Ultrasonic, Density and Viscosity Studies in Binary Mixtures of Propylene Glycol and 1-Pentanol at Room Temperature

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2 Ultrasnic, Density and Viscsity Studies in Binary Mixtures f Prpylene Glycl and 1-Pentanl at Rm Temperature Ch. Swjanya and S. Sreehari Sastry * Department f Physics, Acharya Nagarjuna University, Nagarjunanagar -5225, India Abstract Speed f sund (U), Density (), and viscsity () values fr the binary mixture systems f Prpylene Glycl with 1-pentanl including thse f pure liquids were measured ver the entire mle fractin range at temperature K. Frm the experimentally determined values, therm-acustic parameters such as excess isentrpic cmpressibility (Ks ), excess mlar vlume (V ) and excess free length (Lf ) and excess enthalpy (H ) have been calculated. These results have been explained n the basis f intermlecular interactins between the cmpnents in the liquid mixture and crrelatins amng the parameters are discussed. Keywrds: Speed f sund, density, excess mlar vlume, isentrpic cmpressibility, free length, Prpylene Glycl 1. INTRODUCTION Speed f sund investigatins alng with the vlumetric and viscmetric studies f liquids and liquid mixtures are f cnsiderable imprtance and they play a significant rle in understanding the intermlecular interactins ccurring amng the cmpnent mlecules besides finding extensive applicatins in several industrial and technlgical prcesses [1, 2]. Several researchers [3-8] have measured the density, viscsity, and speed f sund fr a wide range f binary mixtures cntaining alchls as ne f the cmpnents, and these prperties were interpreted in terms f specific r nnspecific interactins. Alchls are strngly assciated in slutin because f diple-diple interactin and hydrgen bnding. They are f great imprtance fr their relevant rle in chemistry, bilgy and studies n hydrgen bnding in liquid mixtures. Alchls are als widely used as slvents. The mlecules cntaining OH grup frm assciative liquids due t hydrgen bnding. The effect shwn by the mlecules with ther functinal grups n these mlecules plays an imprtant rle in understanding the behavir f hydrgen bnding. The investigatins regarding the mlecular assciatin in liquid mixtures having armatic grup as ne f the cmpnents is f particular interest, since armatic grup is highly nn-plar and can assciate with any ther grup having sme degree f plar attractins. ven thugh cnsiderable wrk has been reprted n alchls as ne f the cmpnent in binary and ternary mixtures, the data n binary mixtures f Pentanl with Prpylene glycl at rm temperature (33 K) variatin is scanty. The study f thermdynamic prperties f multi cmpnent liquid mixtures and data n the analysis in terms f varius mdels are imprtant fr industrial and pharmaceutical applicatins [9]. The excess thermdynamic functins [] are sensitively dependent nt nly n the differences in intermlecular frces, but als n the differences in the size f the mlecules. The signs and magnitudes f these excess values can thrw light n the strength f interactins. S frm the experimentally determined values f speed f sund density and viscsity, varius therm-acustic parameters like excess isentrpic cmpressibility ( ), excess mlar vlume (V ), excess free length (L f ) and excess enthalpy (H ) have been calculated. Here we reprt the results and discuss excess therm-acustic parameters using the data regarding the speed f sund, density and viscsity fr the binary liquid mixtures f Prpylene glycl with 1-pentanl at temperature 33 K. II. XPRIMNTAL DTAILS a. Materials The chemicals used in the present study are, Prpylene glycl and 1-pentanl which are f AR grade btained frm Merck C. Inc., Germany, with purities f greater than 99%. All the chemicals were further purified by standard methds [11] and nly middle fractins were cllected. b. Measurements All binary mixtures were prepared gravimetrically in air-tight bttles and adequate precautins have been taken t minimize evapratin lsses. Befre use, the chemicals were stred ver.4nm mlecular sieves apprximately fr 72 hurs t remve water cntent and then degassed. The mass measurements were perfrmed n a digital electrnic balance (Mettler Tled AB 135, Switzerland) with an uncertainty f ± -8 kg. The binary mixtures were prepared just befre use. The uncertainty in mle fractin was estimated t be less than ±.1. The viscsities were measured with Ostwald viscmeter. The viscmeter was calibrated at each temperature using redistilled water. The uncertainty in viscsity measurement is up t.1mpa-s. The flw time has been measured after the attainment f bath temperature by each mixture. The flw measurements were made with an electrnic stp watch with a precisin f.1s. Fr all the pure cmpnents and 17

3 mixtures, 3 t 4 readings were taken and the average f these values were used in all the calculatins. The densities f the pure cmpunds and their mixtures were determined accurately using ml specific gravity bttles. The average uncertainty in the measured density was ±.1 kg/m 3. The speed f sund was measured with a single-crystal variable path interfermeter (Mittal nterprises, New Delhi, India) perating at a frequency f 2 MHz that had been calibrated with water and benzene. The uncertainty in the speed f sund was fund t be ±.1m/s. where is the density f the mixture and x 1, M 1, and 1 and x 2, M 2, and 2 are the mle fractin, mlar mass, and density f pure cmpnents 1 and 2, respectively. The excess values f free length (L f ), Gibbs free energy (G * ) and enthalpy (H ) were calculated by using the expressins given in literature [15] as fllws, L f = L f K T ( id ) 1/2 (5) Where L f represents the calculated value fr the mixture and K T represent a temperature dependent cnstant whse value is K T=( T)x -8. c. Cmputatinal Details The values f experimentally determined density and speed f sund fr the binary mixtures f Prpylene glycl with 1- Pentanl at 33 K ver the entire cmpsitin range. xcess enthalpy H was calculated frm usual relatin. H H ( x H x H ) (6) In the present wrk the authrs have calculated the excess values f isentrpic cmpressibility and excess free length values t check the applicability f therm dynamical ideality (the ideal mixing rules) t the cmpnents under study. The excess values f isentrpic cmpressibility were calculated as fllws, = id (1) Where represent the calculated value f isentrpic cmpressibility fr the mixture 1 U 2 is its excess value, id is the ideal isentrpic cmpressibility value, is the density and U represents the speed f sund. id fr an ideal mixture was calculated frm the relatin recmmended by Bensn and Kiyhara [12, 13] and Duheret et al [14]. 2 2 id TVi ( αi ) iαi Ks = i K s,i -T xv i i Cp,i xic p,i,i i V α i C p,i in which,,, are the isentrpic cmpressibility, mlar vlume, isbaric thermal expansin cefficient and mlar isbaric heat capacity f pure cmpnent i, T represents abslute temperature, i is the vlume fractin and x i represents the mle fractin f i in the mixture. The density values have been used t calculate the excess vlumes, V, using the fllwing equatin, x M x M x M x M V (2) (3) (4) Where H represents the calculated value f enthalpy fr the mixture and H 1, H 2 represent enthalpy f pure cmpnents 1 and 2, respectively. III. RSULTS AND DISCUSSION The values f density, viscsity and speed f sund fr the binary liquid mixtures f prpylene glycl and pentanl at 33 K temperatures were determined and are given in Table 1. Density : ρ l = ρ wt w wt wt l Viscsity (ŋ): Viscsity (ŋ): η l = η wt t w ρ w ρ l t l Ultra snic velcity (U) = f.λ ms -1 f=frequency f the generatr = 2 x 6 hertz = wavelength = 2d/n Where d = average f taking scillatins. n = n. f scillatins Table 1:Density, ultrasnic velcity and viscsity fr different mle fractins at rm temperature. MleFractin x1 Density (Kg. m -3 ) UltrasnicVelcity U(m.s -1 ) Viscsity η (m.pa.s)

4 Frm these values, varius therm-acustic parameters like a isentrpic cmpressibility (), free length (L f), free vlume (V f), and enthalpy (H) have been determined and excess values like the excess isentrpic cmpressibility ( ), excess mlar vlume (V), excess free length (L f ), and xcess enthalpy (H ), have been calculated. The values f therm-acustical parameters f intermlecular free length (L f), adiabatic cmpressibility (),free vlume (V f), and enthalpy (H) at temperatures T=33 K are given in Table 2 L f Table 2: The values f therm-acustical parameters such as intermlecular free length (L f), adiabatic cmpressibility (),free vlume (V f), internal pressure (π), enthalpy (H)in binary liquid mixtures cntaining prpylene glycl and pentanl at temperatures T = 33 K MleFr actin x1 Isentr pic cmpre ssibilit y() Free length (Lf) Free vlume (V f) nthalpy (H) MOLFRACTION Fig.2. Mle fractin with L f and the values f excess therm-acustical parameters such as excess intermlecular free length (L f ), excess adiabatic cmpressibility ( ), excess free vlume (V f ), excess enthalpy (H ) and at temperatures are given in Table 3. The variatins f the abve excess therm-acustical parameters at temperatures T=33 K with the mle fractins f prpylene glycl are represented in the figures frm Fig-1t Fig-9 MleFr actin x1 xcess Adiabatic cmpressibi lity K S (m 2.N -1 ) xcess Intermlecular free length L f * -13 /m xcess Free vlume V ( m 3.ml - 1 ) xcess nthalpy H (J.ml -1 ) MOLFRACTION Fig.1. Mle fractin with K S 19

5 Table 3 : The values f excess therm acustical parameters such as excess intermlecular free length (L f ), excess adiabatic cmpressibility (K S ), excess free vlume (V f ), ) and excess enthalpy (H ) in a binary liquid mixture cntaining prpylene glycl and pentanl at temperatures T=33 K are given belw in Table 3 and in figures 6-9. V f MOLFRACTION K S * -12 Fig.3. Mle fractin with V f 7.+8 Fig.6. Mle fractin with K S p i MOLFRACTION Fig.4. Mle fractin with p i Frm Fig-6 represents the variatins f excess adiabatic cmpressibility (K S ) in binary liquid mixtures cntaining prpylene glycl and pentanl ver the entire mle fractin range f prpylene glycl at temperature T= 33 K. It is bserved that the excess adiabatic cmpressibility (K S ) values are negative. This indicates that the attractive frces between the mlecules f cmpnents are strnger [16] than the intra-mlecular attractins in each cmpnent. Accrding t Frt and Mre [17] a negative excess cmpressibility is an indicatin f strng heter-mlecular interactin in the liquid mixtures which is attributable t charge transfer, diple-diple, diple-induced diple interactins, and hydrgen bnding between unlike cmpnents. In the present study, the excess cmpressibility is negative and it suggests the existence f strng intermlecular interactins in the binary liquid mixture H L F * MOLFRACTION Fig.5. Mle fractin with H MOLFRACTION Fig. 7. Mle fractin with L f

6 Frm Fig-7, it is bserved that the excess intermlecular freelength values are negative fr the entire mle fractin range. The negative values f excess intermlecular free length suggest that there exist strng interactins between the cmpnents f liquid mixture 16 5 mlecular interactins between the cmpnent mlecules f liquid mixture and als interactins becme weaker with increase f temperature. The variatins f intermlecular free length (L f) with mle fractin at temperatures T=33 K is represented and it is bserved that, the value f intermlecular free length decreases with increase in mle fractin. The decrease in intermlecular free length with mle fractin indicates strng intermlecular interactins between the cmpnent mlecules f the liquid mixture. V F 4 3 The variatins f excess intermlecular free length (L f ) with the mle fractin f prpylene glycl ranging frm t 1 at temperatures T=33 K in the binary liquid mixtures cntaining prpylene glycl and pentanl is at 33 K is as shwn in negative. Therefre the mlecular interactins are bserved and may due t frmatin hydrgen bnd between the cnstituents mlecules. MOLFRACTION Fig.8. Mle fractin with V f The variatins f excess free vlume (V f ) with the mle fractin f prpylene glycl is represented in Fig-8. It is bserved frm Fig-8 values are negative ver the entire cmpsitin range. This suggests that the cmpnent mlecules are mre clse tgether in the liquid mixture than in pure liquids frming the mixture, indicating that strng attractive interactins[18]. The variatin f excess enthalpy in the present binary system is as shwn in Fig-9 it is bserved that H values are negative ver the entire cmpsitin range f prpylene glycl. The negative values f H suggest strng interactins [19]. H MOLFRACTION Fig. 9. Mle fractin with H the variatins f adiabatic cmpressibility( K S) with respect t the mle fractin at temperatures T= 33 K. It is bserved table frm table 2. the value f adiabatic cmpressibility decreases with increase in mle fractin. Accrding t Ali et al, these types f variatins indicate that there exist strng IV. CONCLUSIONS The excess parameters like K S, V f, L f, and H are calculated frm the experimentally determined speed f sund, density and viscsity values. The frmatin f hydrgen bnd between the mixtures is identified by studying the variatins in these parameters thrugh mlecular interactins between the tw mieties. ACKNOWLDGMNTS The authrs acknwledge Suriya Shihab fr help rendered in this wrk. The authrs gratefully acknwledge University Grants Cmmissin Departmental Special Assistance at Level I prgram N. F.53/1/ DSA- 1/15 (SAP-1), dated 12 May 15, and Department f Science and Technlgy- Fund fr Imprving Science and Technlgy prgram N.DST/FIST/ PSI 2/11 dated , New Delhi, t the department f Physics, Acharya Nagarjuna University fr prviding financial assistance. RFRNCS [1] S.L Oswal, P. Oswal, R.P. Shalak. Speed f sund, is ntrpic cmpressibilities and excess mlar vlumes f binary mixtures cntaining p-dixane. J Sl Chem. 27(1998) p.57-. [2] H. Kumar, M.Kaur, R Gaba, K.Kaur. Thermdynamics f binary liquid mixtures f cyclpentane with 2-prpanl, 1- butanl and 2-butanl at different temperatures. J Therm.Anal. Calrim. 5 (11) p [3]. Zrebski,. Waligra. Densities, xcess Mlar Vlumes, and IsbaricThermal xpansibilities fr 1,2- thanedil + 1- Butanl, r 1-Hexanl, r 1-Octanl in the Temperature Range frm ( t ) K. J. Chem.ng. Data. 53 (8) p [4] A. Bruń, M.,.Żurada, A Bald, Densities and excess mlar vlumes fr mixtures f methanl with ther alchls at temperatures ( K) J Therm. Anal. Calrim. () p [5] S.S Sastry, Babu S, T. Vishwam, K Parvateesam, H.S Ting. xcess parameters fr binary mixtures f ethyl benzate with 1-prpanl, 1-butanl and 1-pentanl at T=33, 38, 313, 318, and 323 K. Phys B. 4 (13) p [6] R.F Checni. xcess mlar enthalpy fr methanl, ethanl, 1- prpanl, 1-butanl + n-butylamine mixtures at and K at at mspheric pressure. J Therm. Anal. Calrim.1 ( ) p

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