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1、 Colloidaldispersionsystem Classificationofdispersedsystembasedonparticlesize TypesofColloidaldispersion Lyophiliccolloids Systemscontainingcolloidalparticlesthatinteracttoanappreiableextentwiththedispersionmediumarereferredtoaslyophilic solvent loving colloids hydrophilicsols gelatin acacia insulin
2、 albuminLipophiliccolloids rubber polystyrene Amaterialthatformsalyophiliccolloidalsysteminoneliquid e g water maynotdosoinanotherliquid e g benzene Lyophobiccolloids Lyophobiccolloidsiscomposedofmaterialsthathavelittleattraction e g gold silver sulfur arsenoussulfide andsilveriodide Themethodstopre
3、parelyophobiccolloids Dispersionmethods1 grindingmethod2 sonicationdispersionmethod3 arcdischargemethodCondensationmethods1 physicalmethods2 chemicalmethods grindingmethod sonicationdispersionmethod arcdischargemethod Owingtotheintenseheatgeneratedbythearc someofthemetaloftheelectrodesisdispersedasv
4、apor whichcondensestoformcolloidalparticles Physicalcondensationmethods 1 replacementofsolvent Physicalcondensationmethods 2 Steamquenchmethod chemicalcondensationmethods 2H3AsO3 w 3H2S As2S3 sol 6H2OFeCl3 w 3H2O H Fe OH 3 sol 3HCl2H2S w SO2 g 2H2O 3S sol Na2S2O3 2HCl 2NaCl H2O SO2 S sol 2HAuCl4 3HC
5、HO 11KOH 2Au sol 3HCOOK 8KCl 8H2O Solpurification 1 dialysismethod2 ultrafiltration dialysismethod Semipermeablemembrane dialysismethod Electrodialysis ultrafiltration Semipermeablemembrane ultrafiltration Electroultrafiltration Associationcolloids CMC thecriticalmicelleconcentration CMC isdefinedas
6、theconcentrationofsurfactantsabovewhichmicellesformandalladditionalsurfactantsaddedtothesystemgotomicelles Typeofmicelle CylindricalmicelleBilayerBilayervesicleInvertedmicelleMicrotubule Classificationandtypicalexamplesofassociationcolloids Propertiesofsurface activeagentsshowingchangesthatoccurshar
7、plyattheCMC PredicttheCMCofthemixture Todeterminetheminimumamountofsurfactant Opticalpropertiesofcolloids scatteringoflight Lightscatteringisaformofscatteringinwhichlightistheformofpropagatingenergywhichisscattered Lightscatteringcanbethoughtofasthedeflectionofarayfromastraightpath forexamplebyirreg
8、ularitiesinthepropagationmedium particles orintheinterfacebetweentwomedia TheFaraday TyndallEffect Whenastrongbeamoflightispassedthroughacolloidalsol avisiblecone resultingfromthescatteringoflightbythecolloidalparticles isformed ThisistheFaraday tyndalleffect Ultramicroscope Anultramicroscopeisamicr
9、oscopewithasystemofilluminationthatallowsviewingoftinyparticles Whenthediameterofaparticleisbelowornearthewavelengthofvisiblelight around500nanometers theparticlecannotbeseeninalightmicroscopewiththeusualmethodofillumination Theultramicroscopesystemisbasedonlightscattering notlightreflection Ultrami
10、croscope Electronmicroscope Electronmicroscope capableofyieldingpicturesoftheactualparticles eventhoseapproachingmoleculardimensions isnowwidelyusedtoobservethesize shape andstructureofcolloidalparticles Kineticpropertiesofcolloids 1 Thermallyinduced Brownianmovement diffusion osmosis 2 gravitationa
11、llyinduced sedimentation3 appliedexternally viscosity BrownianMotion therandommovementofcolloidalpartocles ThefirstsatisfactorytheoreticaltreatmentofBrownianmotionwasmadebyAlbertEinsteinin1905 Diffusion DeducedbyEinsteinandStrokesWhereNAisAvogadro snumber Risthegasconstant isthecoefficientofviscosit
12、yofthesurroundingmedium ristheradiusofthesphericalparticle TistheabsolutetemperatureDiffusionisanentropyincreasingprocess Diffusion Osmoticpressure Sedimentation Inagravitationalfield heavyparticlessettletowardsthefootofacolumnofsolutionbytheprocesscalledsedimentation Whenasolutionisallowedtostand a
13、stateofequilibriumisfinallyreachedwhensedimentationanddiffusionbalanceeachother thatis wheninagivenintervaloftimetheamountofmaterialwhichfallsinthedownwarddirectionthroughaunitareaisthesameasthatwhichdiffusesupwardbecauseofthegreaterconcentrationatthelowerlevel sedimentation diffusion ultracentrifug
14、ation Sedimentationisnormallyveryslow butitcanbeacceleratedbyultracentrifugation atechniquethatreplacesthegravitationalfieldwithacentrifugalfield WhereRisthegasconstant Sisthesedimentationcoefficient theunitSvedbergis1X10 13second Tistheabsolutetemperature Disthediffusionconstant visthevolumeof1gofp
15、article isthedensityofmedium supercentrifuge Viscosity Viscosityisenexpressionoftheresistancetoflowofasystemunderanappliedstress Themoregreateristheappliedforcerequiredtomakeitflowataparticularrate ElectricalPropertiesofColloids ElectrokineticPhenomena ElectrophoresisElectroosmosisSedimentationpoten
16、tialStreamingpotential Electrophoresis Electroosmosis Sedimentationpotential Streamingpotential StabilityofColloidSystems KineticstabilitystableThermodinamicstabilityLyophobiccolloidsunstableLyophiliccolloidsstableAssociationcolloids DLVOtheory SensitizationandProtectiveColloidalAction Thepresenceandmagnitude orabsence ofachargeonacolloidalparticleisanimportantfactorinthestabilityofcolloidalsystems Sensitization theadditionofasmallamountofhydrophilicorhydrophobiccolloidtoahydrophobiccolloidofopp
