 c (R2 = 0.9879) - p= 1.02071 + 0.0410 c (R2 = 0.9995) h= 1.9618 + 0.2656 c (R2 = 0.9821) - p= 1.01881 + 0.0409 c (R = 1) h= 1.6880 + 0.2322 c (R = 0.9915) - p= 1.01672 + 0.0405 c (R2 = 0.9999) h= 1.4650 + 0.2173 c (R = 0.9907) - p= 1.01447 + 0.0404 c (R2 = 0.9999) h= 1.2865 + 0.1757 c (R2 = 0.9874) - p= 1.01204 + 0.0403 c (R2 = 0.9998) h= 1.1294 + 0.1811 c (R = 0.9845) - p= 1.00949 + 0.0402 c (R2 = 0.9998) h= 1.0156 + 0.1555 c (R2 = 0.9953) - p= 1.00680 + 0.0402 c (R2 = 0.9998) h= 0.9140 + 0.1374 c (R2 = 0.9943) - p= 1.00396 + 0.0401 c (R2 = 0.9996) h= 0.8244 + 0.1314 c (R2 = 0.9960) о ад 1.05000 - 1.04000 - 1.03000 1.02000 1.01000 0.000 0.050 0.100 0.150 0.200 0.250 0.300 c / mol dm-3 3.000 I- 2.500 ев Рч m 2.000 1.500 1.000 - о -©— —0— —О Г- —©— - и )-Ö— —0— и —е— —0— —© )—0— —G— —©— о —©— о —©— —©— —0 —О ?- — —У— и о —0— —0 э-0— —У— - KJ л Г\ —<=>— —о л-1)-КГ w ~ ~ 0.000 0.050 0.100 0.150 0.200 0.250 0.300 c / mol dm-3 О 278.15 K О 283.15 K О 288.15 K О 293.15 K О 298.15 K О 303.15 K О 308.15 K О 313.15 K О 318.15 K - p = 1.03698 + 0.0401 c (R2 = 0.9991 h = 2.9331 + 0.4818 c (R2 = 0.9935) - p = 1.03425 + 0.0399 c (R2 = 0.9992 h = 2.4846 + 0.4127 c (R2 = 0.9957) - p= 1.03140 + 0.0399 c (R2 = 0.9994 h = 2.1250 + 0.3617 c (R2 = 0.9925) - p= 1.02846 + 0.0397 c (R2 = 0.9993 h= 1.8358 + 0.3238 c (R2 = 0.9910) - p= 1.02542 + 0.0397 c (R2 = 0.9993 h = 1.6007 + 0.3200 c (R2 = 0.9868) - p= 1.02229 + 0.0398 c (R2 = 0.9994 h= 1.4042 + 0.2797 c (R2 = 0.9877) - p= 1.01905 + 0.0398 c (R2 = 0.9994 h= 1.2506 + 0.2326 c (R2 = 0.9892) - p= 1.01572 + 0.0399 c (R2 = 0.9994 h= 1.1188 + 0.2143 c (R2 = 0.9888) - p= 1.01229 + 0.0400 c (R2 = 0.9994 h= 1.0058 + 0.2045 c (R2 = 0.9857) 1.01000 0.000 0.050 0.100 0.150 0.200 0.250 0.300 c / mol dm ■3 3.500 3.000 Рч s 2.000 1.500 1.000 O 278. O 283. O 288. O 293. O 298. O 303. O 308. O 313. O 318. - P = h = P = h = — r= h = — r= h = r= h = — r= h = -r = h = — r= h = — r= h = .15 K .15 K .15 K .15 K .15 K .15 K .15 K .15 K .15 K 1.04556 + 0.0409 c (ff = 0.9998 3.3304 + 0.7525 c (ff = 0.9986) 1.04221 + 0.0411 c (ff = 0.9998 2.8242 + 0.7233 c (ff = 0.9990) 1.03879 + 0.0414 c (ff2 = 0.9998 2.4186 + 0.6854 c (ff = 0.9989) 1.03530 + 0.0416 c (ff2 = 0.9998 2.0848 + 0.5079 c (ff = 0.9922) 1.03176 + 0.0416 c (ff2 = 0.9995 1.8275 + 0.4651 c (ff2 = 0.9947) 1.02811 + 0.0422 c (ff2 = 0.9998 1.5949 + 0.4430 c (ff = 0.9888) 1.02438 + 0.0426 c (ff2 = 0.9999 1.4127 + 0.3999 c (ff2 = 0.9897) 1.02033 + 0.0435 c (ff2 = 0.9993 1.2666 + 0.3540 c (ff = 0.9928) 1.01665 + 0.0431 c (ff2 = 0.9999 1.1502 + 0.2756 c (ff2 = 0.9871) 0.000 0.050 0.100 0.150 0.200 0.250 0.300 c / mol dm 3 ад 1.07000 1.06000 - 1.05000 1.04000 1.03000 1.02000 1.01000 0.000 0.050 0.100 0.150 0.200 0.250 0.300 c / mol dm ■3 4.000 3.500 3.000 ев Рч m 2.500 2.000 1.500 1.000 0.000 0.050 0.100 0.150 0.200 0.250 0.300 c / mol dm 3 О 278.15 K о 283.15 K о 288.15 K о 293.15 K о 298.15 K о 303.15 K о 308.15 K о 313.15 K о 318.15 K - р= 1.0509 + 0.0407 c (R = 0.9998) h= 3.5481 + 1.0026 c (R = 0.9996) r= 1.0471 + 0.0409 c (R2 = 0.9998) h= 3.0112 + 0.8219 C (R = 0.9991) r= 1.0432 + 0.0412 c (R2 = 0.9998) h= 2.5790 + 0.7176 c (R = 0.9990) - r= 1.0393 + 0.0415 c (R2 = 0.9998) h= 2.2460 + 0.5863 c (R2 = 0.9826) r= 1.0353 + 0.0418 c (R2 = 0.9998) h= 1.9510 + 0.5137 c (R = 0.9881) - r= 1.0313 + 0.0421 c (R2 = 0.9998) h= 1.7019 + 0.4943 c (R = 0.9972) - r= 1.0272 + 0.0425 c (R2 = 0.9999) h= 1.5174 + 0.3918 c (R2 = 0.9950) r= 1.0231 + 0.0428 c (R2 = 0.9999) h= 1.3596 + 0.3206 c (R = 0.9907) - r= 1.0188 + 0.0432 c (R2 = 0.9999) h= 1.2173 + 0.3033 c (R = 0.9943) 1.05000 1.04000 1.03000 E " 1.02000 то 1.01000 1.00000 ..О"' € /ia T = 293.15 K T = 303.15 K (a) 0.99000 -L _L -L _L _L 0.0000 0.0500 0.1000 0.1500 XD 0.2000 0.2500 0.3000 2.600 2.400 2.200 2.000 w 1.800 a £ 1.600 S- 1.400 1.200 1.00 0.800 0.600 0.0000 0.0500 0.1000 0.1500 0.2000 0.2500 0.3000 Figure S5. Measured values of density (a), and viscosity (b) of water-1,4-dioxane mixtures at two selected temperatures of 293.15 K and 303.15 K together with the data reported in literature. o, this work; A, Ref. 16.; □, Ref. 27.; ■, Ref. 26. in the manuscript.