1 Introduction

Knowledge of the temperature dependence of excess volumetric and transport properties of liquid mixtures provides valuable information on the nature of inter molecular interactions existing among the component molecules [1–3]. In continuation of our previous research, recently we reported ultrasonic and volumetric studies of the binary mixtures of N,N-dimethyl formamide with acrylic esters [4]. Alkanol molecules are polar and self-associated through hydrogen bonding of their hydroxyl groups [5]. Propanoic acid molecules are also polar. N,N-dimethyl formamide has a large dipole moment μ = 3.82 [6] and, in view of this, dipole–dipole interactions are expected to play an important role in molecular interactions present in the liquid mixtures. Alkanols are interesting simple examples of biological and industrial important amphiphilic materials [7]. Propanoic acid is a naturally occurring carboxylic acid and is used as an intermediate in the production of other chemicals, especially polymers, plastics, and cosmetics. Amides, relevant liquid systems for the study of molecular interactions, are among the most common solvents used in chemical reactions and in many industrial processes.

Some excess properties of binary liquid mixtures of propanoic acid with aniline, o-toluidine, o-anisidine, and o-chloroaniline were reported by Garcia et al. [8]. Solimo et al. [9] reported the thermodynamic properties of binary liquid acid–base mixtures. Viscosities and densities of binary mixtures of toluene with acetic acid and propanoic acid at several temperatures were reported by Rattan et al. [10]. As there are no temperature-dependent studies of similar liquid mixtures, particularly for the volumetric and transport properties of the present liquid mixtures, the present study of the liquid mixtures of propanoic acid with equimolar mixtures of N,N-dimethyl formamide and methanol/ethanol/1-propanol at three temperatures T/K = 303.15, 313.15, and 323.15 over the entire mole fraction range, x 1, of propanoic acid, is expected to reveal new and interesting results on molecular interactions.

In the present investigation, we report densities, ρ, and viscosities, η, of the liquid mixtures at three different temperatures. The excess and deviation properties such as excess molar volume, \( V_{\text{m}}^{\text{E}} \), deviation in viscosity, Δη, and excess

Gibbs energy of activation of viscous flow, ΔG *E, have been calculated using the experimental values of ρ and η. The variation of \( V_{\text{m}}^{\text{E}} \), Δη and ΔG *E with composition and temperature are discussed in terms of molecular interactions occurring among the molecules of these mixtures.

2 Experimental Details

Propanoic acid (PA), N,N-dimethyl formamide (DMF), methanol (MOH), ethanol (EOH) and 1-propanol (POH) used in the present study were AR grade products from LOBA Chemicals, India and were purified by standard methods described in the literature [11, 12]. The mass fraction purity of the liquids obtained are >0.995. Before use, the chemicals were stored over 0.4 nm molecular sieves for approximately 72 h to remove water and then degassed.

The mixtures were prepared by mass in air-tight bottles. The mass measurements were performed with a METTLER TOLEDO (Switzerland) ABB5-S/FACT digital balance with an accuracy ±0.01 mg. The uncertainty in the mole fractions is 1 × 10–4. Densities and viscosities of pure liquids and liquid mixtures have been determined using a 5 cm3 two-stem double-walled Parker and Parker type pyknometer [13] and an Ostwald viscometer that was calibrated as described by Naidu and Ravindra Prasad [14], using triply distilled water. The detailed experimental procedures adopted for the measurement of ρ and η are the same as in our earlier studies reported in the literature [4, 15, 16]. The reproducibility in the measured densities and viscosities are 3 in 105 parts and ±0.2 %, respectively. The densities and viscosities of the pure liquids used in this investigation, at T/K = 303.15, 313.15, and 323.15, are compiled in Table 1 together with the available literature data [10, 12, 17–26]. These results are found to be in good agreement with the reported literature data.

Table 1 Comparison of experimental values of the density, ρ, and viscosity, η, of pure liquids with their corresponding literature values
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3 Results and Discussion

The experimentally measured values of ρ and η were used to calculate the excess and deviation properties \( V_{\text{m}}^{\text{E}} \), Δη, and ΔG *E using the following equations:

$$ V_{\text{m}}^{\text{E}} = V_{\text{m}} - \left( {x_{1} V_{1}^{ * } + x_{2} V_{2}^{ * } } \right) $$
(1)
$$ \Updelta \eta = \eta - \left( {x_{1} \eta_{1}^{ * } + x_{2} \eta_{2}^{ * } } \right) $$
(2)
$$ \Updelta G^{{*{\text{E}}}} = RT\left[ {ln\left( {\eta V_{\text{m}} } \right) - x_{ 1} ln\left( {\eta_{1}^{*} V_{1}^{*} } \right) - x_{2} ln\left( {\eta_{2}^{*} V_{2}^{*} } \right)} \right] $$
(3)

where V m and η are the molar volume and viscosity of the mixture. \( V_{1}^{ * } \) and \( \eta_{1}^{ * } \) are the molar volumes and viscosities of pure component 1 (propanoic acid) and \( V_{2}^{ * } \) and \( \eta_{2}^{ * } \) are the effective molar volume and viscosity of an equimolar mixture of component 2 (N,N-dimethyl formamide +, methanol, ethanol, 1-propanol), respectively, and x i represents the mole fraction of component ‘i’ in the mixture.

The experimental values of ρ and η and calculated values of \( V_{\text{m}}^{\text{E}} \), Δη, and ΔG *E are reported in Tables 2, 3 and 4 for the studied systems at different temperatures over the entire mole fraction, x 1, of PA. It was observed that the density varies monotonically with the concentration of propanoic acid at all temperatures, but the viscosity changes non-linearly showing a maximum at about x 1 ≈ 0.6 in the PA-rich region at all investigated temperatures in all of the systems. The observed maxima (peaks) were found to increase with increasing chain length of alcohols. Such deviations may be attributed to specific interactions arising from the formation of complexes among the mixing molecules.

Table 2 Experimental values of the density, ρ, viscosity, η, and calculated properties excess molar volumes, \( V_{\text{m}}^{\text{E}} \), deviation in viscosities, Δη, and excess Gibbs energy of activation of viscous flow, ΔG *E, as functions of the mole fraction of PA, x 1, for the (DMF + MOH) + PA system at T/K = 303.15, 313.15 and 323.15 (the mole fractions of DMF and MOH are equal)
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Table 3 Experimental values of the density, ρ, viscosity, η, and calculated properties excess molar volumes, \( V_{\text{m}}^{\text{E}} \), deviation in viscosities, Δη, and excess Gibbs energy of activation of viscous flow, ΔG *E, as functions of the mole fraction of PA, x 1, for the (DMF + EOH) + PA system at T/K = 303.15, 313.15 and 323.15 (the mole fractions of DMF and EOH are equal)
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Table 4 Experimental values of the density, ρ, viscosity, η, and calculated properties excess molar volumes, \( V_{\text{m}}^{\text{E}} \), deviation in viscosities, Δη, and excess Gibbs energy of activation of viscous flow, ΔG *E, as functions of the mole fraction of PA, x 1, for the (DMF + POH) + PA system at T/K = 303.15, 313.15 and 323.15 (the mole fractions of DMF and POH are equal)
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The deviation/excess properties have been fitted to a Redlich–Kister type polynomial [27] equation:

$$ \Updelta Y = x_{1} x_{2} \sum\limits_{i = 0}^{4} {A_{i} \left( {x_{2} - x_{1} } \right)^{i} } $$
$$ Y^{\text{E}} = x_{1} x_{2} \sum\limits_{i = 0}^{4} {A_{i} \left( {x_{2} - x_{1} } \right)^{i} } $$
(4)

where ΔY = Δη and Y E = \( V_{\text{m}}^{\text{E}} \) or ΔG *E. The A i are adjustable parameters of this function and are determined using the least-squares method. The corresponding standard deviations \( \sigma \left( {Y^{\text{E}} } \right) \) have been computed using the relation:

$$ \sigma \left( {Y^{\text{E}} } \right) = \left[ {\frac{{\Upsigma \left( {Y_{\exp }^{\text{E}} - Y_{\text{cal}}^{\text{E}} } \right)^{2} }}{{\left( {m - n} \right)}}} \right]^{1/2} $$
(5)

where ‘m’ is the total number of experimental points and ‘n’ is the number of coefficients in Eq. 4. The coefficients A i , and the standard deviations σ, of all of the liquid mixtures are presented in Table 5.

Table 5 Coefficients A i of the Redlich–Kister type polynomial, Eq. 4, and the corresponding standard deviations for all of the studied systems
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The variations of \( V_{\text{m}}^{\text{E}} \) for all of the systems, at different temperatures, are shown in Figs. 1, 2 and 3. Figure 4 shows the variation of Δη with mole fraction of PA at all temperatures for the (DMF + MOH) + PA system. The corresponding plot of Δη versus concentration at T/K = 313.15 is shown in Fig. 5. The variations of ΔG *E with mole fraction of PA for all of the systems at T/K = 323.15 are represented in Fig. 6. The observed negative \( V_{\text{m}}^{\text{E}} \) and positive Δη and ΔG *E values reveal that strong interactions exist among unlike molecules of the mixtures. The factors that are mainly responsible for the expansion of molar volume, i.e. positive values of \( V_{\text{m}}^{\text{E}} \), are the following. (i) Breaking of the structure of one or both of the components in a solution, i.e. the loss of dipolar association between the molecules (dispersion forces). (ii) The geometry of molecular structures which does not favor the fitting of molecules of one component into the voids created by the molecules of other component. (iii) Steric hindrance of the molecules. The negative values of \( V_{\text{m}}^{\text{E}} \) are due to strong specific interactions such as (iv) association of molecules through the formation of hydrogen bonds or association due to dipole–dipole interactions, or (v) the accommodation of molecules due to considerable differences in molar volumes. The variations of the excess molar volumes in the present investigation are negative over the entire mole fraction range [28]. The presence of strong interaction is due to the hydrogen bonding (O···H–O–) between the carbonyl group (–C=O) of amide molecules and the hydroxyl group (–OH) of alcohol molecules. When the third component PA is added to the equimolar mixture, the existing hydrogen bond between amide and alcohol groups is broken and a new hydrogen bond is formed between unlike molecules of acid and alcohol. Moreover, all of the components of the liquid mixtures studied are polar in nature having dipole moments of: methanol μ = 1.70 D [6], ethanol μ = 1.69 D [6], 1-propanol μ = 1.58 D [6], N,N-dimethyl formamide μ = 3.82 [6], and propanoic acid μ = 1.75 [6]. Therefore, dipole–dipole interactions are also present in the investigated liquid mixtures. In addition to these effects, physical interactions such as geometrical fitting of smaller molecules into the voids created by the larger molecules is also favorable for the present systems.

Fig. 1
figure 1

Variation of the excess molar volume, \( V_{\text{m}}^{\text{E}} \), with the mole fraction of PA, x 1, of (DMF + MOH) + PA mixtures at T/K = 303.15 (filled circles), 313.15 (filled squares), and 323.15 (filled triangles)

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Fig. 2
figure 2

Variation of the excess molar volume, \( V_{\text{m}}^{\text{E}} \), with the mole fraction of PA, x 1, of (DMF + EOH) + PA mixtures at T/K = 303.15 (filled circles), 313.15 (filled squares), and 323.15 (filled triangles)

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Fig. 3
figure 3

Variation of the excess molar volume, \( V_{\text{m}}^{\text{E}} \), with the mole fraction of PA, x 1, of (DMF + POH) + PA mixtures at T/K = 303.15 (filled circles), 313.15 (filled squares), and 323.15 (filled triangles)

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Fig. 4
figure 4

Variation of the deviation in viscosity, Δη, with the mole fraction of PA, x 1, of (DMF + MOH) + PA mixtures at T/K = 303.15 (filled circles), 313.15 (filled squares), and 323.15 (filled triangles)

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Fig. 5
figure 5

Variation of the deviation in viscosity, Δη, with the mole fraction of PA, x 1, of (DMF + MOH) + PA (filled circles), (DMF + EOH) + PA (filled squares), and (DMF + POH) + PA (filled triangles) mixtures at T/K = 313.15

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Fig. 6
figure 6

Variation of the excess Gibbs energy of activation of viscous flow, ΔG *E, with the mole fraction of PA, x 1 of (DMF + MOH) + PA (filled circles), (DMF + EOH) + PA (filled squares), and (DMF + POH) + PA (filled triangles) mixtures at T/K = 323.15

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From Figs. 1, 2 and 3 it is observed that, as the temperature of the systems increases excess molar volumes become less negative, indicating a decrease of the interactions between the unlike molecules, but the interactions increase from MOH to POH. As the alkanol chain length increases, thereby decreasing the concentration of –OH groups in higher alkanols, it lowers the overall dipole moment, which causes weaker interactions. These are expected results. We have observed that the strength of interaction increases as we move from MOH to POH. This is due to the predominance of physical interactions over chemical interactions between the unlike molecules. In other words, geometrical fitting of smaller molecules into the voids created by the larger molecules among the molecular components of liquid mixtures. Similar studies were reported by Kumar et al. [29]. The strength of interactions in the mixtures follows the order (DMF + MOH) + PA < (DMF + EOH) + PA < (DMF + POH) + PA. The above discussion is also supported by the observed positive values of Δη and ΔG *E. Generally, negative values of Δη indicate the presence of dispersion forces or mutual loss of specific interactions among like molecules in the systems, due to weak intermolecular interactions, while positive values of the deviation in viscosity indicate the presence of strong interactions [30, 31]. The sign and magnitude of Δη depends on the combined effect of factors such as molecular size, shape, and intermolecular forces. From the above observations it is clear that, as the temperature increases, the interaction between unlike molecules decreases.

The partial molar volumes \( \overline{V}_{{{\text{m}},1}} \) of component 1 (propanoic acid) and \( \overline{V}_{{{\text{m}},2}} \) of component 2 (N,N-dimethyl formamide + methanol/ethanol/1-propanol) in the mixtures, over the entire composition range, were calculated by using the following relations [32]:

$$ \overline{V}_{{{\text{m}},1}} = V_{\text{m}}^{\text{E}} + V_{1}^{*} + x_{2} \left( {\frac{{\partial V_{\text{m}}^{\text{E}} }}{{\partial x_{1} }}} \right)_{T,p} $$
(6)
$$ \overline{V}_{{{\text{m}},2}} = V_{\text{m}}^{\text{E}} + V_{2}^{*} - x_{1} \left( {\frac{{\partial V_{\text{m}}^{\text{E}} }}{{\partial x_{1} }}} \right)_{T,p} $$
(7)

The derivatives \( \left( {\frac{{\partial V_{\text{m}}^{\text{E}} }}{{\partial x_{1} }}} \right)_{T,p} \) in Eqs. 6 and 7 were obtained by differentiating Eq. 4, which leads to the following equations for \( \overline{V}_{{{\text{m}},1}} \) and \( \overline{V}_{{{\text{m}},2}} \):

$$ \overline{V}_{m,1} = V_{1}^{*} + x_{2}^{2} \sum\limits_{i = 0}^{j} {A_{i} \left( {x_{2} - x_{1} } \right)^{i} - 2x_{1} x_{2}^{2} } \sum\limits_{i = 1}^{j} {A_{i} \left( {x_{2} - x_{1} } \right)^{i - 1} } $$
(8)
$$ \overline{V}_{m,2} = V_{2}^{*} + x_{1}^{2} \sum\limits_{i = 0}^{j} {A_{i} \left( {x_{2} - x_{1} } \right)^{i} - 2x_{1}^{2} x_{2} } \sum\limits_{i = 1}^{j} {A_{i} \left( {x_{2} - x_{1} } \right)^{i - 1} } $$
(9)

Here j is an integer taking the value of 4; using the above equations, \( \overline{V}_{\text{m,1}}^{\text{E}} \) and \( \overline{V}_{\text{m,2}}^{\text{E}} \) have been evaluated using:

$$ \overline{V}_{\text{m,1}}^{\text{E}} = \overline{V}_{{{\text{m}},1}} - V_{1}^{ * } $$
(10)
$$ \overline{V}_{\text{m,2}}^{\text{E}} = \overline{V}_{{{\text{m}},2}} - V_{2}^{ * } $$
(11)

The values of \( \overline{V}_{{{\text{m}},1}} \) and \( \overline{V}_{{{\text{m}},2}} \) are reported in Table 6. The variations of excess partial molar volumes, \( \overline{V}_{\text{m,1}}^{\text{E}} \) and \( \overline{V}_{\text{m,2}}^{\text{E}} \), with mole fraction of PA are shown in Figs. 7, 8, 9. From the above table, it can be seen that the values of \( \overline{V}_{\text{m,1}} \) and \( \overline{V}_{{{\text{m}},2}} \) for both components in the mixtures are less than their respective molar volumes in the pure state. From Figs. 7, 8 and 9 it is seen that the excess partial molar volumes are almost always negative over the entire composition range. This suggest that a contraction of volume occurs in the binary mixtures, indicating the presence of strong interactions between unlike molecules of the mixtures as observed for \( V_{\text{m}}^{\text{E}} \).

Table 6 Partial molar volumes as a function of the mole fraction of PA, x 1, of all the liquid mixtures at T/K = 303.15, 313.15 and 323.15 (the mole fractions of DMF and MOH/EOH/POH are equal)
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Fig. 7
figure 7

Variation of the excess partial molar volumes \( \overline{V}_{\text{m,1}}^{\text{E}} \) (solid lines), \( \overline{V}_{\text{m,2}}^{\text{E}} \) (dashed lines) with the mole fraction of PA, x 1, of (DMF + MOH) + PA mixtures at T/K = 303.15 (filled circles), 313.15 (filled squares), and 323.15 (filled triangles)

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Fig. 8
figure 8

Variation of the excess partial molar volumes \( \overline{V}_{\text{m,1}}^{\text{E}} \) (solid lines), \( \overline{V}_{\text{m,2}}^{\text{E}} \) (dashed lines) with the mole fraction of PA, x 1, of (DMF + EOH) + PA mixtures at T/K = 303.15 (filled circles), 313.15 (filled squares), and 323.15 (filled triangles)

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Fig. 9
figure 9

Variation of the excess partial molar volumes \( \overline{V}_{\text{m,1}}^{\text{E}} \) (solid lines), \( \overline{V}_{\text{m,2}}^{\text{E}} \) (dashed lines) with the mole fraction of PA, x 1, of (DMF + POH) + PA mixtures at T/K = 303.15 (filled circles), 313.15 (filled squares), and 323.15 (filled triangles)

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The partial molar volumes and excess partial molar volumes of the components at infinite dilution, \( \overline{V}_{{{\text{m}},1}}^{\infty } ,\;\overline{V}_{{{\text{m}},2}}^{\infty } ,\;\overline{V}_{{{\text{m}},1}}^{{{\text{E}},\infty }} \) and \( \overline{V}_{\text{m,2}}^{{{\text{E,}}\infty }} \), respectively, were obtained by putting x = 0 in Eq. 8 and x = 1 in Eq. 9:

$$ \overline{V}_{\text{m,1}}^{{{\text{E,}}\infty }} = A_{0} + A_{1} + A_{2} + A_{3} + \ldots \ldots = \overline{V}_{{{\text{m,}}1}}^{\infty } - V_{1}^{ * } , $$
(12)
$$ \overline{V}_{\text{m,2}}^{{{\text{E,}}\infty }} = A_{0} - A_{1} + A_{2} - A_{3} + \ldots \ldots = \overline{V}_{\text{m,2}}^{\infty } - V_{2}^{ * } , $$
(13)

The pertinent values of \( \overline{V}_{{{\text{m}},1}}^{\infty } \), \( \overline{V}_{{{\text{m}},2}}^{\infty } \), \( \overline{V}_{\text{m,1}}^{{{\text{E,}}\infty }} \) and \( \overline{V}_{\text{m,2}}^{{{\text{E,}}\infty }} \) are reported in Table 7. From this table it is seen that these values are negative, from which we conclude that strong interactions exist among the unlike molecules of the mixtures. The magnitude of the excess partial molar volumes at infinite dilution also follow the order (DMF + POH) + PA > (DMF + EOH) + PA > (DMF + MOH) + PA, which supports the trends of \( V_{\text{m}}^{\text{E}} \) values observed in these mixtures.

Table 7 Values of \( \overline{V}_{{{\text{m}},1}}^{\infty } \), \( V_{1}^{ * } \), \( \overline{V}_{{{\text{m}},1}}^{{{\text{E}},\infty }} \), \( \overline{V}_{{{\text{m}},2}}^{\infty } \), \( V_{2}^{ * } \), and \( \overline{V}_{{{\text{m}},2}}^{{{\text{E}},\infty }} \) for all of the liquid mixtures at T/K = 303.15, 313.15 and 323.15
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The dynamic viscosities of the binary liquid mixtures have been calculated using the following empirical relations. The Grunberg and Nissan [33] model is based on the Arrhenius equation for the viscosity of liquid mixtures,

$$ { \ln }\eta = x_{1} { \ln }\eta_{1} + x_{2} { \ln }\eta_{2} + x_{1} x_{2} G_{12} $$
(14)

where G 12 is an interaction parameter that is a function of components 1 and 2 as well as temperature. Hind and Ubbelohde [34] suggested an equation for the viscosity of binary liquid mixtures as

$$ \eta = x_{1}^{2} \eta_{1} + x_{2}^{2} \eta_{2} + 2x_{1} x_{2} H_{12} $$
(15)

where H 12 is an interaction parameter that is attributed to unlike pair interactions. Katti and Chaudari [35] proposed the following equation

$$ \ln (\eta V) = x_{1} \ln \left( {\eta_{1} V_{1} } \right) + x_{2} \ln \left( {\eta_{2} V_{2} } \right) + x_{1} x_{ 2} W_{\text{vis}} /RT $$
(16)

where W vis is an interaction term. Heric and Brewer [36] derived the relation

$$ \ln \eta = x_{1} \ln \eta_{1} + x_{2} \ln \eta_{2} + x_{1} \ln M_{1} + x_{2} \ln M_{2} - \ln \left( {x_{1} M_{1} + x_{2} M_{2} } \right) + x_{1} x_{2} \Updelta_{12} $$
(17)

where Δ12 is the interaction term.

In the above equations, η 1, η 2, M 1, and M 2 are the viscosities and molar masses of the pure components of PA and (DMF + MOH/EOH/POH), respectively. The theoretical values of viscosity of the liquid mixtures calculated using the above equations are compiled in Table 8. Table 9 presents the values of the interaction parameters along with the standard deviations, σ. The adjustable parameters G 12, H 12, W vis and Δ12 represent binary interactions. The variation of these parameters with composition follows the order (DMF + POH) + PA > (DMF + EOH) + PA > (DMF + MOH) + PA at constant temperature. Further, the interaction parameter values decrease with an increase in temperature for all of the systems studied. These results are in good agreement with the results derived from the excess properties. Prolongo et al. [37] reported positive values of interaction parameters corresponding to systems with negative excess molar volumes. This is consistent with our results. Among all of these models, the viscosity representations obtained from the Katti and Chaudhari model are in best agreement with the experimental viscosity data.

Table 8 Calculated values of viscosity, η (×10−3, N s m−2), with mole fraction of PA, x 1, for all of the systems at T/K = 303.15, 313.15 and 323.15 (the mole fractions of DMF and MOH/EOH/POH are equal)
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Table 9 Various interaction parameters calculated from Eqs. 14–17 and the corresponding standard deviations, σ (×10−3, N s m−2) for all of the liquid mixtures at T/K = 303.15, 313.15 and 323.15
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4 Conclusion

The densities and viscosities of liquid mixtures of propanoic acid with equimolar mixtures of N,N-dimethyl formamide and methanol/ethanol/1-propanol have been measured over the entire composition range at T/K = 303.15, 313.15, and 323.15. The parameters \( V_{\text{m}}^{\text{E}} ,\;\Updelta \eta ,\;\Updelta G^{{ * {\text{E}}}} ,\;\overline{V}_{{{\text{m}},1}} ,\;\overline{V}_{{{\text{m}},2}} ,\;\overline{V}_{\text{m,1}}^{\text{E}} \) and \( \overline{V}_{\text{m,2}}^{\text{E}} \) have been computed from the experimental results. The values of \( V_{\text{m}}^{\text{E}} \) are negative whereas Δη and ΔG *E are positive at all studied temperatures, indicating the presence of strong interactions such as hydrogen bonding (O···H–O–) and interactions between the carbonyl group (–C=O) of amide molecules and the hydroxyl group (–OH) of alcohol groups, and also intermolecular interactions between the carbonyl group (–C=O) of acid molecules and hydroxyl group (–OH) of alcohols, dipole–dipole interactions, and geometrical fitting of smaller molecules into the voids created by the larger. These deviations and excess properties have been fitted with a Redlich–Kister type polynomial. The strength of interactions follows the order (DMF + MOH) + PA < (DMF + EOH) + PA < (DMF + POH) + PA. The calculated values of the partial molar volumes have also been examined, indicating the existence of strong interactions among unlike molecules in the mixtures. The strength of interactions was also studied using the variation of these properties with temperature. The experimental viscosity values were compared with the viscosity values obtained from different empirical relations.