University of Łódź, Department of Physical Chemistry of Solutions, Łódź, Pomorska 163, Poland

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1 Int. J. Electrchem. Sci., 9 (2014) Internatinal Jurnal f ELECTROCHEMICAL SCIENCE Cnductmetric Studies f 1-Ethyl-3-methylimidazlium Tetraflurbrate and 1-Butyl-3-methylimidazlium Tetraflurbrate in 1-Prpanl at Temperatures frm ( t ) K Agnieszka Bruń *, Adam Bald University f Łódź, Department f Physical Chemistry f Slutins, Łódź, Pmrska 163, Pland * chmielewska.a@gmail.cm Received: 15 January 2014 / Accepted: 7 February 2014 / Published: 23 March 2014 The electrical cnductances f dilute slutins f the inic liquids 1-ethyl-3-methylimidazlium tetraflurbrate [emim][bf 4 ] and 1-butyl-3-methylimidazlium tetraflurbrate [bmim][bf 4 ] in 1- prpanl have been measured in the temperature range frm ( t ) K at 5 K intervals. The inic assciatin cnstant, K A, limiting mlar cnductances,, and distance parameters, R, were btained using the lw cncentratin Chemical Mdel (lccm). The examined electrlytes are strngly assciated in 1-prpanl in the whle temperature range. Frm the temperature dependence f the limiting mlar cnductivities the Eyring s activatin enthalpy f charge transprt was estimated. The thermdynamic functins such as Gibbs energy, entrpy, and enthalpy f the prcess f in pair frmatin were calculated frm the temperature dependence f the assciatin cnstants. Keywrds: cnductivity f inic liquids, 1-ethyl-3-methylimidazlium tetraflurbrate, 1-butyl-3- methylimidazlium tetraflurbrate, in assciatin, thermdynamic functins 1. INTRODUCTION The data f physical and chemical prperties n inic liquids (ILs) are essential fr bth theretical research and industrial applicatin. A survey f literature indicates that physical prperties f pure inic liquids have been studied extensively, but the thermphysical and thermdynamic prperties f the mixtures f ILs with aqueus r rganic slvents, have nt been studied in a systematic way s far. The transprt prperties f the mixtures f inic liquids (cnductance, viscsity, and transference numbers) are imprtant because the values prvide useful and sensitive infrmatin abut in-slvent interactin, in-in assciatin, and slvent structure. Such studies allw the

2 Int. J. Electrchem. Sci., Vl. 9, predictin f ILs in specific applicatins such as active pharmaceutical ingredients, high energy batteries r ther electrchemical systems and chemical reactins [1-10]. The mst intensively investigated ILs are thse with imidazlium catin, but very little cnductivity studies cncerned the inic assciatin f ILs in mlecular slvents [11-22]. Frm these papers results that the alkyl chain length f the catin, type f anin, and physical prperties f the mlecular slvents affect the inic assciatin cnstants. The inic liquids are slvated t a different extent by the slvents, and the inic assciatin depends significantly n the in slvatin [21]. Slight inic assciatin f ILs ccurs in the water, N,N-dimethylfrmamide, acetnitrile, methanl and ethanl, whereas it becmes significant in the alchls (1-prpanl, 2-prpanl, 1-butanl, and 1- pentanl). In fact similar t the classical electrlytes, the ln K A values f the ILs were fund t increase linearly with the reverse f the dielectric cnstants f the slvents, which indicates that the electrstatic interactin between the ins are predminant fr the inic assciatin f the ILs [11]. Therefre, we decided t study the inic assciatin and slvatin behavir f inic liquids in varius slvents as a functin f the temperature. Fr this purpse, in ur previus paper [22], we have reprted the results f the cnductance measurements f 1-ethyl-3-methylimidazlium tetraflurbrate [emim][bf 4 ] and 1-butyl-3-methylimidazlium tetraflurbrate [bmim][bf 4 ] slutins in N,N-dimethylfrmamide. Imidazlium inic liquids were chsen because f their thermal and chemical stability and the insignificant impact f air and misture. Slight in assciatin was fund fr the inic liquids in this diplar aprtic slvent (ε r = at K [23]) in the whle investigated temperature range. There are n experimental values f the cnductmetric data available in the literature abut ILs tested by us, in such prtic slvent as 1-prpanl (ε r = at K [24]) at varius temperatures. Cntinuing ur studies n electrical cnductivity f ILs, in this wrk, precise cnductivity measurements have been carried ut in dilute slutins f [emim][bf 4 ] and [bmim][bf 4 ] in 1-PrOH at temperatures range (283.15K ) K and at atmspheric pressure. The btained data were used t calculate the values f the limiting mlar cnductances,, and the assciatin cnstants, K A n the basis f lccm mdel. The Gibbs energy,, enthalpy,, and entrpy,, f in pair frmatin as well as the Eyring activatin enthalpy f charge transprt, have been evaluated. 2. EXPERIMENTAL 2.1. Reagents and chemicals The specificatins f used chemicals are summarized in Table 1. Table 1. Specificatin f chemical samples H A S A H, fr the electrlytes chemical name surce initial mass fractin purity purificatin methd final water mass fractin 1-PrOH Aldrich nne a [emim][bf 4 ] Fluka nne < a < b [bmim][bf 4 ] Fluka nne < a < b

3 Int. J. Electrchem. Sci., Vl. 9, a Manufacturer s analysis. b Our analysis (Karl Fischer culmetric titratin) Apparatus All the slutins were prepared by mass using an analytical balance (Sartrius RC 210D) with a precisin f g. The measurement prcedure was based n the methd described by Bešter-Rgač et al. [18, 25] and used by us in ur previus wrks [22, 26]. Cnductivity measurements were perfrmed with a three-electrde cell with the use f a Precise Cmpnent Analyser type 6430B (Wayne-Kerr, UK) under argn atmsphere and at the different frequencies, ν, (0.2, 0.5, 1, 2, 3, 5, 10, 20) khz. The temperature was kept cnstant within K (Calibratin Thermstat Ultra UB 20F with Thrughflw cler DLK 25, Lauda, Germany). The details f the experimental prcedure fr cnductmetric measurements were described in ur previus paper [22]. The uncertainty f the measured values f cnductivity was 0.03 %. Densities were measured with an Antn Paar DMA 5000 scillating U-tube densimeter equipped with a thermstat with a temperature stability within K. The densimeter was calibrated with extra pure water, previusly degassed ultrasnically. The uncertainty f the density is ± g cm -3. Viscsities were measured with a AVS 350 device (Schtt Instruments, Germany). The Ubbelhde viscsimeter filled with the liquid was placed vertically in a thermstat water. An ptelectrnic stpwatch with a precisin f 0.01 s was used fr flw time measurements. The temperature was kept cnstant using a precisin thermstat HAAKE DC30 (Therm Scientific). The accuracy f temperature cntrl was 0.01 K. The uncertainty in the viscsity measurements was better than 0.05%. 3. RESULTS AND DISCUSSION Table 2. Densities, ρ, viscsities, η, and relative permittivities, ε r, f 1-prpanl at different temperatures T/K ρ / g cm -3 /mpa s ε r

4 Int. J. Electrchem. Sci., Vl. 9, Table 3. Mlar cnductances,, crrespnding mlalities, m, and density gradients, b, fr slutins f [emim][bf 4 ] and [bmim][bf 4 ] in 1-PrOH ver the temperature range frm ( t ) K ml kg - 1 S cm 2 ml -1 ml kg -1 S cm 2 ml -1 ml kg -1 S cm 2 ml -1 ml kg -1 S cm 2 ml -1 [emim][bf 4 ] T = K T = K T = K T = K b = kg 2 dm -3 ml -1 b = kg 2 dm -3 ml -1 b = kg 2 dm -3 ml -1 b = kg 2 dm -3 ml T = K T = K T = K T = K b = kg 2 dm -3 ml -1 b = kg 2 dm -3 ml -1 b = kg 2 dm -3 ml -1 b = kg 2 dm -3 ml [bmim][bf 4 ]] T = K T = K T = K T = K b = kg 2 dm -3 ml -1 b = kg 2 dm -3 ml -1 b = kg 2 dm -3 ml -1 b = kg 2 dm -3 ml

5 Int. J. Electrchem. Sci., Vl. 9, Table 3. (cntinued) ml kg - 1 S cm 2 ml -1 ml kg -1 S cm 2 ml -1 ml kg -1 S cm 2 ml -1 ml kg -1 S cm 2 ml -1 T = K T = K T = K T = K b = kg 2 dm -3 ml -1 b = kg 2 dm -3 ml -1 b = kg 2 dm -3 ml -1 b = kg 2 dm -3 ml The densities, viscsities, and relative permittivities f 1-prpanl as a functin f temperature are listed in Table 2. The values f relative permittivities were btained by interplatin frm ur [27-30] and literature data [31, 32]. The values f densities and viscsities shw a very gd agreement with literature [24, 32, 33]. T cnvert mlnity, m ~, (mles f electrlyte per kilgram f slutin) int mlarity, c, the values f density gradients, b, have been determined independently and used in the equatin c / m ~ = ρ = ρ + b m ~ (1a) where ρ is the density f the slvent. Mlar cncentratins, c, were necessary t use the cnductivity equatin. The density gradients and the mlar cnductances f the ILs in slutin,, as a functin f IL mlality, m, (mles f electrlyte per kilgram f slvent) and temperature are presented in Table 3. The relatinship amng m,, and c is the fllwing = c/ρ = 1 / (1 + mm) (1b) where M is the mlar mass f electrlyte. The plt f mlar cnductances,, versus the square rt f the mlar cncentratin, c 1/2, fr the investigated systems mntnically decreases as shwn in Figures 1 and 2.

6 Int. J. Electrchem. Sci., Vl. 9, /S cm 2 ml K K c 1/2 /(ml dm -3 ) 1/2 Figure 1. Mlar cnductance,, f [emim]bf 4 slutins in 1-PrOH versus c 1/2 at experimental temperatures;, K;, K;, K; +, K; ӿ, K;, K;, K;, K. The lines represent the calculatins accrding t Eqs (2) thrugh (4). 50 /S cm 2 ml K K c 1/2 /(ml dm -3 ) 1/2 Figure 2. Mlar cnductance,, f [bmim]bf 4 slutins in 1-PrOH versus c 1/2 at experimental temperatures;, K;, K;, K; +, K; ӿ, K;, K;, K;, K. The lines represent the calculatins accrding t Eqs (2) thrugh (4). The cnductivity data were analyzed in the framewrk f the lw cncentratin Chemical Mdel (lccm) [34]. This apprach uses the set f equatins = α [ S(αc) 1/2 + E(αc)ln(αc) + J(αc) + J 3/2 (αc) 3/2 ] (2) K A = (1 α) / (α 2 cy ± 2 ) (3) and

7 Int. J. Electrchem. Sci., Vl. 9, ln y ± = ( Aα 1/2 c 1/2 ) / (1 + BRα 1/2 c 1/2 ) (4) In these equatins, is the limiting mlar cnductance; α is the dissciatin degree f an electrlyte; K A is the inic assciatin cnstant; R is the distance parameter f ins; y ± is the activity cefficient f ins n the mlar scale; A and B are the Debye Hückel equatin cefficients. The analytical frm f the parameters S, E, J, and J 3/2 was presented previusly [34]. The values f, K A, and R were btained using the well-knwn prcedure given by Fuss [35] and are cllected in Table 4. Table 4. Limiting mlar cnductances,, assciatin cnstants, K A, distance parameters, R, and standard deviatins, σ(), fr the investigated inic liquids in 1-PrOH at different temperatures a T/K /S cm 2 ml -1 K A /dm 3 ml -1 R/nm σ() [emim][bf 4 ] ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± [bmim][bf 4 ] ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± As seen frm Table 4, bth inic liquids are highly assciated. Fr mlar cncentratins f abut ml dm -3, half f the examined electrlytes ccurs in the undissciated frm in 1- prpanl. In the case f the same inic liquids slutins in DMF, the assciatin cnstants are practically negligible and ne can assume that these electrlytes exist essentially as free ins [22]. Therefre, it is pssible that an essential rle in the inic assciatin prcess plays the relative permittivity f the slvent. The linear dependence f ln K A = f (1/ε r ), shwn in Figure 3, suggest that the electrstatic interactins between ins are mainly respnsible fr their assciatin.

8 Int. J. Electrchem. Sci., Vl. 9, lnk A /ɛ r Figure 3. Plt f the lgarithm f the assciatin cnstant fr the, [emim][bf 4 ]; and, [bmim][bf 4 ] versus the reciprcal f the relative permittivity f 1-PrOH. The data cllected in Table 4 als shw that the inic assciatin phenmenn increases with increasing temperature, and the effect is much mre prnunced in the case f [bmim][bf 4 ]. In the case f DMF slutins, the assciatin cnstants were small and slightly higher fr [emim][bf 4 ], but they increase with increasing temperature t a similar extent. These facts prve that the in-pairing prcess des nt depend nly n the dielectric prperties f the slvent. An imprtant rle play the in-slvent interactins and the size f the alkyl substituent in the imidazlium catin. One shuld als pay attentin t the fact that the temperature dependences f R values in the in pairs have a different character fr bth investigated inic liquids, ie, in the case f [emim][bf 4 ] the values f R increase, and in the case f [bmim][bf 4 ] they decrease with increasing temperature. This may explain why in the case f [bmim][bf 4 ] the K A values increase mre intensively with increasing temperature. The limiting mlar cnductances increase as the temperature increases since the mbility f free ins is higher. Hwever, the values f fr [emim][bf 4 ] are higher frm thse values fr [bmim][bf 4 ]. This indicates that the values decrease with increasing alkyl chain length f the ILs. Furthermre, the differences between the values fr bth inic liquids increase with increasing temperature, frm abut 0.6 units (at K) t abut 2.1 units (at K). In the case f aprtic DMF the values f were als higher fr [emim][bf 4 ]. Hwever, the differences between the values fr bth inic liquids practically did nt depend n the temperature, and they were abut units [22]. This may mean that the effect f temperature n the in-pairing prcess and n the mbility f ins may depend n the alkyl chain length f the ILs and the in-slvent interactins. The limiting mlar cnductances fr [emim][bf 4 ] and [bmim][bf 4 ] presented in Table 4 are abut three times smaller than thse values determined in DMF. The simple hydrdynamic mdels assume that the values f limiting mlar cnductance,, and macrscpic viscsity f the slvent,, are ffset and the Walden prduct value, η, shuld be independent f temperature. The values presented in Table 5 shw that fr examined inic liquids the Walden rule is well fulfilled bth in 1-

9 Int. J. Electrchem. Sci., Vl. 9, prpanl as well as in N,N-dimethylfrmamide. It can als be nted that the values f η are much smaller in the case f 1-prpanl. The same simple thermdynamic mdels assume that the η values are reciprcally prprtinal t the effective size f ins accrding t the equatin η = cnst / r s. Therefre, it can be assumed that the effective size f ins in 1-PrOH are much greater than in DMF. It is pssible that this - is due t the pr slvatin f BF 4 anins in an aprtic DMF cmpared with a prtic 1-PrOH. - Althugh the crystallgraphic radius f BF 4 in is slightly larger than the Br - and Cl -, the values f limiting mlar cnductivities fr these ins in DMF are very similar. The fact that the little plarized anins are pr slvated in diplar aprtic slvents seems t be fairly well substantiated [36-39]. Hwever, the evaluatin f effective size f ins [emim] +, [bmim] +, and BF - 4 requires determining the limiting inic cnductivities values using the prcedures applied in ur previus wrk [26]. On the basis f data presented in Tables 4 and 5, respectively, it can be cncluded that the limiting inic cnductivities,, and thus the inic Walden prducts,, fr [emim] + are higher than thse fr [bmim] +, bth in 1-PrOH and in DMF. Frm Table 5 it fllws that the differences between the values f fr [emim] + and [bmim] + with increasing temperature increase slightly in the case f 1-PrOH (frm t 0.026), and decrease slightly (frm t 0.030) in the case f DMF. Table 5. Cmparisn f the Walden prduct η, as a functin f temperature fr the investigated inic liquids in 1-PrOH and DMF [26]. T/K 10-2 η/scm 2 ml 1 mpa s [emim][bf 4 ] + 1-PrOH [bmim][bf 4 ] + 1-PrOH [emim][bf 4 ] + DMF [bmim][bf 4 ] + DMF Frm the temperature dependence f, the Eyring activatin enthalpy f charge transprt, H, was btained ln + 2/3 ln ρ = H RT + D (5) where D is an empirical cnstant. Frm the slpe f the linear functin f ln + 2/3 ln ρ versus the inverse f the temperature (1/T), which is shwn in Figure 4, we btained H values. H values are J ml -1 and J ml -1 fr [emim][bf 4 ] and [bmim][bf 4 ], respectively. Fr [bmim][bf 4 ], the value f H is thus higher by 330 units. In the case f aprtic DMF the H values

10 Int. J. Electrchem. Sci., Vl. 9, were 8541 J ml -1 and 8669 J ml -1 fr [emim][bf 4 ] and [bmim][bf 4 ], respectively [22]. Thus, fr [bmim][bf 4 ], the value f H was als higher, but nly by 128 units. It is the result f the presence f a larger substituent in the [bmim] + catin cmpared t [emim] +. It seems that this cnclusin applies t bth prtic 1-prpanl and aprtic N,N-dimethylfrmamid. ln + 2/3lnρ (T /K) -1 Figure 4. Plt f ln + 2/3 ln ρ as a functin f 1/T fr, [emim][bf 4 ]; and, [bmim][bf 4 ] in 1- PrOH. The temperature dependence f the assciatin cnstant was used t calculatin f Gibbs free energy f in frmatin, (T)= RT ln K A (T) (6) (T) can als be expressed by the plynmial (T) = A + A 1 T + A 2 T 2 (7) The values f parameters A, A 1, and summarized in Table 6. A 2 f Eq. (7) and crrelatin cefficients, r 2, are Table 6. Cefficients f Eq. (7) and crrelatin cefficients, r 2, fr [emim][bf 4 ] and [bmim][bf 4 ] in 1-PrOH A /kj ml -1 A 1 /J ml -1 K -1 A 2 /J ml -1 K -2 r 2 [emim][bf 4 ] [bmim][bf 4 ]

11 Int. J. Electrchem. Sci., Vl. 9, The entrpy and enthalpy f in assciatin are defined as G A S A = T p = A 1 2A 2 T (8) H A = + T S A = A A 2 T 2 (9) The thermdynamic functins f the in pair frmatin (, temperatures are presented in Table 7 and in Figures 5, 6, and 7, respectively., S A H A ) at different Table 7. Thermdynamic functins f assciatin f [emim][bf 4 ] and [bmim][bf 4 ] slutins in 1- PrOH at different temperatures S A H A T/K J ml -1 J ml -1 K -1 J ml -1 [emim][bf 4 ] [bmim][bf 4 ]

12 Int. J. Electrchem. Sci., Vl. 9, T/ K Δ / J ml Figure 5. Variatin f Gibbs free energy,, [bmim][bf 4 ] in 1-PrOH., as a functin f temperature T f, [emim][bf 4 ]; and ΔS A / J ml -1 K T/ K Figure 6. Variatin f assciatin entrpies,, [bmim][bf 4 ] in 1-PrOH. S A, as a functin f temperature f, [emim][bf 4 ]; and The values f presented in Table 7 and Figure 5 indicate that the spntaneity f the in pair frmatin at K is cmparable fr bth salts examined. With increasing temperature the spntaneity f the in pair frmatin becmes smaller in the case f salt cntaining the smaller catin, ie [emim][bf 4 ]. The differences between values f at K, hwever, des nt exceed 300 J, which represents nly abut 1.7 % f the free enthalpy f assciatin value. One shuld pay attentin that in the case f [emim][bf 4 ] and [bmim][bf 4 ] w N,N-dimethylfrmamide the situatin was reversed, ie the spntaneity f the inic assciatin was smewhat higher fr salt cntaining the smaller catin, ie [emim][bf 4 ] [22]. Hwever, in this case, the K A values are very small (abut 10 units), and the differences between the K A values fr bth the salts are very small and d nt exceed

13 Int. J. Electrchem. Sci., Vl. 9, the unit. Fr example, using different cnductance equatins can btain cmparable r even greater differences between values f the assciatin cnstant ΔH A / J ml T/ K Figure 7. Variatin f enthalpies, [bmim][bf 4 ] in 1-PrOH. H A, as a functin f temperature f, [emim][bf 4 ]; and, The increase f temperature leads t mre negative values, which means shifting the equilibrium twards the frmatin f in pairs. As can be seen in Figures 6 and 7, bth the values f entrpy and enthalpy f assciatin are psitive and greater fr [bmim][bf 4 ]. Mrever, the values f and slightly decrease with increasing temperature fr bth tested electrlytes. Psitive S A H A values f entrpy prve that the transitin frm the free slvated ins int the in pairs causes that system becmes less rdered. It is pssible that this is related t the partial deslvatin f ins prir t the frmatin f in pair. This effect is mre prnunced in the case f [bmim][bf 4 ]. The psitive values f indicate that the in pair frming prcesses are endthermic, particularly in the case f H A [bmim][bf 4 ]. Frm Eq. (10) (T) = (T) T H A S A (T) (10) it fllws that entrpic effects seem t dminate ver the enthalpic effects, because the Gibbs free energy,, is negative, and thus the in pair frmatin is exergic in bth cases. 4. CONCLUSIONS Mlar cnductances f slutins f inic liquids, [emim][bf 4 ] and [bmim][bf 4 in 1-prpanl have been reprted at T = ( t ) K. Analyses f the cnductivity data n the basis f Barthel s lw cncentratin Chemical Mdel (lccm) prvided imprtant infrmatin abut the in assciatin f investigated inic liquid slutins. Bth examined inic liquids behave like classical electrlytes in slvent with lw dielectric cnstant, and the electrstatic interactins between ins is mainly respnsible fr their assciatin. A strng inic assciatin was bserved fr the ILs in prtic slvent 1-PrOH at all experimental temperatures. The K A values increase as the temperature increases

14 Int. J. Electrchem. Sci., Vl. 9, (with decreasing relative permittivity f the slvent) and increase with an increase in the alkyl chain length f the ILs. The limiting mlar cnductances f ILs are influenced by the inic slvatin. The evaluated values f thermdynamic functins f assciatin suggest the spntaneity f the assciatin prcess. The values f are psitive and suggest that the in-pairing prcess is endthermic. H A Because the Gibbs free energy is negative, entrpic effects seem t dminate ver the enthalpic effects, and thus the in pair frmatin f inic liquids in 1-prpanl is exergic. References 1. W. L Hugh and R. D. Rgers, Bull. Chem. Sc. Jpn., 80 (2007) W. L. Hugh, M. Smiglak, H. Rdriguez, R. P. Swatlski, S. K. Spear, D. T. Daly, J. Pernak, J. E. Grisel, R. D. Carliss, M. D. Sutull, J. J. H. Davis and R. D. Rgers, New J. Chem., 31 (2007) D. R. MacFarlane, M. Frsyth, P. C. Hwlett, J. M. Pringle, J. Sun, G. Annat, W. Neil and E. I. Izgrdina, Acc. Chem. Res., 40 (2007) P. Wang, S. M. Zakeeruddin, J. E. Mser and M. Grӓtzel, J. Phys. Chem. B, 107 (2003) T. Weltn, Chem. Rev., 99 (1999) T. Weltn, Crd. Chem. Rev., 248 (2004) P. Wasserscheid and W. Keim, Angew. Chem., Int. Ed., 39 (2000) J. S. Wilkes, J. Ml. Catal. A: Chem., 214 (2004) N. V. Plechkva and K. R. Seddn, Chem. Sc. Rev., 37 (2008) F. Endres and S. Zein El Abedin, Phys. Chem. Chem. Phys., 8 (2006) H. Wang, J. Wang, S. Zhang, Y. Pei and K. Zhu, ChemPhysChem, 10 (2009) S. Katsuta, K. Imai, Y. Kud, Y. Takeda, H. Seki and M. Nakakshi, J. Chem. Eng. Data, 53 (2008) S. Katsuta, R. Ogawa, N. Yamaguchi, T. Ishitani and Y. Takeda, J. Chem. Eng. Data, 52 (2007) H. Shekaari and S. S. Musavi, Fluid Phase Equilib., 286 (2009) T. Nishida, Y. Tashir and M. Yamamt, J. Flurine Chem., 120 (2003) H. Shekaari and E. Armanfar, J. Chem. Eng. Data, 55 (2010) M. Bešter-Rgač, J. Hunger, A. Stppa and R. Buchner, J. Chem. Eng. Data, 55 (2010) M. Bešter-Rgač, J. Hunger, A. Stppa and R. Buchner, J. Chem. Eng. Data, 56 (2011) R. Jan, G. M. Rather and M. A. Bhat, J. Slutin Chem., 42 (2013) S. Gupta, A. Chatterjee, S. Das, B. Basu and B. Das, J. Chem. Eng. Data, 58 (2013) R. Sadeghi and N. Ebrahimi, J. Phys. Chem. B, 115 (2011) A. Bruń, and A. Bald, J. Chem. Eng. Data, 57 (2012) G. A. Krestv, V. N. Afanas ev, and L. S. Efremva, Fizik-khimicheskie svistva binarnykh rastvritelei (Physicchemical prperties f binary slvents), Leningrad: Khimiya (1988). 24. J. A. Riddick, W. B. Bunger and T. K. Sakan, Organic Slvents, Wiley, New Yrk (1986). 25. M. Bešter-Rgač and D. Habe, Acta Chim. Slv., 53 (2006) A. Bruń, and A. Bald, J. Chem. Eng. Data, 57 (2012) S. Taniewska-Osinska, A. Piekarska, A. Bald and Adam Szejgis, J. Chem. Sc., Faraday Trans. 1, 85 (1989) 3709.[27] 28. A. Chmielewska, M. Zurada, K. Klimaszewski and A. Bald, J. Chem. Eng. Data 54 (2009) K. Klimaszewski, A. Bald, R. J. Sengwa and S. Chudhary, Phys. Chem. Liq. 51 (2013) D. Chęcińska-Majak, A. Bald and R. J. Sengwa, J. Ml. Liq., 179 (2013) R. D. Bezman, E. F. Casassa and R. L. Kay, J. Ml. Liq., (1997) M. Gffredi and T. Shedlvsky, J. Phys. Chem., 71 (1967) 2176.

15 Int. J. Electrchem. Sci., Vl. 9, S. Pura, J. Ml. Liq., 136 (2007) J. M. G. Barthel, H. Krienke and W. Kunz, Physical chemistry f electrlyte slutins: mdern aspects, Springer, New Yrk (1998). 35. R. M. Fuss, J. Phys. Chem., 82 (1978) A. K. Cvingtn and T. Dickinsn, Physical chemistry f rganic slvent systems, Plenum Press, Lndn, New Yrk (1973). 37. J. E. Grdn, The rganic chemistry f electrlyte slutins, Wiley, New Yrk (1975). 38. A. J. Parker, Qiart. Rev. (Lndn), 16 (1962) B. G Cx, G.R. Hedwig, A. J. Parker and D. W. Wats, Austr. J. Chem, 27 (1974) The Authrs. Published by ESG ( This article is an pen access article distributed under the terms and cnditins f the Creative Cmmns Attributin license (