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Original article
10 (
1_suppl
); S71-S75
doi:
10.1016/j.arabjc.2012.07.012

Density, viscosity, surface tension, and molar volume of propylene glycol + water mixtures from 293 to 323 K and correlations by the Jouyban–Acree model

Department of Pharmaceutics, Faculty of Pharmacy, Kuwait University, Kuwait
Tuberculosis and Lung Disease Research Center, Tabriz University of Medical Sciences, Tabriz 51664, Iran
Drug Applied Research Center and Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz 51664, Iran

⁎Corresponding author. Tel.: +98 411 3379323; fax: +98 411 3363231. ajouyban@hotmail.com (Abolghasem Jouyban)

Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.

Peer review under responsibility of King Saud University.

Abstract

Density, viscosity, surface tension and molar volume of propylene glycol + water mixtures at 293, 298, 303, 308, 313, 318, and 323 K are reported, compared with the available literature data and the Jouyban–Acree model was used for mathematical correlation of the data. The mean relative deviation (MRD) was used as an error criterion and the MRD values for data correlation of density, viscosity, surface tension and molar volume at different investigated temperatures are 0.1 ± 0.1%, 7.6 ± 6.4%, 3.4 ± 3.7%, and 0.4 ± 0.4%, respectively. The corresponding MRDs for the predicted properties after training the model using the experimental data at 298 K are 0.1 ± 0.2%, 12.8 ± 9.3%, 4.7 ± 4.1% and 0.6 ± 0.5%, respectively for density, viscosity, surface tension, and molar volume data.

Keywords

Density
Viscosity
Surface tension
Molar volume
Propylene glycol + water
Binary mixture
Jouyban–Acree model
1

1 Introduction

Density, viscosity, surface tension and molar volume of liquids are important physicochemical properties (PCPs) which affect mass and heat transfer processes in solutions. So, availability of the related data should be helpful in designing and engineering of such processes. As an example, Tubtimdee and Shotipurk (2011) reported that in the extraction of phenolic compounds from a plant source, employing propylene glycol + water or ethanol + water mixtures require lower temperatures when compared with the mono-solvent extraction systems (Tubtimdee and Shotipurk, 2011). It is obvious that using lower temperatures for extraction of thermal liable compounds like phenolics is more valuable.

It has been observed that PCPs of solvent mixtures show deviation from ideal mixing and finding a suitable blend of solvents for a desired amount of PCP requires some experimental determinations, or accurate models. Despite the experimental determination of PCPs, a number of mathematical models have been presented for calculating PCP data. Among the similar models for correlation of PCPs of liquid mixture, the Jouyban–Acree model is perhaps one of the most accurate models (Jouyban et al., 2004a,b,c; 2005a,b,2006; Hasan et al., 2006; Delgado et al., 2012). The model for correlation of PCPs of the binary solvent mixtures at various temperatures is:

(1)
ln PCP m , T = x 1 · ln PCP 1 , T + x 2 · ln PCP 2 , T + J 0 x 1 · x 2 T + J 1 x 1 · x 2 · ( x 1 - x 2 ) T + J 2 x 1 · x 2 · ( x 1 - x 2 ) 2 T where PCPm,T, PCP1,T, and PCP2,T are the physicochemical properties under study of the mixture, solvents 1 and 2, respectively; x1 and x2 denote mole fractions of the solvents 1 and 2, respectively; T is the absolute temperature; and Ji terms are the coefficients of the model which are computed by regressing ( ln PCP m , T - x 1 · ln PCP 1 , T - x 2 · ln PCP 2 , T ) against x 1 · x 2 T , x 1 · x 2 · ( x 1 - x 2 ) T and x 1 · x 2 · ( x 1 - x 2 ) 2 T using a no-intercept regression analysis.

The aims of this work are to report density, viscosity, surface tension and molar volume of propylene glycol + water mixtures at different temperatures and to give a predictive model for these properties.

2

2 Experimental

2.1

2.1 Materials

Propylene glycol was purchased from Merck, Germany. The water used in this study was of Ultra pure reagent grade type 1 water, prepared using a Millipore water purifier system (Milli-Q Synthesis, France) with the conductivity of 5.49 × 10−6 S m−1 and TOC < 10 ppb.

2.2

2.2 Apparatus and procedures

Suitable proportions of the solvents were mixed with each other volumetrically with an uncertainty of 0.1 mL to produce different blends of propylene glycol and water by intervals of 0.10 in volume fraction. The prepared solvent mixtures were placed on a shaking water bath (Memmert, Germany) with set temperature accuracy of 0.1 °C at 293, 298, 303, 308, 313, 318, and 323 K. After at least 2 h and on assurance of equilibrium, the samples were analyzed. Mettler Toledo Densito Portable 30PX Density Meter (USA) was used for density measurements of the equilibrated solvent mixtures. The viscosity of the solvent mixtures was measured using an Ostwald U-tube glass viscometer (Union Scientific Appliances, India) suspended in a constant temperature water bath. Surface tension of the prepared blends of solvents was determined by drop number method. The accuracy of reported data was 0.0001 (g cm−3), 0.0001 (mPag s), and 0.01 (mNg m−1) for density, viscosity, and surface tension, respectively. The lowest and highest standard deviations of the measurements for density were 0.0001 and 0.0008 with an overall relative standard deviation of 0.08%. These values were 0.0032, 0.0719, and 1.32% for viscosity, and 0.1534, 0.9549, and 1.12% for surface tension measurements, respectively. All measurements were done at least in triplicates.

2.3

2.3 Computational methods

The Jouyban–Acree model was used as a mathematical model for correlation of the studied PCPs in solvent mixtures. For this purpose, for each property under investigation, it has been trained with experimental data using a no-intercept regression analysis. The molar volumes (V) for binary mixtures are calculated by:

(2)
V m , T = x 1 M 1 + x 2 M 2 ρ m , T where M1 and M2 are the molar masses of solvents 1 and 2, respectively. The mean relative deviation (MRD) was used as error criterion as:
(3)
MRD = 100 N | PCP Exp - PCP Cal | PCP Exp
where N is the number of data points in each set, PCPExp and PCPCal are the experimental and calculated PCPs under investigation.

3

3 Results and discussion

Experimental and calculated values of density, viscosity, surface tension and molar volume data are listed in Table 1. The behavior of density in mixtures of propylene glycol + water shows a peak at a mole fraction of ∼0.4 of propylene glycol. The viscosity of the binary mixtures was increased non-linearly with the mole fraction of propylene glycol. The change trend of surface tension in propylene glycol + water mixtures is decreased with the increased mole fraction of propylene glycol. Increasing pattern is observed with the molar volume data of the mixtures with respect to the mole fraction of propylene glycol.

Table 1 Mole fraction of propylene glycol (x1), experimental and calculated (by Eqs. ()()()()(4)–(7)) data of density (ρ), viscosity (η), surface tension (σ), and molar volume (V) of propylene glycol + water binary mixtures at different temperatures.
x1 ρ × 10−3 (kg m−3) η × 10−3 (Pa s) σ × 10−3 (N m−1) V (cm3 mol−1)
Expt Cal Expt Cal Expt Cal Expt Cal
T = 293 (K)
0.000 0.9978 0.9978 1.003 1.003 72.88 72.88 18.04 18.04
0.027 1.0051 1.0062 1.434 1.277 63.11 68.17 19.44 19.43
0.058 1.0136 1.0147 1.975 1.667 57.61 63.50 21.07 21.10
0.095 1.0227 1.0229 2.780 2.242 51.61 58.93 23.01 23.12
0.141 1.0312 1.0304 3.826 3.115 47.60 54.57 25.38 25.61
0.197 1.0365 1.0368 5.325 4.484 43.72 50.56 28.41 28.74
0.269 1.0408 1.0410 9.235 6.694 42.26 47.15 32.31 32.74
0.364 1.0427 1.0424 12.021 10.344 41.40 44.66 37.55 38.03
0.495 1.0425 1.0409 18.332 16.462 40.50 43.57 44.87 45.36
0.688 1.0401 1.0390 29.494 27.263 39.55 43.80 55.75 56.36
1.000 1.0353 1.0353 57.571 57.571 38.57 38.57 73.50 73.50
T = 298 (K)
0.000 0.9958 0.9958 0.976 0.976 69.06 69.06 18.08 18.08
0.027 1.0031 1.0040 1.170 1.228 59.80 64.87 19.48 19.46
0.058 1.0113 1.0123 1.569 1.582 55.66 60.71 21.12 21.11
0.095 1.0202 1.0204 2.346 2.095 51.22 56.65 23.06 23.12
0.141 1.0282 1.0278 3.331 2.857 49.04 52.79 25.45 25.60
0.197 1.0333 1.0340 4.529 4.021 46.93 49.29 28.49 28.70
0.269 1.0376 1.0381 6.757 5.842 45.68 46.39 32.40 32.69
0.364 1.0393 1.0395 9.864 8.726 44.72 44.45 37.66 37.96
0.495 1.0389 1.0379 14.508 13.277 43.72 44.01 45.01 45.29
0.688 1.0367 1.0361 22.908 20.648 42.68 45.22 55.92 56.33
1.000 1.0323 1.0323 39.436 39.436 41.31 41.31 73.71 73.71
T = 303 (K)
0.000 0.9938 0.9938 0.937 0.937 65.59 65.59 18.11 18.11
0.026 1.0007 1.0018 1.026 1.165 60.27 61.83 19.52 19.48
0.058 1.0086 1.0099 1.396 1.481 56.74 58.10 21.17 21.12
0.095 1.0166 1.0177 1.976 1.931 52.26 54.48 23.13 23.12
0.140 1.0242 1.0248 2.727 2.585 49.66 51.05 25.53 25.58
0.197 1.0294 1.0308 3.513 3.560 48.34 47.97 28.58 28.66
0.268 1.0329 1.0348 5.086 5.037 47.37 45.49 32.52 32.63
0.363 1.0347 1.0359 7.424 7.276 47.83 44.00 37.80 37.90
0.495 1.0342 1.0341 10.524 10.600 46.72 44.11 45.18 45.24
0.688 1.0335 1.0319 16.043 15.505 44.66 46.12 56.07 56.36
1.000 1.0276 1.0276 26.852 26.852 43.46 43.46 74.05 74.05
T = 308 (K)
0.000 0.9918 0.9918 0.862 0.862 64.46 64.46 18.15 18.15
0.026 0.9983 0.9996 0.956 1.063 59.89 60.87 19.57 19.51
0.057 1.0063 1.0074 1.154 1.339 56.46 57.31 21.21 21.14
0.095 1.0136 1.0150 1.560 1.728 52.49 53.83 23.19 23.12
0.140 1.0207 1.0220 2.201 2.287 50.28 50.55 25.60 25.56
0.196 1.0253 1.0277 3.160 3.108 48.16 47.61 28.67 28.63
0.268 1.0288 1.0315 4.091 4.328 47.22 45.25 32.63 32.58
0.363 1.0317 1.0324 5.698 6.132 46.65 43.88 37.88 37.84
0.494 1.0302 1.0304 7.847 8.718 45.54 44.11 45.32 45.19
0.687 1.0285 1.0279 12.054 12.336 44.83 46.28 56.31 56.38
1.000 1.0231 1.0231 20.267 20.267 43.96 43.96 74.37 74.37
T = 313 (K)
0.000 0.9884 0.9884 0.761 0.761 63.93 63.93 18.21 18.21
0.026 0.9951 0.9961 0.848 0.932 58.41 60.40 19.63 19.56
0.058 1.0029 1.0038 1.069 1.166 54.09 56.90 21.28 21.19
0.095 1.0103 1.0112 1.421 1.492 51.70 53.48 23.26 23.16
0.140 1.0167 1.0181 1.863 1.956 50.73 50.23 25.70 25.59
0.196 1.0233 1.0237 2.563 2.627 49.81 47.32 28.73 28.65
0.268 1.0244 1.0275 3.526 3.608 47.18 44.97 32.77 32.59
0.363 1.0294 1.0285 4.640 5.028 45.99 43.58 37.96 37.83
0.494 1.0257 1.0266 6.449 7.001 45.15 43.73 45.53 45.18
0.687 1.0233 1.0242 9.269 9.632 44.07 45.73 56.60 56.42
1.000 1.0197 1.0197 15.136 15.136 43.30 43.30 74.62 74.62
T = 318 (K)
0.000 0.9840 0.9840 0.721 0.721 62.67 62.67 18.29 18.29
0.026 0.9912 0.9914 0.784 0.878 56.54 59.29 19.70 19.64
0.057 0.9989 0.9988 0.964 1.092 53.44 55.93 21.35 21.25
0.094 1.0065 1.0060 1.230 1.387 50.30 52.64 23.33 23.21
0.139 1.0125 1.0126 1.705 1.805 49.37 49.52 25.78 25.63
0.196 1.0151 1.0179 2.116 2.404 48.71 46.71 28.93 28.68
0.267 1.0200 1.0214 2.869 3.271 47.81 44.45 32.87 32.62
0.362 1.0216 1.0221 4.185 4.508 45.41 43.12 38.20 37.87
0.493 1.0177 1.0198 5.161 6.197 44.59 43.29 45.83 45.26
0.686 1.0142 1.0168 7.955 8.387 44.12 45.32 57.06 56.63
1.000 1.0114 1.0114 12.844 12.844 43.07 43.07 75.23 75.23
T = 323 (K)
0.000 0.9715 0.9715 0.675 0.675 62.02 62.02 18.53 18.53
0.027 0.9826 0.9790 0.701 0.820 58.20 58.82 19.89 19.89
0.058 0.9917 0.9865 0.907 1.015 55.32 55.66 21.53 21.51
0.095 1.0009 0.9938 1.055 1.284 54.03 52.58 23.50 23.49
0.140 1.0065 1.0006 1.569 1.659 53.47 49.68 25.99 25.93
0.197 1.0107 1.0063 1.961 2.193 53.27 47.12 29.13 29.00
0.269 1.0160 1.0102 2.697 2.953 51.52 45.15 33.09 32.95
0.364 1.0159 1.0117 3.759 4.020 50.00 44.18 38.53 38.22
0.495 1.0119 1.0106 4.802 5.437 48.04 44.86 46.21 45.63
0.688 1.0082 1.0095 7.319 7.207 47.20 47.67 57.50 57.00
1.000 1.0069 1.0069 10.691 10.691 46.47 46.47 75.57 75.57

Available experimental data of density, viscosity, and surface tension of water and propylene glycol at different temperatures from the literature (MacBeth and Thompson, 1951; Nakanishi et al., 1967; Hoke and Patton, 1992; Geyer et al., 2000; George and Sastry, 2003; Sun and Teja, 2004; Jiménez and Martínez, 2005) were compared with listed data in Table 1. MacBeth and Thompson (1951) reported the density of propylene glycol + water mixtures at 308 K. Nakanishi et al. (1967) measured densities of aqueous mixtures of glycols at 298.15 K and calculated their excess molar volumes. Surface tensions at 298, 303, 308, 313, 318 and 323 K have been reported by Hoke and Patton (1992). Geyer et al. (2000) published densities of binary mixtures of four diols including propylene glycol at 278.15, 288.15, 298.15, 308.15 and 318.15 K. George and Sastry (2003) measured the density, viscosity, speed of sound and dielectric constants of propylene glycol + water mixtures and some other alkanediol + water mixtures at 298, 308, 318, 328 and 338 K. Density, viscosity and thermal conductivity of aqueous mixtures of propylene glycol, dipropylene glycol and tripropylene glycol at different temperatures (290–460 K) have been reported by Sun and Teja (2004). There are good agreements between available data from the literature and newly generated data in this work. Density of propylene glycol + water mixtures at 293.15, 298.15, 303.15, 318.15, and 323.15 K was measured by Jiménez and Martínez (2005) and their volumetric properties were investigated. Our measured values differ from the published literature values by no more than 0.002. The measured data cover a wider temperature range and also could be used to evaluate the reproducibility of the data measured in different laboratories.

The resulted equations for density, viscosity, surface tension and molar volume calculations using the Jouyban–Acree model are:

(4)
ln ρ m , T = x 1 · ln ρ 1 , T + x 2 · ln ρ 2 , T + 27.820 x 1 · x 2 T - 30.537 x 1 · x 2 · ( x 1 - x 2 ) T + 30.476 x 1 · x 2 · ( x 1 - x 2 ) 2 T
(5)
ln η m , T = x 1 · ln η 1 , T + x 2 · ln η 2 , T + 926.206 x 1 · x 2 T - 606.410 x 1 · x 2 · ( x 1 - x 2 ) T
(6)
ln σ m , T = x 1 · ln σ 1 , T + x 2 · ln σ 2 , T - 183.307 x 1 · x 2 T + 197.808 x 1 · x 2 · ( x 1 - x 2 ) T - 456.916 x 1 · x 2 · ( x 1 - x 2 ) 2 T
(7)
ln V m , T = x 1 ln V 1 , T + x 2 ln V 2 , T + 264.365 x 1 x 2 T - 101.545 x 1 x 2 ( x 1 - x 2 ) T + 62.243 x 1 · x 2 · ( x 1 - x 2 ) 2 T
where ρ, η, σ and V are indicators of density, viscosity, surface tension and molar volume; 1, 2, and m subscripts stand for propylene glycol, water and their mixtures, respectively. The coefficient of determination (R2) values for Eqs. (4)–(7) are 0.992, 0.965, 0.916, and 0.999, respectively.

All of these PCPs were correlated perfectly using the Jouyban–Acree model with overall MRD values of 0.1 ± 0.1%, 7.6 ± 6.4%, 3.4 ± 3.7%, and 0.4 ± 0.4% for density, viscosity, surface tension, and molar volume data, respectively. The model could be trained using measured data at 298 K and the PCP data at other temperatures and solvent compositions could be predicted by employing PCP data of mono-solvents at each temperature of interest, i.e. PCP1,T and PCP2,T. The resulted MRD values for predicted density, viscosity, surface tension, and molar volume data (N = 66) are 0.1 ± 0.2%, 12.8 ± 9.3%, 4.7 ± 4.1% and 0.6 ± 0.5%, respectively. The Jouyban–Acree model also produced the most accurate results among other similar models for representing the solubility of drugs in mixed solvents (Jouyban-Gharamaleki et al., 1999), solubility of solutes in binary mixtures of supercritical fluids (Jouyban et al., 2005b), acid dissociation constants of analytes in binary mixtures (Jouyban et al., 2005e), electrophoretic mobility of charged species in capillary electrophoresis (Jouyban-Gharamaleki et al., 2000) and retention factors of analytes in high performance liquid chromatography (Jouyban et al., 2005d). All these solutions PCP have been represented using the universal form of the Jouyban–Acree model, i.e., Eq. (1), whereas different algorithms were used in the literature for representing these PCPs. Training of these models (including the Jouyban–Acree model) is their main drawback which restricts their practical application. To overcome this restriction, two solutions could be employed; (a) training the model by a minimum number of experimental data and predicting the unmeasured data points (Jouyban et al., 2004a, 2005a,c) and (b) employing the globally trained version of the model (Jouyban et al., 2011) to predict the PCPs.

4

4 Conclusion

As a conclusion, the PCP data of propylene glycol + water mixtures are reported at 293 to 323 K and the model constants of the data are computed. Using these constants, it is possible to predict the PCP data in all solvent compositions of propylene glycol + water at various temperatures using the interpolation technique. The trained equations, i.e. Eqs. (4)–(7), are valid for propylene glycol + water mixtures. It is possible to include some descriptors to represent the effects of the solvent properties to provide global versions of the model. Such models have been reported for viscosity (Jouyban et al., 2011) and density (Jouyban et al., 2012) of mixed solvents at various temperatures.

Acknowledgment

A. Jouyban would like to thank Dr Aly Nada, Head of Pharmaceutics Department, Faculty of Pharmacy, Kuwait University, for his invitation to visit the faculty and arranging this collaboration.

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