VAPOR PRESSURE, DENSITY, VISCOSITY AND REFRACTIVE INDEX OF DIMETHYL SULFOXIDE + 1,4-DIMETHYLBENZENE SYSTEM

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1 HUNGARIAN JOURNAL OF INDUSTRIAL CHEMISTRY VESZPRÉM Vol. 3. pp. 3-9 (3) VAPOR PRESSURE, DENSITY, VISCOSITY AND REFRACTIVE INDEX OF DIMETHYL SULFOXIDE +,4-DIMETHYLBENZENE SYSTEM O. CIOCIRLAN, O. IULIAN Departent of Appled Physcal Chestry and Electrochestry, Faculty of Industral Chestry, Poltehnca Unversty of Bucharest, 33 Splaul Independente, 4, Roana Ths work reports the experental results of the sotheral vapor-lqud equlbru data between 33.5 K and K, denstes, vscostes and refractve ndces fro 98.5 to 33.5 K of the dethyl sulfoxde +,4-dethylbenzene syste over the entre range of xture coposton. The obtaned PTX data were correlated and estated by the Wlson, NRTL and odels. The excess Gbbs energy and actvty coeffcents were calculated and copared wth the others excess propertes. Excess olar volues, vscosty devatons and devatons n refractvty were calculated fro experental data; all the coputed quanttes were ftted to the Redlch-Kster equaton. The resultng excess functons were nterpreted n ters of the nteractons between the olecules n the bnary syste. Keywords: VLE data, xture propertes, correlatve and predctve ethods, olecular nteractons Introducton Contnung our work on the therodynac of the nonelectrolte systes, the present paper s a part of a study of the bnary systes contanng dethyl sulfoxde (DMSO) and aroatc hydrocarbons, nterestng as xed solvents []. Dethyl sulfoxde s a versatle nonaqueous, aprotc, hghly polar self-assocated solvent (havng a dpole oent µ =3.9 D at 98.5 K) used extensvely n knetc studes, electrochestry and as a solvent for polyers. Bnary xtures of DMSO wth aroatc solvents are nterestng n studes of polyer scblty, polyer phase dagras, and preferental nteractons n xed solvents []. Ths work reports sotheral experental vapor lqud equlbru (VLE) data at teperatures n the range fro 33.5 K to K and experental data of densty, vscosty and refractve ndex n the teperature range fro 98.5 to 33.5 K for the dethyl sulfoxde +,4-dethylbenzene syste. The VLE data were correlated by eans of Wlson [3] and NRTL [4] odels; ths work has also served to test the predctve capacty of the group contrbuton ethods: orgnal [5] and [,7]. Excess olar volues, vscosty devatons and devatons n refractvty were calculated fro experental data; all the coputed quanttes were ftted to the Redlch-Kster equaton. After our knowledge, VLE data for ths bnary syste are not nuerous [8]; there s only one source n the lterature [9]. No lterature data on denstes, vscostes and refractve ndces are avalable for ths syste, except on denstes at 33.5 K []. Experental Materals The used substances were purfed by dstllaton. Dethyl sulfoxde was dstlled under vacuu at.8-.9 kpa and K. The analytcal-reagentgrade,4-dethylbenzene fro Fluka (p.a.) was used wthout further purfcaton. The purty was checked by refractve ndex, densty and gas chroatography. It was better than 99.5 ass per

2 4 cent. The experental values of densty, refractve ndex and vscosty of the pure coponents are presented n Table and copared wth lterature values. Table. Experental and lterature values for densty (ρ), refractve ndex (n D ) and vscosty (η) of the pure coponents ρ, kg -3 n D η, Pa s T, K lt. exptl lt. exptl lt. exptl dethyl sulfoxde , , ,4-dethylbenzene , , ,.493 Vapor pressure The total vapor pressure of the bnary xture was easured at teperatures between 33.5 K and K by a statc ethod, wth a glass sotenscope of the Sth and Menzes type, wth soe odfcatons [], whch allows the easureents of VLE at subatospherc pressures at teperatures up to 43.5 K. Vapor pressures are easured by eans of a Hg anoeter and a cathetoeter, readngs accurate to wthn. kpa. The teperature was controlled by a U- type therostat and easured wth an Hg theroeter wth an estate accuracy of.5 K. The substances were degassed pror to the easureents by freezng-thawng processes under vacuu. The vapor phase volue of the apparatus beng relatvely sall, calculaton showed that the error n coposton due to vaporzaton s wthn ths lt. Densty, Vscosty and Refractve Index Denstes, ρ, of the pure solvents and the xtures were easured wth an Anton Paar DMA 45 denseter wth a precson of ±.5 g c -3, between 98.5 and 33.5 K. The DMA cell was calbrated wth ultra pure water at atospherc pressure. The saple sze was.7 c 3, and the saple therostat was controlled to ±. K. Kneatc vscostes, ν, of the pure coponents and ther xtures were deterned at 98.5, 33.5, 33.5 and 33.5 K usng an Ubbelohde capllary vscoseter for whch the uncertanty of the flow te easureent was ±. s; the correspondng uncertanty n the kneatc vscosty was ±. - s -. At least four tes flow easureents were perfored for each coposton and teperature, and the results were averaged. The vscoseter was calbrated usng double dstlled water; t was placed n a therostat antaned constant wthn ±.5 K. Refractve ndces values for the D-lne, n D, were easured wth a therostated Abbe refractoeter wth a precson of ±.. All easureents were done n a therostat antaned at ±.5 K. The bnary xtures were prepared by ass; the precson of the ole fracton s estated to be better than ±.. Results and Dscusson The easureents of the total pressure were carred out at varous copostons on the large teperature range. For each bnary xture the dependences between experental pressure and teperature were establshed. The functons P = f(t) obtaned by polynoal regresson were used to calculate the VLE data at 33.5 K, 33.5 K, 33.5 K and K. The soothed data resulted fro experental easureents are reported n Table. Table Vapor-lqud equlbru data for the bnary dethyl sulfoxde () +,4-dethylbenzene () syste fro 33.5 to K. Soothed values of the pressure by polynoal regresson T, K P, kpa X The teperature dependence of the pure coponent vapor pressures, P o, was calculated usng the Antone equaton: o B ln P ( kpa) = A () T( K) C where the Antone constants A, B and C are reported n Table 3.

3 5 Table 3 Result of correlaton and predcton wth Wlson, NRTL and odels for dethyl sulfoxde () +,4- dethylbenzene () syste Copound A B C dethyl sulfoxde ,4-dethylbenzene The varous odels are used for correlaton and predcton of bnary VLE data: the equatons based on local coposton concept (Wlson and NRTL) and the group contrbuton ethods. The results of correlaton wth Wlson and NRTL odels are presented n Table 4, whch ncludes the odel paraeters values and the statstcal paraeters: average percentage devaton n pressure, P, and standard devaton, σ. Predcton of VLE for the bnary syste at 33.5, 33.5, 33.5 and K has been carred out by the orgnal ethod and ts odfcaton,. The group nteracton paraeters were those publshed by Red [5], Hansen [] and Gehlng [,7]. The results of predcton are also presented n Table 4. The Wlson and NRTL gve a slar and good representaton of experental data (except at 33.5 K teperature); σ and P characterse the data as satsfactory. It can be observed that the descrpton of ths syste by the orgnal ethod shows good agreeent wth the experental data, lke Wlson and NRTL odels; the odfed gves less satsfactory results, especally at hgh teperature. The experental and calculated (wth Wlson odel) total pressures vs. lqud and vapor copostons for 33.5 K, 33.5 K, 33.5 K and K are presented n Fgure. In the sae phase dagra the curves represent calculated data and the ponts, experental data. The actvty coeffcents were calculated wth Wlson equaton for bnary systes. Fgure presents the dependence of the actvty coeffcents of the coposton at 33.5 K, the ltng values at nfnte dluton of these coeffcents beng gven. We have also coputed and represented the varaton of the excess Gbbs energy of the syste, whch shows postve devatons fro the deal. The coparson of axu obtaned value of G E wth lterature, at 33.5 K, s satsfactory [9]. Table 4 Experental values of densty, kneatc vscosty and refractve ndex of dethyl sulfoxde () +,4- dethylbenzene () syste fro 98.5 to 33.5 K Model Paraeters, Statstcal paraeters J ol - σ a, Hg P b, % 33.5 K λ Wlson =443.8± 77 λ =4.5±4 NRTL g =47.7±3 (α=.3) g =44.± 89 Orgnal 33.5 K λ Wlson =374.3±7 λ = 34.4±3 NRTL g =4444.±39 (α=.3) g = 99.4± Orgnal 33.5 K λ Wlson =.8±43 λ =3.9±84 NRTL g =.±435 (α=.3) g =345.±535 Orgnal K Wlson λ =977.9±78 λ = 455.±7 NRTL g =49.8±343 (α=.3) g =5777.3±3 Orgnal a Standard devaton σ ={Σ N (P calc ()- P exp ()) /(N-M)}.5 (N: nuber of data ponts and M: nuber of estated paraeters). b Average percentage devaton n pressure P=(/N) Σ N P calc ()- P exp () / P exp () P, kpa X, Y Fg. Experental vapor pressures of dethyl sulfoxde () +,4-dethylbenzene () syste at 33.5 K ( ); 33.5 K ( ); 33.5 K (o); K ( ); correlaton wth Wlson odel ( )

4 , X 8 4 G E, J ol - Fg. Actvty coeffcents and excess Gbbs energy for the dethyl sulfoxde () +,4-dethylbenzene () syste calculated wth Wlson odel at 33.5 K Denstes, vscostes and refractve ndces were easured n the teperature range fro 98.5 to 33.5 K and the easured values were lsted n Table 5. The values of excess olar volue, V E, vscosty devaton, ν, and devaton n olar refractvty, R, were calculated fro the experental data accordng to the followng equatons: E V = V V X () = = ν = ν ν X (3) = R = R R ϕ (4) where X and φ represent the ole fracton and volue fracton, respectvely; V, ν, R, the propertes of xtures, V, ν, R, the propertes of the pure coponents. The values of R were calculated fro the Lorentz-Lorenz equaton [7]. The experental values of V E, ν, and R have been ftted to the Redlch-Kster [8] type polynoals: Y = X n X A k X k = ( ) k (5) where Y represent the excess olar volue, vscosty devaton and devaton n olar refractvty, and A k represents the paraeters. A nonlnear least-squares ethod was used to estate the adjustable paraeters A k. The values of A k and standard devaton σ are gven n Table. Table 5 Paraeters of Eq. 5 and standard devatons of excess functons of dethyl sulfoxde () +,4-dethylbenzene () syste X -3 ρ, ν, kg -3 s -3 ρ, ν, - n D X kg -3 - s n D 98.5 K K K K Table Functon A A A A 3 σ a 98.5 K V E, 3 ol ν, s R, 3 ol K V E, 3 ol ν, s R, 3 ol K V E, 3 ol ν, s R, 3 ol K V E, 3 ol ν, s R, - 3 ol a Standard devaton σ ={Σ N (Y calc ()- Y exp ()) /(N-M)}.5 (N: nuber of data ponts and M: nuber of estated paraeters). The dependence of excess olar volue V E on the ole fracton of DMSO s presented n Fgure 3. The negatve values of V E suggest the presence of specfc nteractons between the xng coponents. V E shows neglgble teperature dependence. Plots of excess vscosty versus the ole fracton of DMSO are shown n Fgure 4. The ν are negatve over the whole coposton range; a

5 rse of teperature akes an ncrease of ν. The vscosty of a xture depends on the olecular nteractons between coponents: generally, xtures wth strong nteractons between dfferent olecules show postve vscosty devatons, whle for xtures wthout specfc strong nteractons, vscosty devatons are negatve. In our xtures the breakng of dpole-dpole nteractons of DMSO contrbutes to the reducton of the vscosty durng the xng process. On the other hand, self-assocaton of DMSO and π electron nteractons n DMSO +,4-dethylbenzene syste [9] ncrease the vscosty, but the effect s not as portant as the breakng of selfnteractons. Consequently, the excess vscosty of all our xtures s oderately negatve; slarly, V E values rean negatve. The presence of ntraolecular nteracton s reflected n postve devatons fro Raoult s law, therefore, postve values for G E. The excess olar refractvty s shown n Fgure 5. The R values are negatve for the whole coposton range for all xtures. The values are ndependent of teperature, as predcted by the theory, the olar refractvty dependng only on the wavelength of lght used for easureent. V E, 3 ol X Fg. 3 Excess olar volues for dethyl sulfoxde () +,4- dethylbenzene () syste at 98.5 ( ); 33.5 K ( ); 33.5 K ( ); 33.5 K (o); correlaton wth Redlch-Kster equaton ( ), s X Fg. 4 Vscosty devatons for dethyl sulfoxde () +,4- dethylbenzene () syste for the teperatures gven n Fgure 3; correlaton wth Redlch-Kster equaton ( ) R, 3 ol X Fg. 5 Devatons n olar refractvty for dethyl sulfoxde () +,4-dethylbenzene () syste for the teperatures gven n Fgure 3; correlaton wth Redlch-Kster equaton ( ) Conclusons The experental data concernng the sotheral vapor-lqud equlbra n the bnary,4- dethylbenzene + DMSO syste have been presented. Eght varous xtures contanng,4- dethylbenzene + DMSO have been analyzed. A good agreeent between experental and calculated values of the pressure has been observed for Wlson and NRTL correlatve ethods and for orgnal - predctve ethod. Experental denstes, kneatc vscostes and refractve ndces data for the bnary syste DMSO +,4-dethylbenzene have been easured at atospherc pressure between 98.5 K and 33.5 K. Excess functons have been calculated and ftted to the Redlch-Kster equaton. The behavour of ths xture has been dscussed n ters of nter and ntraolecular nteractons.

6 8 SYMBOLS A, B, C Antone s equaton paraeters Redlch-Kster s paraeters A k G E g j excess Gbbs energy paraeters of NRTL equaton M nuber of odel paraeters N nuber of experental ponts n D refractve ndex P average percentage devaton n pressure P exp experental total pressure P calc coputed total pressure o P vapor pressure of -th pure coponent R devaton n olar refractvty R olar refractvty of xture R olar refractvty of the -th pure coponent T absolute teperature V E excess olar volue V olar volue of xture olar volue of the -th pure coponent V X γ k λ j lqud-phase ole fractons actvty coeffcents paraeters of Wlson equaton µ dpole oent η, ν dynac and cneatc vscosty, respectvely ν vscosty devaton ν kneatc vscosty of xture ν kneatc vscosty of the -th pure coponent ρ densty σ standard devaton φ volue fracton REFERENCES. CIOCIRLAN O., IULIAN O. and CATRINCIUC M.: 3 th Roanan Internatonal Conference on Chestry and Checal Engneerng, Bucharest, Sept. 3, (n press). AMINABHABI T. M. and MUNK P.: Macroolecules, 979,, 7 3. WILSON G. M.: J. A. Che. Soc., 94, 8, RENON H. and PRAUSNITZ J. M.: AIChE J, 98,, FREDENSLUND A. A, GMEHLING J. and RASMUSSEN P.: Vapor Lqud Equlbra usng, Elsever, Asterda, 977. WEIDLICH U. and GMEHLING J.: Ind. Eng. Che. Res., 987,, GMEHLING J., LI J. and SCHILLER M.: Ind. Eng. Che. Res., 993, 3, WICHTERLE I., LINEK J. and KEHIAIAN H.: Vapor Lqud Equlbru Bblographc Database, Montreul, pp.-9, KARVO M., NISSEMA A. and KAIVAMO T.: Fnn. Che. Lett, 983, 7-8, ABSOOD A. H., TUNUNJI M. S., HSU K. Z. and CLEVER L.: J. Che. Eng. Data, 97,, ARALAGUPPI M. I., AMINABHAVI T. M., HAROGOPPAD S. B. and BALUNDGI R. H.: Aer. Che. Soc., 99, 37, RIDDICK J. A., BUNGER W. B. and SAKANO T. K.: Technques of chestry. Vol. II, Organc solvents, 4 th ed. Wley & Sons, KOROSI G. and KOVATS E.: J. Che. Eng. Data, 98,, TSIERKEZOS N. G., KELARAKIS A. E. and PALAIOLOGOU M. A.: J. Che. Eng. Data,, 45, NIKAM P. S., JADVAV M. C. and HASAN M.: J. Che. Eng. Data, 99, 4, 8-3. PRUETT D. J. and FELKER L. K.: J. Che. Eng. Data, 985, 3, WEAST R. C. and ASTLE M. J.: Handbook of Chestry and Physcs, 3 rd ed., CRC Press Inc., Florda, SUA, LIDE D. R. and FREDERIKSE H. P. R.: Handbook of Chestry and Physcs, 77 th ed., CRC Press Inc., Florda, SUA, DIAZ C., DOMINIGUEZ A. and TOJO J.: J. Che. Eng. Data,, 47, TRC Therodynac Tables; Therodynac Research Center, Texas A & M Unversty: College Staton, TX, 99, n DIAZ C., DOMINIGUEZ A., TOJO J.: J. Che. Eng. Data,, 47, LORES M. T., J. DE LA TORRE, BURGUET M. C. and MONTON J. B.: J. Che. Eng. Data, 999, 44, 89-87

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