Bassi, P. S.

Sharma, I. B.

English

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NOTESTABLE 1- VALUES OF ELECTROKINETIC POTENTIAL, NUMBEROF MOLECULES ADSORBED, Vlr3, FACTOR F AND SURFACEEXCESS WITH DIFFERENT CONCENTRATION OF ANIONICSURFACTANTS[Sur- Electro-nX 10-13rs X 1010Vlr3Ffactant]kinetic g/cm2(M)potential(mV)SODIUM CAPROATEl'Oxl0-6 28'320'250·0425'50408'Ox 10-63 ·21713· 52·0X '06·691- 14 4 55, 315·902-19 8'1 l0-262 ' 34 836 01, 8l'5xl0-169 53 70'SODIUM LAURATE1'0X 10-6.,-25 526 51 7435x97 3,SODIUM LAURYL-BENZENESULPHONATE1·0x10-67-8'8- 429· 'SODIUM DIOCTYLSULPHO CCINATE1·0x 10-6to·OO 4O l -4604··l' 31 2minima,whicharesufficientlydeep(roughlyequalto15 kT) for reversibleflocculation,is observed.Thanks are due to CSIR, NewDelhi, for theaward of post-doctoralfellowshipto one of theauthors(M.K.S.).References1.SHARMA, M. K & SRIVASTAVA, S. N., Indian]. Technol.,12 (1974),518.2. JAIN, S. P. & SRIVASTAVA, S. N., Indian]. Chern.,8(1966),544.3. BAHADUR, P., SHAMRA, M. K. & SRIVASTAVA, S. N.,CelluloseChern.Technol.,8 (1974),387.4. KUNDU, L., J. Indian chern.Soc.,47 (1970),913.5. SHARMA, M. K. & SRIVASTAVA, S. N., CelluloseChern.Technol.,10 (1976),235.6. SHARMA, M. K. & SRIVASTAVA, S..N., Indian]. Technol.,13 (1975),419.7. PHILLIPS, J. N. & RIDEAL, E. K, Proc. R. Soc., A232(1955),159.8. DAVIS, J. T. & RIDEAL, E. K., InterfacePhenomena(Academic Press, New York), 1963,186.9. DAVIS, J. T., Proc. R. Soc.,A245 (1958),417.10. BECHER, P., Emulsion theoryand practice (Reinhold,New York), 1965.11. SRIVASTAVA, S. N., Z. phys. Chern.,233 (1966),237.12. LEATHES, J. B., J. physiol.,58 (1923).13. LEATHES, J. B., Lancet, 1 (1925),853.14. HNAI, T., HAYDON, D. A. & TAYLOR, }., Prac. R. Soc.,A281 (1964),377; J. Theoret.Bioi., 9 (1965),278,422,433.15. WOODMAN, R. M., J. Soc.chern.Ind., 51 (1932),95T.16. WOODMAN, R. M., J. Soc.chern.Ind., 54 (1935),70T.17. JAIN, K D. & SHRMA, M. K, Res.& Ind., 16 (1971),128.18. MATIJEVIC, E. & PETHICA, B. A., Croat. Chern.Acta,29 (1957),431.19. PERREIRA, H. C., ]. colloidSci., 20 (1965),44.20. Internationalcritical tables,Vol. IV (McGraw-Hill, NewYork), 1929,435.Kineticsof ReactionBetweenCopper&Iodinein the Solid StateP. S. BASSI & I. B. SHARMADepartment of Chemistry, University of JammuJammu 180001Received9 August1976;accepted2 February1977The kineticsof the solid statereactionbetweencopper (plates) and iodine (solid and vapours)havebeenstudiedin thetemperaturerange303-343°K.The reactionis diffusion-controlledandthekineticsfollow parabolicequation.The chemicalanalysisandX-raydiffractionstudiesindicatethattheproductformedis 'Y-CuI.IN thetarnishingof metals,whentheproductfilmsarecoherent,generallytwotypesof filmgrowthshave been observed,viz. thick and thin filmgrowthsl-4.The thick film growth is governedby thediffusionof the reactionspeciesandusuallya parabolicequationis applicable,thoughinstancesof deviationfrom parabolicrate equationare alsoavailable4,5. In the thin film growth,the develop-ment of the product film takes place under apotential gradientdevelopedbetweenthe metalatomsandthe adsorbedgas. A logarithmic,cubicor a fourthpowerlaw is applicablein this case.Parabolicgrowthof the productlayerhas beenreportedin a kinetic study6of the iodinationofcopperby iodine(vapour)in thetemperaturerange404-573°K at differentpressures.In the presentinvestigationtarnishingof copperby iodine (solidand vapour)at differenttemperatures(303-343°K)at saturatedvapourpressureshasbeenstudied.Copper(AR) platesof equalsize (4·00 cm2) cutfrom copperfoil wereusedafter treatmentas de-scribed earlier3.Iodine (AR) powder was usedas such.Copper (Plates)-iodine (solid) reaction- Copperplateswereinsertedin iodinepowderin separateglassvessels.A constantpressurewas appliedonall the vesselswhichwereplacedin a thermostathaving an accuracyof 0·1°K. Each plate wasremovedafter a certainintervalof time and wasfoundto becoveredwith a verythin internallayerof product and anotherthick outer layer. Theouterthick layerwasremovedby tappingwhiletheinternalthin layerwasremovedby treatmentwith5% KI solution in which it is soluble7• Theunreactedcopperplates were washed,dried andweighed.The loss in weightgave the weightofcopperreacted.649---- _. _ ..-_._--~322824o1684-+-12 13 20TIME (hrlFig. 2- Plotsof W' versustimeat differentemperaturesforthereactionbetweencopper(plates)andiodine(vapour)500300x1000Nen1500100,n'08 121'-IME (hr)Fig. 1- Plotsof W' versustimeat differentemperaturesfor the reactionbetweencopper(plates)and iodine(solid)'" .~2009·50 and 13·2 kcaljmolerespectively.The para-metersof the Eq. (1)aregivenin Table 2.The averagemaximumthicknessesof theproductfilms in copper-iodine(solid) and copper-iodine(vapour)reactions,calculatedfrommassandtheore-Reporteddatafor y-CuId(nm)0,3493(100)0'3025(12)0·2139(56)0·1824(34)0·1747(5)0·1512(7)0·1388(11)0·1353(9)0·1235(10)0·1164(7)0·1069(3)0·1022(6)0·1008(1)0'0957(3)0·0923(2)0·0842(4)0,0809(1)PreseJittstudyd~nm)Intensityvaluesareenclosedin parentheses.650TABLE 1-X-RAY DIFFRACTION DATA OF THE REACTIONRODUCTAND THE REPORTED DATA FOR y-CuIINDIAN J. CHEM., VOL. 15A. JULY 1977Coppe (Plates)-iodine(vapou,r)reaction- Copperplates (·00 cm2 size) were treatedas describedearlier3nelsuspended,throughholeselrilledin them,to plati urn hangersin glassreactionvesselseachfilledw' h 10g of iodinepowderand placedin athermosat kept at a constanttemperature.Theplates id not touch the solid iodinewhile iodinevapours at saturationvapour pressure,were incontactwith the plates. Each platewas removedafter a certain interval of time and weighed.The inc easein weightgavetheweightof theiodine(vapourreacted. It wasobservedthatthereactioninitially takesplaceat the edgesof the plateandultimatly movesto the wholeof the surface.Kno n quantitiesof the products(outerthicklayer) rmedin copper-iodine(solid)and copper-iodine vapour)reactionswereanalysedfor copperby the sualiodometricmethod. Theresultssuggestthatth compoundformedin boththecaseshasthestoichi etric formulaCuI.The dentityof the outer (thick product)layerwas fu ther confirmedby X-ray diffractionstudiesusing -KCJ(radiation. The X-ray diffractiondataof the productsof the copper-iodine(solid) andcopper-odine (vapour) reactions (which exactlyresembedeachother)arein fair agreementwiththeknownX-ray diffractiondata of '(-CuP (Table1).The in nsitiesof theexperimentallinesweredeter-mined y visualreading. The innerproductlayerwasve y thin andcouldnot be analysedeitherbygravimtric methodor by X-ray diffractionstudies.Eq. 1) is foundto fit the kineticdataboth. forcopper'odine (solid) and copper-iodinc(vapour)systemW!= 't+C ...(1)Thc v ueof the constantC, is zeroin the caseofcopperiodine (vapour)r(action. The applicabilityof the equationis shownin Figs. 1 and 2.For pper-iodine(solid)andcepper-iodine(vapour)reactios, the valuesof the energyof activation,caJculaedfromthe Arrheniusplots,comeoutto beNOTESReactionsof AnhydrousInorganicNitratesinDimethylformamide-AcidChlorideAdductsTABLE 2- PARAMETERSOF Eg. 1 FOR THE REACTIONBETWEENCOPPER(PLATE)AND IODINE (SOLIDANDVAPOUR)AT DIFFERENT TEMPERATURESInorganicnitratesexchangeanionwith dimethyl-formamide-acidchlorideadductsformingnewadducts.Theseintermediatesareveryunstableand,decompos~R. RAO KOGANTY & M. M. BOKADIADepartmentof Chemistry,Vikram University,Ujjain 456010Received9 July 1976;accepted5 February 1977ACID halideadductsof dimethylformamide(DMF)andtheirreactionshavebeenreportedearlier1,2.The adductsgenerallyexistin equilibriumwith freeDMF and acid halides(Eq. 1). Adducts (I) arevery reactivedueto the presenceof -C=N bondwhichis highlysusceptibleto nucleophilicreagents2.[ +/CH3]RCOCl+HCO-N(CH~)z "'. R-CO-CH=N Cl-'H(I) ." (1)[ +/CH3]R-CO-O-CH=N NO.. '.(II)In orderto understandthenatureof anionin theadduct(I), aninvestigationhasnowbeencarriedoutto exchangethe anionwith morecomplexoxyacidanion such as nitrate. The exchangeoccurredspontaneouslywhensodium,potassiumor calciumnitratesareused. But ammoniumandsilvernitratesreactedinstantaneouslyaccompaniedby thedecom-positionof·the newadduct(II). However,decom-positionmaybeavoidedby keepingthetemperatureat 0°. The exchangeis alwaysfollowedby preci-pitationof metalchloride.The reactivityof thesalt seemsto dependon thecationicpart. 'The-novel aspectof the exchangereactionis the sU8sequentdecompositionpatternof the adduct (II). The adduct (II) decomposesspontaneously.The structurefor II is attributedon the basis of adduct (I) whose structureisknown1,2.SimilarstructureshavebeenassignedtoDMF-Lewis acid adducts3,4.Adduct (II) differsfrom the other adductsofDMF so far known in that it possessesa morecomplexoxyacid anion. The instability of theadduct (II) may be attributedto the degreeoffreedomofoxyacidanionitself. Mostaproticdipolarsolventslike DMF strongly interact with ionicLewisacidtypeofcompounds.Usuallyit is cationicpart that is more firmly held by the dipolarmolecule.Thepositiveendof dipoleis lessaccessibleandhencethe anionof the Lewisacid is relativelyfree to be very reactive5• For this reasonthereactivityof the anionicpart of II is responsiblefor the instabilityof the adductas a whole. Theexistenceof the anion in a non-aqueousmediummayhavepartiallycontributedto the instabilityofthe adduct.Ingold6,7 observedthat the nitrating power ofany acyl nitrate is due to the existenceof anequilibrium(Eq. 2) and that it is the N205that2R-CO-0-N03+---+(R-CO)zO + NZ06 •••(2)nitratesratherthan acyl nitrateitself. Normally,fornitration,N0'2is necessarywhichis notgeneratedin thedecompositionof adduct(II). This accountsfor the failureof II to nitrate anisol,while acylnitrate accomplishesthe reactionwith ease. Thecourseof decompositionof II is givenin Eq. (3).2(1I)---+ (RCO)zO + 2DMF+! Oa.+ NaO, •..(3)in anexothermicreactionevolvingNzO, andoxyl1en.Thesereactionsmayserveasan insitusourceofoxygenin a nonaqueousmedium.2'006'0514'0025'5036·00Kxl06(gZ/hr)COPPER-IODINE(SOLID)SYSTEM2-995'679'3311-5714-61COPPER-IODINE(VAPOUR)SYSTEM303 3'00313 11-63323 21'62333 39'58343 71,87303313323333343ticaldensityof theproductfilmsandthedimensionsof the metalplate, are 0·0030em and 0·0043<;mrespectively.In this thicknessrangeof coherentproductfilms,the parabolic·equationis obeyed1,2.Another condition for the applicabilityof theparabolicequationis low condltctivityof reactionproduct, which is satisfiedin this case'. Thereactionsbetweencopperand iodine (solid) andcopperandiodine (vapour)arediffusion-controlled,wherethe diffusionof reactingspecic:sdeterminesthe rateof the reaction. The film is coherentandprotectiveand controlsthe diffusionin the courseof reaction. The agreementbetweenthe presentexperimentaland the earlierreportedvalues6(12'4kcaljmole)of the energyof activationsuggeststhat the reactionmechanismat highaswell as theordinarytemperatureis the same.One of the authors(LB.S.) is thankful to theCSIR, New Delhi, for the awardof a post-doctoralfellowship.References1. HARDEL, K., AngewChem. intern. Edn, 11 (1972),173.2. CABRERA,N. & MOTT,N. F., Reportsonprogressin physics,Vol. 12 (The Physical Society,London), 1949,163.3. BASSI,P. S. & SHARMA,1.B., Indian J. Chem.,14A (1976),692.4. BASSI,P. S. & SHARMA,1. B., Indian J. Chem.,12 (1974),813.5. EVANS,U. R., Pittsburghintern.conf.on surfacereaction,1948,71.6. SUIGIER,H., Nukeonika,12 (1976),471.7. MELLOR,J. W., Inorganicand theoreticalchemistry,Vol. 3(Longmans,Green, London), 1952,203.8. SMITH, J. V., X-ray diffraction data card No. 6-0246(AmericanSociety for TestingMaterials,Philadelphia),1962.651

Kinetics of Reaction Between Copper & Iodine in the Solid State

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Kinetics of Reaction Between Copper & Iodine in the Solid State

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