Jha, S. K.

Sharma, M. K.

Srivastava, S. N.

English

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indian .Jol1~nalof ChemIstryVoL 15A, March 1977,pp. 189-191Influenceof Methyl, Ethyl, Propyl & n-Butyl Alcohols onthe Stabilityof Oil-Water EmulsionsM. K. SHARMA, S. K. JHA & S. N. SRIVASTAVADepartmentof Chemistry,AgraCollege,Agra282002Received13 APril 1976;accepted11 July 1976The effectof methyl,ethyl,propyland n-butylalcoholson sodiumbenzylpenicillin-andchloramphenicol-stabilizedoil-water emulsionshas beenstudiedby measuringthe zeta-potentialsmicroelectrophoretically.In general,the zeta-potentialdecreaseswith increasingpercentageof alcohols.However,for thechloramphenicol-stabilizedemulsionsthereis a slightincreasein zeta-potentialin theinitialstages.Thechangesin zeta-potentialdueto theadditionof KNOs in thepresenceof differentamountof alcoholshavealsobeenexamined,andtheorderof flocculationconcentrationof KNOs has beenfoundto be n-butanol<propanol<ethanol<methanol.Theorderofeffectivenessofalcoholsin bringingabouta decreasein zeta-potentialis"n- butanol>propanol>"ethanol>methanol.ALTHOUGH quite a few referencesare avail-ablel-8 on the studiesof the interactionof. non-electrolyteson colloidalsols, in general,dataon thebehaviourof emulsionsin thepresenceof non-electrolytes are rather sparse. Someworkers7-1°have studied the sensitizationeffectand the adsorptionof some alcoholson Fe20a,AS20a,Fe(OH)sandothersols. GhoshandDharllhavereportedthe sensitizationeffectof sugaronAs20asol,whileMukherjeeandChaudhury12observeda decreasein the cataphoreticvelccitywhensugarwas addedto the sol and an increasein chemicaladsorption. Mukherjee13also measuredthe cata-phoreticvelocityin the presencecf ethanol,sugarandsomeelectrolytes,andtherest:ltswereexplain-ed on the basisof a doublelayer.In the presentpaperare reportedthe resultsofstudieson the interacticnof somealcoholssuchasmethanol,ethanol,prcpanoland n-butanolon theoil-wateremulsionsstabilizedby sodium benzyl-penicillinorchloramphenicol.Besidesthechangesinthe propertiesof thedispersionmediuman attempthas been madeto explain the decreasein zeta-potentialand its variationwith differentalcohclson the basisof adsorptionof alcoholmcleculesatthe surfaceof the oil globules.Materialsand MethodsPure samplesof sodiumbenzylpenicillin(AlembicChemicalgrade)and chloramphenicol(ParkeDavisgrade)wereused. Thealcoholsandotherchemicalsusedwereof Analar BDH grade.Emulsionswerepreparedby dispersing2% byvolumeof tolueneor xylene in aq. solution ofsodiumbenzylpenicillinandchloramphenicolsepara-telv. Toluenewasmadeheavierby addingchloro-foi'm. This has beenpractisedin similarsystemsto avoid creaming14. The final mixturealso con-tained O'OIM KCl. The mixturewas shakenfor30 min and finallyhomogenizedin a stainlesssteelhomogenizer(Fisher ScientificCo., USA). In alltheestimationsemulsicnswerepIeparedandsampledunderidenticalccnditionsso as to havemaximumpreCISIon.The electrcphoreticmobilitiesof the emulsion-globules were measuredmicroelectrcphcreticallyusing a Northrcp-Kunitz1/itype flat rectangularcell fitted in a speciallydesignedapparatus. Thediluted emulsicn was filled in the cell and·theelectrodechamberswerefilledwith an equiccnduct-ing potassiumchloridesolutionto avoid diffusicn.A constantdc voltagewasappliedacrossthe twosilver-silverchloride electrodes.Thepotentialgradientwasmeasuredby recordingthepotentialdifferencebetweenthetwo platinized-platinumelectrodesfusedat beth the endscf thecell chamberand so encasedthat cnly thier tipsprotrudedinto the cell chamber. PotentialsweIemeasuredwith thehelpof a vacuumtubevcltmeter(modelmajor, Electronic Prodllcts, India) using12 AU7 and 6 ALs vacuumtubes and havingimpendenceof 11 MQ on all ranges. The distancebetweenthese electrodeswas measureddirectlywith the help of a travellingmicroscope.The velocityof theparticles,asabservedthroughmicroscope,was timed for 3-5 divisicns cf thegraticule(1 div. =0·10[J.) calibratedagainstal'Ommstandardmicrcmeterscaledividedto 0·01mm.Knowingthepctentialgradient(E) andvelocity'(V) of the globules,the electrophcretic mobility(U) was calculatedusing the relaticnU=V/E ..,(1)Thus with the help of electrophoreticmobility,zeta-potentialof the systemwas calculatedusingHelmholtz18equationwhich is applicableto~hesystemsof sphericalparticlesand .xa~1.ResultsandDiscussionEffecto/alcoholsOnzeta-potential-Frem Table1it is evident that for sodium benzylpenicillin-189.~--~~-~INDIAN J. CHEM., VOL. 15A.MARCH 1977&0-3.5-5.5of small amounts of methyl and ethyl alcohols(Table 1). This initial increase may be attributedto the surfaceconductanceeffect. Further increasein the percentage of alcohols lowered the zeta-potentials as stated above.The alcohols with dielectric constant lower thanthat of water ECH,OH=33,EC.H,OH=24.Ec,H,oH=18'3,EC.H,OH=17and EH,O=78·5)should increasetheinter-ionic attraction in their aq. mixtures. The increasein interi ':lnicattraction can affect the existenceoffree polar heads (the hydrophilic end of the micellewhich is so vital for oil-water emulsionstability) be-ca'lse it is likely to suppressthe ionization of ionicemulsifiers. Further, likelihood of ion-pair formaticnis increasedand the polar headsforming the micelleare likely to be surroundedby ions (from ReI addedin the preparation of the emulsion and the ioniza-tion of emulsifiers) of the opposite charge. Thesefactors are thus likely to decreasethe emulsifyingactivity of both the emulsifiers with increasingalcohol content in the aq. mixtures and with thelength of the carbon chain for a given percentageofdifferent alcohols because dielectric constants arein the reverseorder of the chain length.The increase in interionic attraction shoddproduce reduction in zeta-potential and stabilityof the oil globules. In addition to this, as the con-centration of an alcohol is increased,its adsorptionat the surface of the oil-globules increases, theadsorption being greater the longer the carbonchain in the alcohol molecde. With increase inadsorption of an alcohol the number of moleculesof the emulsifier squeezedout of the surface of the20> 60e••...••N-••.•.•c:•~40Co-5.0 -4.5 -4.0Log [KN03 J, MFig. 1- Yariation of zeta-potential with [KN03J in thepresence of methanol for sodium benzylpenicillin-stabi-lized emulsion [(1) 5%. (2) 10%. (3) 15% and (4)20%MeOH]TAIlLE1_ ZETA-POTENTIALSANDMOBILITIESASFUNCTIONOFALCOHOLPERCENTAGEAlcohol IA B%Ux lOt1.:Ux lOt:(emsec-lY-I)(mY)(emseel -I)( )METHANOL2,5404471,934,0565'615·0, 96 28· 67 398,3 6·4 15103- 75 -730 22·724 060117 5-2·792 ·505 42 75·0- 33830·'3 7 0ETHANOL2·5'329-85 0· 88,-1142 53 1482 ·0 9-35,005PROP 1·522·55 0610·12 ·08' 7n-BuTANOL1·02·02'5, 2,"512·55 012750·'Asodiumb nzylpenicillin-stabilizedemulsion;andB=loramph nicol-stabilizedemulsion.stabi ized emulsionszeta-potentialdecreasessharplyup tne rly 15% of lcohol c::mcentrationfollowedby a mall but gradual decreaseon further additionof al ohol with a clear t ndency of pproaching alimit ng value. The m gnitude of decreasein zeta-pote tial was greate in the case higher alcohol.Thupercentageof an alc hol required for gettingtheame agnitude of decreasei zeta-p tentialwasreater for the lower alcohol.Th order feff ivenesshas been found to be n-but n l>p o-an> th o >methanol.FchIoramph nicoI-st bilizedmulsio sth rwasslig t inc eas z ta-p tential n he addition190SHARMA etal.: INFLUENCE OF ALKANOLS ON THE STABILITY OF OIL-WATER EMULSIONSoil-globules increases and so the zeta-potential islowered further.Effectof electrolyteson zeta-potentialin thepresenceof alcohols- The variation in zeta-potential dueto the addition of KNOa in the presenceof methylalcohol is shown in Fig. 1. The nature of the curvesin the presenceof othe' alcohols is identical to thatobtained in the case of methyl alcohol. The de-crease in dielectric C'lnstant favours attractionbetween the oppositely charged species. Thusaddition of alcohols should bring about an increasein attraction forces between the charged sites onthe surface of the emulsion globules and oppositelychargedions in the solution, i.e. Rot;in the presentcase. The higher the alcohol greater will be thisattraction. This explains the following order offlocculation concentration of RNOa: n-butanol <propanol<ethanol<methanol.AcknowledgementThe authors wish to express their thanks to thePrincipal for providing facilities and also to theCSIR, New Delhi, for the award of a post-doctoralfellowship to one of them (M.K.S.).References1. MATSUMO, Y, Biochem.Z., 150 (1924),139, 160.2. FREUNDLICH, H. & LOEBMANN, S.; Brit. Chem.Abstr.,(1929),A 263.3. CHAUDHURY, S. C. & GANGULI, A., J. phys. Chem.,32(1928),1872.4. FREUNDLICH, H. & LOEBMANN, S., Z. phys. Chem.,139(1928),368.5. CHAKRAVARTI, K. & GHOSH, B. N., J. Indian chern.Soc.,41 (1964),559.6. YADAV, B. P. & CHATER]EE, A. C., J. Indian chem.Soc.,21 (1944),227.7. FREUNDLICH, H. & RONA, P., Biochem.Z., 81 (1915),87.8. PRASAD, M. & DHAR, N. R, J. Indian chem.Soc., 10(1933),53.9. WEISER, H. B., J. Phys. Chem.,28 (1924),1253.10. PATEL, A. R & DESAI, Kolloid-Z., 51 (1930),318.11. GHOSH, B. N. & DHAR, N. R, J. phys. Chem.,29 (1925),668.12. MUKHERJEE, J. N. & CHAUDHURY, S. G., Sci. Cult.,1(1935),111.13. MUKHERJEE, J. N., Trans. Faraday Soc., 16 (1921),203.14. SASTRY, T. G. & SRIVASTAVA, S. N., Indian J. Chern.,6 (1968),728.15. NORTHROP, J. H. & KUNITZ, M., J. gen. Physiol., 7(1926),929.16. HELMHOLTZ, W., WElD, Ann. Phys., 7 (1879),337.191

Influence of Methyl, Ethyl, Propyl & n-Butyl Alcohols on the Stability of Oil-Water Emulsions

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Influence of Methyl, Ethyl, Propyl & n-Butyl Alcohols on the Stability of Oil-Water Emulsions

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