Kalidas, C.

Rao, V. Srinivas

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..QxCl -• • • ••· · 8r-· . ·· IM~.N"·~th~N+· • • Cs+· • !=lb+• K+Pr4N+· •No· +Bu. NLi+• P~n4N+Hu4N+·• . H"P4 N+5248444032Or:' 26'<-ece16128420 25 30 35 40T.,mpq:rQlur •• ,45~C50Fi3· 1 - Plots of At·"o and Ao"tj° versus temperature inpropylene carbonatefrom the conductance data. So the 1\.0"'1)° values ofthe R4N+ and ts-, Na+, K+, Rb+, CST,CI-, Br- and 1-,at different temperatures, were obtained from thelimiting ionic conductivity values given in Table 1.The values of viscosity, rt, of the solvent were 2·480(ref. 3), 2'248, 2·050, 1·871 and 1·705 centipoise(± 0·2%) at 25°, 30°, 35°, 40° and 45° respectivelyand were obtained, except that at 25°, in th-elaboratory. The plots of 'fl,0Ao and I\.ij"'l)0 against tem-peratures are given in Fig. 1 from which it may benoted that the Walden product for different ions isalmost independent of temperature. This indicates thatthese ions neither break nor promote the structure ofthe solvent within the temperature range studied pre-sently, apparently because no hydrogen bond structureis present originally in the pure solvent". It appearsthat the temperature dependence of the 'Waldenproduct is not verv useful in the studv of ion-solventinteraction in non-hydrogen bonded ~olvents.A better insight about the ion-solvent interactioncan be obtained if the relative positions of the Ao"'l)°:Ters,:s temperature curves for different ions, givenIn FIg. 1, are compared. It may be noted that forR4N+ ions. the Walden product is larger, the smaller1he size of the ion. This indicates that theelectrostatic ion-solvent interaction, if at all, is veryNOTESweak in these cases so that the smaller the ion, thefaster its movement and the larger the Waldenproduct. The same appears to be true for Cl-, Br-and 1- ions as well. However, reverse is the case withthe common cations which are comparatively muchsmall as compared to the R4N+ ions. In these cases,Walden product decreases with the decrease in thecrystal radius of the cation. This clearly indicatesthe role of electrostatic charge density on the ion ininducing strong ion-solvent interaction and solvation.The smaller the ion, the greater the electrostaticcharge density on the ion, and stronger the ion-solvent dipole interaction, resulting in a larger size ofthe solvadynamic unit so that the size of the solvatedcommon cations in propylene carbonate solution isin the order: Li+>Na+>K+> Rb+>Cs+, in spite of theradii of these ions being in the reverse order. Thesecommon cations exhibit a similar behaviour inN-methylacetamide and N-methylformamide.It thus appears that during migration thecommon cations which are fairly small are coveredwith a sheath of the solvent molecules. HoweverR4N+ and halide ions move more or less as singleand bare ions in propylene carbonate. Further, thesolvation of ions is not appreciably affected bytemperature within the range studied here.Authors are grateful to the Society of the SigmaXi of USA for the financial assistance and alsoto Lucknow University for providing facilities.References1. ]HA, J. S., SINGH, S. & GOPAL, R., Bull. chem . Soc. Japan,48 (1975), 2782.2. PAYNE, R. & THEODOROU, I. E., J. phys. cs-«; 76 (1972),28921.3. MUKHER)I, L. M. & BODEN, D. P., J. phys. Chem., 73(1969). 3965.4. MUKHER)I, L. M., BODEN, D. P. & LINDAUR, R., J. phys.Chem., 74 (1970), 1942.5. JANSEN, M. L. & YEAGER, H. L., J. phys, cse«, 77 (1973),3089.6. SINGH, R. D., RASTOGI, P. P. & GOPAL, R., Can. J. Chem.,46 (1968), 3525.7. GOPAL, R. & JRA, ]. S., J. phy«. Chem., 78 (1974), 2405.Conductance of Hydrogen Halides inDiethylene Glycol at Different TemperaturesC. KALIDAS* & V. SRINIVAS RAODepartment of ChemistryIndian Institute of Technology, MadrasReceived 3 Manh 1975; accepted 18 July 1975Conductance data on hydrogen chloride and hydrogenbromide in diethylene ~lycol in the temperature range25-45°C are reported. Further, the temperature co-efficient of conductance and the Walden product in thistemperature range are presented and it was shown bythe application of 1965Fuosa-Onsager three-parameterequation, that no stgntficant association of the halidesoccurs in this solvent.CONDUCTANCE studies on hydrogen halidesin non-aqueous solvents, especially the amphi-protic solvents, have received considerable attention-.=To whom correspondence should be addressed.129INDIAN J. CHEM., VOL. 14A, FEBRUARY 1976But relatively few data have been analysed2,3 interms of the recent Fuoss-Onsager conductanceequation for possible existence of ion associationof the halides in these media and practically no suchanalysis has been reported, so far, in glycols. Thepresent work, which is in continuation of ourearlier conductance studies on hydrogen chloridein ethylene and propylene glycols', therefore, dealswith the conductance behaviour of hydrogen chlorideand hydrogen bromide in diethylene glycol in thetemperature range 25-45° to elicit information onion association and to understand the nature ofsolute-solvent interactions involving the halides inthis solvent.The purification of diethylene glycol=", detailsof the experimental set-ups, the method of prepara-tion, purification and standardization. of hydrogenchlorides have been described earlier. Hydrogen bro-mide gas, generated by the action of bromine on tetra-line, was passed successively through traps containingtetraline and cone, HlISO. to absorb any traces ofbromine and water respectively before being bubbledinto the solvent. The standardization of the stockhydrogen bromide solution was done similar to thatof Hel. The temperature was generally maintainedto within ± 0·010 by immersing the cell in an oil bathmaintained at the desired temperature for sufficientlylong time for the attainment of thermal equilibrium.13· "-011·0 ',011·0 . 6-045 C -•••-; 10·0N15'0 Euv 004-0 !] 9·0< <8·0 13·0'·0 12·06·0 11·05·0 OOO0 14'0Fig. 1 - Conductance plots for HCl and HBr in diethyleneglycol at different temperaturesThe conductance results of the two acids atdifferent temperatures are presented in Fig. 1 in theform of A versus VL plots. The plots are seen tobe approximately linear in the concentration rangesstudied. Since these concentrations lie outside therange of applicability of the limiting Onsager equa-tion, the data (Fig. 1) were analysed by the Fuoss-Onsager three-parameter equations given byA = Ao-SClJ2yli2 +2EC Y log ('tYl/2)+LCY-AC Y exp(-2'tYl/2)A ... (1)where the various terms have their usual significance.The calculations were performed on an IBM 370computer and revealed no significant associationof either of the halides in the temperature rangestudied. The data were, hence, analysed by Fuoss-Onsager two-parameter equation given byA = AO-SCI/2+2EC log ('t)+LC ... (2)where the various terms have been explained- else-where. The same computer program as above wasemployed for this purpose and had provision forperforming the calculations using Eq. (2) when theassociation constan.t, KA, is less than 10 as obtainedfrom the three-parameter equation. The Ao, theion size parameter, a, and the standard deviation,GA, for the two halides obtained in this manner aregiven in Table 1. The temperature coefficient ofconductance given by 1~~x~; in the temperatureranges 25-35°e and 35-45°e and the Walden productsat the three temperatures are recorded in Table 2.A further indication of the complete dissociationof these halides in this solvent was obtained"by plotting the function, A' (given by Eq. 3)A' = A-Ao+SCl/2-EC log C •.. (3)against the concentration of the acid for the twohalides at the various temperatures and they werefound to be linear with no significant curvature. Itis seen (Tables 1 and 2) that Ao of both the acidsincreases with temperature but the temperaturecoefficients tend to decrease with increase ofTABLE 2 - TEMPERATURE COEFFICIENT AND 'VALDENPRODUCT OF HYDROGEN HALIDES IN DIETHYLENEGLYCOLAcidHClHBrTemp. coeff. Ao1)o (mhO ern! poise) at----------(25-35°) (35-45°) 25° 35° 45°4-190 4·006 2·93 2·77 2·725·035 1·711 2'99 2·99 2·54T.~BLE 1 - LIMITING EQUIVALENT CONDUCTANCE AND ION SIZE PARAMETER FOR THE HYDROGEN HALIDES INDIETHYLENE GLYCOL AT DIFFERENT TEMPERATURESTemp.°CHydroge 1 chlori-te Hydrogen bromi '.eA. a (A) <1A Ao a (A) <1A(mho ern') (mho ems) (mho em') (mho ems)9·76 2·.1±0·1 0·06 9·95 2·11±0·06 0·0613·85 2·.3 ±0·1 0·06 104·96 2·11 ±0·06 0·0619·40 2·39±0·1 0·06 17·52 2·13 ±0·07 0·06253545130temperature. The positive temperature coefficientfor both the acids can be explained'? on the basisthat increase of temperature (a) causes the ruptureof hydrogen bonds in the diethylene glycol moleculesand (b) will facilitate the rotation of solventmolecules by increasing the force causing therotation. Thus both the effects increase themobility of the protons. The ion size parameterobtained for hydrogen chloride is of the same orderas in the case of DMSO-water mixtures-' andis unaffected by temperature changes. The nearconstancy of the Walden product (Table 2) is mostpresumably due to the compensating contributionof the positive temperature coefficient of conductanceof the acids by the negative temperature coefficientof the viscosity of the solvent. The slight decreaseof this quantity with increase in temperature is inagreement- with the observations on hydrogenchloride in propanol-water mixtures.Our sincere thank" are clue to Prof. M. Goffredi ofthe University of Palermo, Italy, for providing us thecomputer programme which made this work possible.We thank the CSIR, New Delhi, for the award ofa senior research fellowship to one of us (V.S.R.).References1. JANZ, G. J. & DANYLUK, S. S., Chem . Rev., 60 (1960),209.2. GOFFREDI, M. & SHEDLOVSKY, T., j. phys. Chem., 71(1967), 2182.3. SPIVEY, H. O. & SHEDLOVSKY, T., ]. phys. Chem., 71(1967), 2165.4. SELVARAJAN, V. M. & KALIDAS, C., Trans. SA EST, 9(1974), 111.5. KALiDAs, C. & SRINIVAS RAO, V., ]. chem . Engng Data,19 (1974), 201.6. CHRIST, O. & ELIAS, H., Chem. Ber., 99 (1966), 1.7. GALLANT, R. W., Hydrocarbon process., 46 (1964), 183.8. Fuoss, R. M., ONSAGER, L. & SKINNER, J. F., j. phys.Chem., 69 (1965), 2581.9. EVANS, D. F. & KAY, R. L., ].phys. Chem., 70 (1966), 366.10. EWELL, R. H.& EYRING, H.,].chem.Phys.,5 (1937), 726.11. BOLZAN, J. A. & ARVIA, A. J., Electrochim, Acta, 15(1970), 39.Stability Constants of Chelates of SolochromeDark Blue (Calcon) with La(III), Pr(III),Nd(III), Gd(III). Tb(III), Dy(III) & Ho(III)J. R. NARKHEDE & G. S. NATARAJAN*Inorganic Chemistry Laboratory, Laxrninarayan Instituteof Technology, Nagpur University, NagpurReceived 3 October 1974; accepted 7 April 1975The stability constants of 1: 1 complexes of solo-chrome dark blue (calcon) with a few lanthanides havebeen determined potentiometrically In aq, dioxane(50%, v!v) using the Irving Rossottl titration technique.SOLOCHROME Dark Blue (Calcon) has beenwidely employed as a complexometric reagent-,The compound in view of the hydroxy groups orthoto the azo group form well defined complexes withseveral metal ions2-4. Complexes of calcon (I) withLa(III) were first reported by Rehman et al.5• In*Present address: Max Plank Institute Fur Kohlenfurs-chung, 433, Mulheim, Ruhr, West Germany.NOTESOH HOHOJS N=NIthe present note, we have determined the stabilityconstants of the chelates of calcon with otherlanthanides in aq. dioxane employing Irving andRossetti" titration technique.Dioxane was purified by recommended procedure?Carbonate-free sodium hydroxide" (E. Merck, 0·4M)was standardized against solid potassium hydrogenphthalate (BDH AnalaR). Sodium salt of calcon(BDH) was purified as the corresponding acid bythe method of Langrnyhr". The purified sample wasstored in an anhydrous calcium chloride desiccator.Solutions of the ligand (0·005M) were obtainedby dissolving it in aq. dioxane (50%, vjv) andstandardized potentiometrically. Rare earth metaloxides (Indian Rare Earths, Kerala, purity> 99'9%)were used in the form of their nitrates for thepreparation of stock metal ion solutions in doublydistilled water. All metal ion stock solutions were0'00165M in 0'05M perchloric acid (Riedel, Germany)and their metal ion contents were estimated by thegravimetric methodl".Systronics pH-meter (type 322-1, accuracy ± 0·05pH units) using a glass calomel assembly calibratedat the working temperatures'! was used to measurethe apparent pH.The ligand to metal ratio was kept around 3:1in all titrations. All experiments were performedat 30°, 40° and 50° and at [1, = 0·1 (NaCI04) underoxygen-tree nitrogen presaturated with 50% (vjv)aq. dioxane.As one of the- OH groups of the reagent dissociatesat higher PH, the value obtained using the poten-tiometric method was checked spectrophotometri-cally=. Values of the formation functions nA, nandPL were calculated using the standard expressionss.The values of log pKr and log PK~ obtained from _the nA versus pH (meter reading) curves were refinedby (i) interpolation at half nA values and (ii) inter-polation at various nA values. Stability constantsTABLE 1 - STAl!ILlTY CONSTANTS AND t1F OF CHELATEFORMATION(Temp. 30°; (.I. = 0'1)MI+ log ](1 -t1Fkcal/moleLa 9·86 13·67Pr 10'47Nd 10'49 14·54Gd 11-52 15'97Tb 12'05 16·71Dy 11'94 16'55Ho 12'13 16'82131

Conductance of Hydrogen Halides in Diethylene Glycol at Different Temperatures

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Conductance of Hydrogen Halides in Diethylene Glycol at Different Temperatures

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