tic mixtures containing NaN02 and [FelI(CN)sH20P-prepared by Hofmann's- method in three differentproportions. It will be seen that in the case of thesesynthetic mixtures also, [FeTI(CN)5H20]S- is oxidisedfirst, followed by the oxidation of NO;- in the. nextstep, and the amounts ofpermanganate which are usedup in the two steps are as required by the composi-tions of the synthetic mixtures. Furthermore, theO.D. at 395 nm increases as [FeU(CN)5H20P-is oxidised, as found in the case of the photo lysedsolutions.

References1. MITRA, R. P., ~ATN, D. V. S., BANERJEE, A. K. & CHARI,

K. V. R., J. tnorg: nucl. Chem., 25 (1963), 1263.2. MITRA, R. P., SHARMA, B. K. & MITTAL, S. P., J. inorg.

nucl. Chem., 34 (1972), 3919.3. BUXTON, G. V., DAINTON, F. S. & KALECTNSKI, J., Int.

J. Rad. Phys. Chem., 1 (1969), 87.4. WOLFE, S. K. & SWINEHART, J. H., Inorg, Chem., 14

(1975), 1049.5. LODZINSKA, A. & GOGOLlN, R., Roczniki Chem., 47 (1973),

881.6. ASPERGER. S., MURATI, I. & PAVLOVIC, D., J. chem. Soc.,

(1960), 730.7. MOGGI, L., BOLLETTA, F., BALzANT, V. & SCANDOLA, F.,

J. inorg . nucl. Chem., 28 (1966), 2589.8. HOFMANN, K. A., Liebig's Ann., 312 (1900), 1.9. LATIMER, W. M., Oxidation potentials (Prentice-Hall, Inc.

New York) 1952, 93.

Thermodynamics of Mixtures Containing Dioxane orTetrahydrofuran -Analysis of Excess ThermodynamicProperties of Binary Solutions in Terms of Flory's

Theory]

S. L. OSWAL

Department of Chemistry, South Gujarat University,Surat 395 007

Received 8 February 1979; accepted 12 March 1979

The segment model of Flory's theory of solutions is used toanalyse our previously published data for the thermodynamic pro-perties of a number of solutions containing dioxane or tetra-hydrofuran. It has been found that the Flory's theory gives afairly good description of the results on the systems inspite of thefact that in some of the solutions specific interactions are pre-dominant.

FLORY and coworkers-? have developed thestatistical theory for mixtures of nonpolar

molecules differing in size and shape. This theoryhas successfully correlated excess properties of anumber of solutions>". In the present paper theanalysis of our data7,8 on excess Gibbs free energy(GE), excess enthalpy (HE) and excess volume (VE)for ten binary solutions of dioxane or tetrahydrofuran(THF) with cyclohexane, n-heptane, benzene, toluene,and carbon tetrachloride has been made in terms ofFlory's theory.

tThis work forms part of author's Ph. D. thesis submittedto lIT, Bombay, 1973

I

NOTES

The following relations are used to obtain HE,GE and VE.

i=2

HE = L XiP:i=l

v~ ( V;l_ V-I) + XIV: 82XUV-1...(I)

i=2

GE = I xip:i=l

v* [(Vi-1)- v-I)+3Ti In (_~1_1_3_1--=.)J' (VIIS -1)

In Eqs (I) and (2) X12 is a constant characterizingshe difference in the energy of interaction betweentites on neighbouring molecules of species 1 and 2,and the average of interactions in the pure componentliquids.

The values of the properties, 1', CI. and v of purecomponents at 303.15 K alongwith the correspondingvalues of characteristic parameters v'\ T* and P*are summarised in Table J. The required data ondensity, thermal pressure coefficient, isothermalcompressibility were taken from Timmerrnanns", Abeand Flory", Diaz-Pena and McGlashanlo, Deshpandeand coworkers=P for the calculations of CI. P* v*and T*. In the absence of direct data on'the;malpressure coefficient (y), it was calculated by Eq. (4).

y = (ap/anv = CI./k ... (4)

where k is isothermal compressibility.In the evaluation of excess functions, using Flory's

model, the knowledge of the parameter Xl2 isnecessary. It is an adjustable parameter and can becalculated from the best fit of either HE or VE data>".Using this value of X12, other excess functions can bepredicted. In the present investigation, experimentalVE data were used to evaluate the parameter Xl2•Xl2 should be a constant, independent of composi-tion. However, it was found that X12 varies with theconcentration. The least square average value ofXl2 from VE data over entire range of compositionwas obtained and used in the calculation of GE, HEand VE. These results at equimolar compositions arereported in Table 2.

The HE values calculated for the systems cyclo-hexane + THF and benzene + dioxane agree wellwith experimental data while for the system cyclo-hexane + dioxane the agreement is within 6 % andfor carbon tetrachloride + THF it is about 10%.For the systems carbon tetrachloride + dioxane andbenzene + THF the difference between calculatedand experimental HE is considerable.

The GE values calculated using X12 obtained fromthe best fit of VE, agree very well with the experimen-tal GE for the two systems n-heptane + dioxaneand l1-heptane -I- THF, while the agreement is within10% for the system cyclohexane + dioxane. Forthe other systems the predicted GE values are much

353

rINDIAN J. CHEM., VOL. 18A, OcrOBER 1979

TABLE 1 - PROPERTIESOF PURE LIQUIDSAT 303.15 K

Liquid ct X 10', - v* T* p*,v, v ,crns mole-s K-l ern" mo16-1 K J cm~3

Dioxane 86.19 1.105 1.2725 67.74 4997 716.9Tetrahydrofuran 82.24 1.213 1.2938 63.57 4768 646.3Cyclohexane 105.41 1.233 1.2975 84.33 4730 529.3n-Heptane 148.39 1.260 1.3026 133.99 4674 426.8Benzene 89.95 1.233 1.2975 69.33 4730 623.4Toluene 107.43 1.081 1.2677 84.74 5056 542.5Carbon tetrachloride 97.68 1.245 1.2998 75.16 4708 564.8

TABLE2 - COMPARISONOF RESULTSOF FLORY CALCULATIONSWITH THE EXPERIMENTALVALUESFOR EQUIMOLARMIXTURESAT 303.15 K

Flory parameters GEIJ mol-l HE/] mol-l VE/cm3 mo\-l

Xu, Qux 10', Expl Calc. Calc. ExpJ Calc. Expl. Calc.J cm-3 J cm-8 K-l (ref. 7, 8) (Eq. 2) (Eq. 5) (Eq. 1) (ref. 8) (Eq. 3)

BINARYSOLUTIONWITH DIOXANE

79.3 2.08 1006 1120 1005 16018 1514 0.945 0.94962.0 0.42 932 958 934 0.749 0.759

-1.7 -1.61 64 -18 63 -32a -32 -0.070 -0.092-3.6 -3.35 135 -51 133 -0.013 -0.018-7.7 -5.59 187 -99 187 -225b -145 -0.238 -0.230

Component

CyclohexaneII-C.Hl•C.H.TolueneCCl,

BINARYSOLUTIONWITH THF

Cyclohexane 39.1 2.75 379 523 376 736· 718 0.551 0.557II-C,Hn 24.8 0.0 360 361 361 0.405 0.419C.H. -21.7 -2.90 -131 -274 -130 -270d -376 -0.270 -0.271Toluene -31.6 -5.60 -130 -429 -130 -0.342 -0.347CCl, --44.8 -8.64 -141 -581 -142 -736- -798 -0.600 -0.611

(a) Reference 15; (b) reference 19; (c) reference 16; (d) reference 17; and (e) reference 18.

lower than the observed ones except for cyclohexane+ THF system where it is higher. This departure ofGE from the experimental value is attributed to thefact that X12 is energetic in origin. In general, theinteractions between neighbouring species mayreasonably be expected to effect the entropy also-".Therefore, it is necessary to consider the contributiondue to interaction entropy, in order to get an agree-ment between calculated and experimental GE.Flory in his later papers, introduced a term inEq. (2) for the interaction entropy which by analogywith the term in XI2 takes the form, 02XIVI*TQ12'Thus the modified equation for GE is

i=2 (yt/3_ 1)GE " Xi P; v7 [(v-:-I_V-I)+3 t: In _t ]

~ • (V1/3 -1)1=1

where QI2 is a parameter for entropy contributiondue to contact interactions. It is obtained from thebest fit to experimental GE data using the same valueof X12 obtained earlier. The values of Q12 are alsoincluded in Table 2 for all the systems.

The parameter X12 takes into account (i) positivecontribution due to dispersion forces, (ii) positivecontribution due to orientation forces and (iii)negative contribution due to dipolar forces':', In the

354

(

present study the parameter X12 is high and positivefor systems cyclohexane + dioxane, n-heptane +dioxane, cyclohexane +THF and n-heptane + THF.For all the other six systems studied here, X12 isstrictly negative in the following order benzene< toluene < carbon tetrachloride for dioxaneas well as for THF solutions. The negative XI2suggests that in these six systems, the unlike pairinteraction is much lower than the interaction bet-ween like pairs, i.e. specific solute-solvent interac-tion due to the dipolar forces is predominent over thedispersion and orientation forces. That Q12 is nega-tive for the systems of benzene, toluene, carbontetrachloride in dioxane or THF again supports thesolute-solvent specific interaction in these solutions.

Considering the very simple equation of state onwhich Flory's theory is based, the properties of thesystems considered here are correlated fairly wellby it.

The author expresses his thanks to Prof. D.D.Deshpande, lIT, Bombay for his valuable guidance.

References1. FLORY, P. J., J. Am. chern. Soc., 87 (1965), 1833.2. ABE, A. & FLORY, P. J., J. Am. chern. Soc., 87 (1965),

1838.3. BENSON, G. C. & JASWANT SINGH, J. phys. Chem., 72

(1968), 1345.4. ABE, A. & FLORY, P. J., J. Am. chem. Soc., 88 (1966),- 2887.5.0RWOLL, R. A. & FLORY, P. r., J. Am. chem. Soc., 89

(1967), 6822.

r6. BA'ITINO, R., cne« Rev., 71 (1971), 5.7. DESHPANDE,D. D. & OSWAL,S. L., J. chem. Soc. Faraday

Trans. 1., 68 (1972), 1059.2. DESHPANDE,D. D. & OSWAL, S. L., J. chem. Thermodyn.,

7 (1975), 155.9. TIMMERMANS,J., Physico-chemical constants of pure organic

compounds (Elsevier), 1965.10. DIAZ-PENA, M. & MCGLASHAN, M. L., Trans. Faraday

Soc., 57 (1961), 1511.11. DESHPANDE,D. D. & BHATGADDE,L. G., J. phys. Chem.,

72 (1968), 261.12. DESHPANDE,D. D., BHATGADDE,L. G., OSWAL, S. :C. &

PRABHU,C. S., J. chem. Engng Data, 16 (1971), 469.13. GUGGENHEIM,E. A., Mixtures (Oxford University Press,

London), 1952.14. DESHPANDE, D. D. & PRABHU, c. S., Indian J. Chem.,

16A (1978), 95.15. ANDREWS, A. W. & MORKOM, K. W., J. chem. Tliermo-

dyn., 3 (1971), 513.16. ARM, H. & BANKAY,D., Helv. chim. Acta, 52 (1969), 279.17. ERVA, J., Suomen Kemi., 28B (1955), 131.18. DINCER, S. & VAN NESS, H. C., J. chem. Engng data, 16

(1971), 378.19. McKINNON, I. R. & WILLIAMSON,A. G., Aust. J. Chem.,

17 (1971), 1374.

Thermal Behaviour of Silver Chlorate

M.R. UDUPA

Department of Chemistry, Indian Institute of Technology,Madras 600036

Received 2 February 1979; accepted 16 March 1979

The thermal decomposition of silver chlorate has been followedby TG, DTA, IR spectroscopy and X-ray powder diffractionstudies. The results suggest that a part of silver chlorate getsoxidized to silver perchlorate during the decomposition and thefinal product is found to be silver chloride.

THERMAL behaviour of alkali metal chloratesrevealed that they were congruently melting anddecomposed to metal chlorides':". During decompo-sition, a part of the chlorates underwent dispropor-tionation to perchlorates and chlorides':". Recentlywe have studied the thermal behaviour of TlCI03(ref. 4) and KCI03 (ref. 5). Silverer) resembles alkalimetals and thallium(l) in some of its crystallo-chemicalbehaviour. It is therefore, interesting to study thethermal behaviour of silver chlorate and compare itwith that of alkali metal and thallium(l) chlorates.The decomposition studies are followed by TG,DTA, IR spectral measurements and X-ray powderdiffraction patterns.

Silver(l) chlorate was prepared by mixing equalvolumes of aqueous solutions containing equimolarratios of silver sulphate and barium chlorate. Theprecipitated BaS04 was filtered and the clear solutionevaporated on a wg.ter-bath. AgC103, thus obtained,had dhkl values (A), 2.90s, 3.0Im, 3.43m, 4.25m,which agreed" with the reported values.

The TG studies were made in air using Stantonrecording thermobalance and DTA in air on a Netzschdifferential thermal analyzer. The X-ray powderdiffraction patterns were taken with a Debye-Scherrer

I

NOTES

(b)

EJ(O

II

ENOO

soo 700 300 500 100Temperature. ~

Fig. 1 - TG plot (a) and DTA plot (b) of AgCIOa

camera of 0.1l46m diam., using CuKcx. radiation.The IR spectra were recorded in KBr in the range1400-600 em'? on a Perkin Elmer 257 spectrometer.

The TG curve of AgCI03 obtained by heating at6°C mirr ' is given in Fig. la and it indicates that thedecomposition starts at 443K and is complete around525K. The mass loss of 26 %, observed from the TGcurve (expected 25.1 %) corresponds to the formationof AgCl. This is confirmed by the chemical analysisof silver content in the residue (Found : Ag, 74.6.Reqd : Ag, 75.3 %). Further the X-ray powderpatterns of the product gave the d"kL values, 1.96 rn2.77s, 3.20s which agreed? with those of AgCl. Onclose observation of the TG curve, it is apparentthat there are two stages of decomposition, the firstcommencing at 443 and completing around 493K.The second stage overlaps on the first and completesby 525K.

In order to find out the intermediates of decomposi-tion, a known amount of AgCI03 was heated to473K and when the reaction just initiated, the mixturewas withdrawn from the furnace. The product wasfound to be fused and its IR spectrum was comparedwith those of free AgCI04 and AgCI03• The par-tially decomposed AgCI03 had absorptions ,...,1100,characteristic of '1Cl-O of perchlorate and 970s,945 cm-1 due '1CI-O of chlorate". This clearly suggeststhat during the decomposition a part of chlorate isoxidized to perchlorate ("Cl-O "'" 1100 cm-l),an observation similar to that found in the case ofalkali metal and thallium(I) chlorates.

The DTA plot (Fig. 1b) suggests that the decomposi-tion starts with an endothermic reaction at 493Kwhich is immediately followed by an exothermicprocess at 523K. The endothermic effect may be at-tributed to the combined effect of fusion of AgCI03and formation of AgCI04 which is followed byexpulsion of oxygen in the exothermic effect to giveAgCl as the final product.

References1. MARKOWITZ, M. M., BaRYTA, D. A. & STEWART, H.,

J. phys. Chem., 68 (1964), 2282.2. FREEMAN,E. S. & RUDLOFF, W. K., Differential thermal

analysis, edited by R. C. Mackenzie (Academic Press,London), 1970, 364.

3. SOLYMOSI,F. & BANSAGI,J. Acta chim. Acad. Sci. Hung.,56 (1968), 357.

4. UDUPA, M. R., Thermochim. Acta, 16 ; 1976), 182.5. UDUPA,M. R., Indian J. Chem., 15A (1977), 556.

355