Chaturvedi, L. K.

Lakhanpal, M. L.

Puri, Tripta

Sharma, S. C.

English

NOPR

indian Journal of ChemistryVol. 14A, September 1976, pp. 645-648Thermochemical Studies on Ternary Systems: Part I-Enthalpies ofMixing of Polyoxyethylene Glycols in Aqueous Dioxane & Ethyl AlcoholM. L. LAKHANPAL, L. K. CHATURVEDl, TRIPTA PURl & S. C. SHARMADepartment of Chemistry, Panjab University, ChandigarhReceived 25 September 1975; accepted 16 January 1976Enthalpies of rnixing (~Hm) of some low molecular weight polyoxyethylene ~lycols with mixedsolvents (dioxane-water and ethanol-water) have been determined at 48.20 usin~ an isothermalphase-change calorimeter. The experimental values have been compared with those calculatedtheoretically [Indian J. Chern., 13 (1975), 129] on the basis of random rntxing of components ina ternary system.IThas been shown- that the enthalpy of mixing(~Hm) of a substance (component 3) with amixed solvent (mixture of components 1 and2) can be expressed in terms of the enthalpies ofmixing of corresponding binary mixtures by therelation[Xl +xs XZ+x3 ( ) AH J~Hm=11>3 -- ~Hla+ ._- ~HZ3- Xl +X2 u 12CPal CPS2... (1)where I1>s is the volume fraction of component (3)in the ternary mixture, Xl' x2 and Xa are the molefractions of components in the ternary system, ~H13'~H2S' ~H12 are the enthalpies of the binary mixtures,CPSl and CP32 are the volume fractions of component(3) in the binary mixtures 3,1 and 3,2. Relation(1) is based on lattice mo.lel which assumes completerandom mixing of components in the binary andternary mixtures. It was found! that even forpolyoxyethylene glycol (mol. wt 200)-dioxane-watersystem, (in which all the components are polar) afairly good agreement was obtained between theexperimental values and those calculated from re-lation (1). For further testing the validity ofrelation (1), enthalpies of mixing for variouspolyoxyethylene glycol-mixed solvent systems havebeen examined experimentally. The data on theenthalpies of mixing have been discussed in thelight of relation (1).Materials and MethodsPolyoxyethylene glycol fractions of molecularweights 200, 600 and 1500 supplied by (UnionCarbide, Canada), were quite pure but were subject-ed to prolonged evacuation at 50° before use. Thesolvents dioxane, ethanol and water were purifiedby the literature methods.The enthalpies of mixing were determined at48·2° employing an isothermal phase-change calori-meter in which cetyl alcohol- was used as thedilatometric fluid.Results and DiscussionThe experimental data 01' enthalpies of mixmgof polyoxyethylene glycol (mol. wt 200) withdioxane-water mixtures of different compositionshave already been reported-. The present data onenthalpies of mixing of the glycols (mol. wts 600and 1500) with different compositions of dioxanewater mixtures and of the glycols (mol. wts 200, 600and 1500) with different compositions of ethanol-water mixtures have been plotted against polymervolume fraction (11)3) in Figs. 1 and 2, respectively.These figures also include the plots of glycol-dioxane/ethanol (0·0% of water) and glycol-watersystems (0% of dioxane/ethanol). It is seen thatsimilar to the behaviour of polyglycol (mol. wt 200)-dioxane system-, the values of ~m (Figs. 1 and 2)decrease regularly with increasing concentrationof water in the mixed solvents. The dependenceof ~m on the amount of water in mixed solventsis such that each plot in these figures appears tobe a composite curve of the two extreme curves(at 0·0% and 100% water in mixed solvent). Thisimplies that ~H •••depends on the relative amountsof the liquids in the mixed solvent. This observationqualitatively supports the basic assumption of com-plete random mixing in the derivation of the Eq.(I).The enthalpies of the various binary mixtures~HlS and ~H23 are given in Figs. 1 and 2 (curvesfor 0·0% water and 100% water) and of ~H12 fordioxane-water and ~Hu for polyglycol (mol. wt200)-water are available in the Iiterature-, The~H12 values for ethanol-water system have beendetermined. It is observed that an S-type plotsimilar to dioxane-water system- is obtained when~H12 for ethanol-water system is plotted againstvolume fraction of water. The values of ~H12 arepositive at low water concentrations and becomenegative at high water concentrations. Comparedwith the dioxane-water system, the magnitudes ofendothermic and exothermic values of ~H12 arerelatively smaller.Comparison between the experimental and theoreticalvalues of ~Hm for ternary systems - The theoreticalcalculations of ~Hm have been made by means ofEq. (1) and compared with experimental valuesas shown in Tables 1 and 2. For solutions of poly-glycols (mol. wt 600 and 1500) in dioxane-watermixtures, the agreement between the theoretical645100-200.!!.E -300-auE-400~-e-500.!!oEe.,-50E:r<II~r'INDIAN J- CHEM., VOL. 14A, SEPTEMBER 1976600 1500lA CONCENTRATIOH0'0 %-0-0-<2·0 IJ -0-<>-5·0 " -A-6-10·0 I' •.•.20'0 ~ ••.••40·0 q .•..••60·0 "' ••••80'0 " ••.•..100'0//-'o o-a 0·61>30·.200100;-------------------------------------~WATER CONCENTRATION0·0 ~-o-o-2 .0 " -<>-<>-5·0 1/ -A-6-10·01/ •.•.20·01/-.......-40·01/ ..•..••60·01/ ••..•.eo-e '/ ..•..•.100·0 1/ ~0·41·0 0 0·2600WATER CONC.O' 0 Ok -o-c>-2'0 II •.•.5 •0 /I -I:r-l:r10'0 " -0-0-20'0 'I -*'300or-t-----~=-----------------~-100WATER CONC.O-O%~2·0/, •.•.•5'0I'~10-0 1/-0-0--150 20'0 'I '*"*-1000'8o oFig. 1 - Plots of~H •••versus <1>. forpolyoxyethyleneglycols (mol. wt600 and 1500)-dioxane-watersystems1500, 1\\JOOWATER CONC.O'Ooh-D-O-2·0" ...•.•5•0 # -lir-lr10'0 'I -<>-<>-zo-ou '**o2001'0 o 0·. 1-0Fig. 2 - Plot of W •••versus </>3 for polyoxyethylene glycols (mol. wt 200. 600 and 1500)-ethanol-water systems646LAKHANP AL et al.: ENTHALPIES OF MIXING IN NON-AQUEOUS SOLVENTSTABLE 1- COMPARISON BETWEEN THE EXPERIMENTAL AND CALCULATED· VALUES OF AHm FOR POLYOXYETHYLENEGLYCOLS-DIOXANE-WATER SYSTEMAHm (caljmole)Water('Yo): 2 5 10 20 40 60 80POLYOXYETHYLENE GLYCOL (MOL. WT 600)0·01 4·0 6·5 10·0 1·0 2·0 4·0 4·0(2·0) (1,0) (2'0) (2'0) (3'0) (4,0) (4'0)0·02 6·5 8·0 14·0 -2·0 -6,0 -10·0 -8,0(4·5) (1,0) (-5·0) (-6,0) (-10'0) (-10'0) (-8·0)0·05 8·0 4·0 2·0 -8,0 -16·0 -28·0 -28'0(9'0) (3·0) (-12'0) (-20'0) (-24'0) (-28'0) (-28'0)0·10 8·5 -18·0 -28'0 -26,0 -48·0 -60·0 -72,0(12·5) (-11'0) (-30·0) (-42'0) (-60·0) (-48'0) (-72'0)0·20 2·0 -51·0 -64·0 -65·0 -114 -144 -188(13'5) (-32'0) (-67'0) (-90·0) (-126) (-144) (-176)0·30 -10·0 -72·0 -101 -108 -180 -232 -300(11-5) (-52·0) (-105 (-148) (-192) (-224) (-268)0·40 -24'0 -89·0 -142 -152 -234 -320 -412(8,0) (-68·5) (-135) (-200) (-246) (-300) (-352)0·50 -35-0 -12-0 -190 -200 -282 -416 -500(-3-0) (-80-0) (-163) (-234) (-312) (-378) (-432)0-60 -66-0 -144 -226 -238 -320 -508 -584(-3-5) (-85-0) (-175) (-260) (-356) (-448) (-512)0·70 -86-0 -149 -244 -274 -354 -556 -656(-7·0) (-73-0) (-174) (-266) (-384) (-488) (-580)0·80 -93·0 -137 -221 -290 -356 -524 -604(-4-0) (-49-0) (-157) (-242) (-364) (-484) (-588)0·90 -89-0 -95·0 -139 -256 -276 -408 -480(-1-5) (-7-0) (-44·0) (-140) (-264) (-372) (-480)0·95 -50·0 -45-0 -73-0 -170 -146 -272 -240(-0-5) (-6-5) (-23-0) (-26-0) (-146) (-232) (-240)POLYOXYETHYLENE GLYCOL (MOL_WT 1500)0·01 1-0 6-0 26·0 -3-0 -2·0 -12-0 -8'0(16'0) (36-0) (7-0) (1-0) (-6-0) (-6-0) (-4-0)0·02 3-0 2-0 20-0 -6-0 -4-0 -20'0 -14-0(17-0) (22-0) (5,0) (-2-0) (-9,0) (-8'0) (-12-0)0·05 11-0 -12-0 -3-0 -18-0 -18-0 -40·0 -40·0(11-0) (-3'0) (-10-0) (-18-0) (-28-0) (-28-0) (-36-0)0-10 17-0 -32-0 -36·0 -42-0 -43-0 -72-0 -84-0(7-0) (-20-0) (-36-0) (-50'0) (-56-0) (-68-0) (-76-0)0-20 10-0 -60·0 -800 -90-0 -112 -160 -188(10·0) (-36'0) (-74-0) (-114) (-150) (-160) (-172)0·30 -4·0 -84-0 -116 -134 -176 -240 -292(7-0) (-54-0) (-110) (-164) (-222) (-258) (-280)0·40 -21-0 -110 -153 -176 -260 -234 -392(5'0) (-74-0) (-142) (-209) (-292) (-352) (-376)0-50 -60-0 -142 -196 -220 -320 -400 -488(-7·0) (-94-0) (-168) (-246) (-348) (-428) (-476)0-60 -101 -166 -236 -264 -368 -458 -572(-25-0) (-108) (-194) (-274) (-388) (-480) (-552)0-70 -123 -186 -274 -310 -412 -498 -648(-52-0) (-144) (-220) (-290) (-398) (-514) (-616)0-80 -142 -202 -294 -352 -424 -496 -688(-90-0) (-174) (-248) (-294) (-380) (-510) (-616)0·90 -160 -206 -298 -328 -408 -448 -636(-134) (-212) (-270) (-290) (-346) (-452) (-540)0·95 -157 -144 -280 -290 -376 -320 -500(-170) (-230) (-270) (-286) (-305) (-320) (-400)*Calculated values of t;Hm are given in parentheses.and experimental values is not so good at very lowwater concentrations and at very high polymerconcentrations, unlike the solutions of polyglycol(mol. wt 200)_ Agreement is satisfactory at othercompositions. The deviations from theory at extremeconcentrations may be attributed to (i) larger sizeof polyglycol molecules, (ii) non-availability of watermolecules (at low water and high polymer concen-trations) and (iii) the polar nature of the componentsinvolved. All these factors tend to inhibit completerandom mixing such that Eq. (1) cannot be strictlyapplicable.For solutions of polyglycols (mol. wt 200) inethanol-water mixtures, the agreement between thetheoretical and experimental values of AHm (Table 2)is fairly good but the agreement is not so good for647INDIAN J. CHEM., VOL. 14A, SEPTEMBER 1976TABLE 2-COMPARISON BETWEEN THE EXPERIMENTALAND CALCULATED-VALUES OF 1:Ji". FOR POLYOXYETHYLENBGLYCOL-ETHANOL-WATERSYSTEM1:Ji". (caljmole)Water('Yo): 2 5 10 20POLYOXYETHYLENEGLYCOL(MOL.WT 200)0·01 53-5 (55·5) 37'0 (58'5) 47·0 (42·5) 33·0 (20,0)0·02 54·0 (57,0) 37·5 (59'5) 47·5 (46'0) 36·0 (29'0)0·05 30·0 (42·5) 34·0 (58'5) 42·5 (48·5) 37·0 (29'0)0·10 12·0 (27·5) -21,0 (4-5) -27·5 (-7-5) 15·0 (-3-0)0·20 15·8 (18'0) -16·5 (-0·5) -46,0 (-23'0) -45·0 (-57'0)0·30 28·0 (28,0) -7·5 (4·5) -52-6 (-35-0) -75·0 (-84-0)0·40 39·5 (37'3) 4·0 (2-5) - 56·0 (- 54'0) -115 (-121)0'50 45·8 (41,3) 18·0 (-3·0) -56·0 (- 54-0) -155 (-121)0·60 48·5 (42,4) 21·5 (4·5) -54,0 (-62'5) -158 (-131)0·70 48·0 (41'0) 20·0 (6·5) -49·0 (-64'5) -150 (-133)0'80 44·0 (31,3) 15·0 (-2-5) -40·0 (-52-5) -125 (-120)0·90 32·5 (15-0) 8·0 (-5'0) -24·0 (-24'0) -77·0 (-63'0)0·95 20'0 (7'0) 4·5 (-3·0) -12·5 (-7·5) -42·0 (29'0)POLYOXYETHYLENEGLYCOL(MOL.WT 600)0·01 50·0 (31·3) 10·0 (40,0) 10'0 (1·5) 19·0 (22·0)0·02 56·3 (47·5) 35·0 (41-0) 30'0 (3'0) 15·0 (19'0)0·05 73·3 (25,0) 35·0 (19,0) 44'0 (8'0) -2'0 (-2'0)0·10 25·0 (41·3) 2·0 (30'0) 30'0 (13-0) - 32-0 (- 9'0)0·20 72·5 (81'3) 17·0 (56'0) -4·0 (22·0) -89,0 (-22·0)0·30 114 (119) 40·0 (82'0) 5·0 (32'0) -118 (-35'0)0'40 150 (154) 67·0 (110) 17-0 (UO) -1340 (-47'0)0·50 190 (189) 99·0 (132) 31·0 (54-0) -1340 (-54'0)0·60 220 (211) 136 (160) 46·5 (67'0) -122 (-49'0)0·70 245 (233) 173 (188) 67·0 (82'0) -101 (-38'0)0·80 263 (248) 185 (209) 88·0 (120) -67·0 (-12'0)0·90 218 (200) 178 (208) 109 (1340) -30,0 (50'0)0·95 113 (113) 160 (193) 109 (123) -14·0 (79'0)POLYOXYETHYLENEGLYCOL(MOL.WT 500)0'01 6·3 (42,5) 30·0 (30'0) 5·0 (22'0) -5,0 (12'5)0·02 25-0 (45-0) 40·0 (38'0) 10'0 (27'0) -7·5 (15-0)0·05 52·5 (40'0) 48'0 (36'0) 30'0 (23-0) -20·0 (5-0)0·10 57·5 (41·3) 30·0 (25-0) 39'0 (3'0) -42·0 (-23'0)0·20 29·3 (41'0) 20·0 (27'0) 27·0 (-4·0) -74·5 (-49'5)0'30 70·0 (95·0) 55·0 (63·0) -1·5 (17'0) -92·5 (-56'0)0·40 113 (141) 94·0 (100) -14·0 (39'0) -115 (-53·0)0·50 188 (187) 133 (140) 27·0 (63'0) -117 (-41·0)0·60 290 (225) 180 (169) 70·0 (86'5) -108 (34-0)0·70 298 (230) 217 (177) 106 (89'0) -94·0 (-37'0))0·80 300 (220) 234 (147) 1340 (69·0) -75·0 (-40·8)0·90 278 (163) 225 (90'0) 128 (27'0) -51·5 (-39'5)0·95 182 (88·0) 170 (25,0) 85·0 (8,0) - 35·0 (-25·0*Calculated values of 1:Ji". are given in parentheses.solutions of polyglycols (mol. wts 600 and 1500).It may be seen that in these ternary systems,maximum amount of water in ethanol-water mixtureis 20%. As observed for polyglycol-dioxane-watersystems, a comparison in the case of solutions ofpolyglycols in ethanol-water mixtures shows thatcomplete random mixing is not possible, especially.when the amount of water is relatively small and/orpolymer molecular weight is high. It may berealized that the situation is made even morecomplex since ethanol in these ternary systems isalso capable of forming hydrogen bonds betweenits molecules besides water.AcknowledgementOne of us (L.K.C.) is grateful to Shri N.S.Venkatesan, Director, TBRL, Sector 30, Chandi-garh, for the grant of study leave and encourage-ment.References1. LAKHANPAL,M. L., CHATURVEDI,L. K. & SHARMA,S. C.,Indian]. Chem., 13 (1975), 129.2. LAKHANPAL,M. L. & PARASHAR,R. N., Indian J. cu«,S (1970), 368.648

Thermochemical Studies on Ternary Systems: Part I-Enthalpies of Mixing of Polyoxyethylene Glycols in Aqueous Dioxane & Ethyl Alcohol

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Thermochemical Studies on Ternary Systems: Part I-Enthalpies of Mixing of Polyoxyethylene Glycols in Aqueous Dioxane & Ethyl Alcohol

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