States of Matter and properties of matter

This PDF file content is about States of matter and its Properties as per the PCI syllabus for B.Pharm Second year for the subject Physical Pharmaceutics

1. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa

2. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa

3. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
All matter exists in three states:

4. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Agasconsistsofmoleculesseparatedwideapartin
emptyspace.
Themoleculesarefreetomoveaboutthroughoutthe
container.
Aliquidhasmoleculestouchingeachother.
However,theintermolecularspace,permitthe
movementofmoleculesthroughouttheliquid.
Asolidhasmolecules,atomsorionsarrangedina
certainorderinfixedpositionsinthecrystallattice.
Theparticlesinasolidarenotfreetomoveaboutbut
vibrateintheirfixedpositions.

5. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Changes in the States of Matter

6. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Liquefaction of Gases
Criticalphenomenon
Criticalconstants
Methodsofliquefactionofgases

7. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
CriticalPhenomenon
Agascanbeliquefiedbyloweringthetemperatureandincreasing
thepressure.
Atlowertemperature,thegasmoleculeslosekineticenergy.The
slowmovingmoleculesaggregateduetoattractionsbetweenthem
andareconvertedintoliquid.
Thesameeffectisproducedbytheincreaseofpressure.Thegas
moleculescomecloserbycompressionandcombinetoformthe
liquid.
Andrews(1869)studiedtheP-Tconditionsofliquefactionofseveral
gases.
Heestablishedthatforeverygasthereisatemperaturebelowwhichthe
gascanbeliquefiedbutaboveitthegasresistsliquefaction.This
temperatureiscalledtheCriticalTemperatureofthegas.

8. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
T
c,P
c,andV
carecollectivelycalledas
theCriticalConstantsofthegas.
CriticalTemperature,T
c:Thecriticaltemperatureofagasmaybe
definedasthattemperatureabovewhichitcannotbeliquefiednomatter
howgreatthepressureapplied.
Thecriticalpressure,P
c:Thecriticalpressuremaybedefinedasthe
minimumpressurerequiredtoliquefythegasatitscriticaltemperature.
TheCriticalVolume,V
c:TheCriticalVolumemaybedefinedas
thevolumeoccupiedbyamoleofthegasatthecriticaltemperature
andcriticalpressure.

9. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Atcriticaltemperatureandcriticalpressure,thegas
becomesidenticalwithitsliquidandissaidtobeincriticalstate.
Thesmoothmergingofthegaswithitsliquidisreferredto
astheCriticalPhenomenon.

10. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Methods of liquefaction of gases
Ifagasiscooledbelowitscriticaltemperatureandthensubjectedto
adequatepressure,itliquefies.
The3importantmethodsare:
1.Faraday’smethod
2.Linde’smethod
3.Claude’smethod

11. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
•Faraday(1823)usedfreezingmixturesoficewithvarioussalts
forexternalcoolingofgases.
•ApparatusconsistofV-shapedtubeinonearmofwhichthegas
wasprepared.Intheotherarm,thegaswasliquefiedunderits
ownpressure.
Faraday’s Method

12. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Themeltingofice&dissolutionofsaltsbothare
endothermicprocesses.Thetemperatureofthemixtureis
lowereduptoatemperaturewhenthesolutionbecomes
saturated.
Principle
Application
LiquefactionofgasessuchasSO
2,CO
2,NO
2andCl.
Limitation
The gases having low critical points could not be liquefied by
Faraday’s method. E.g.H
2, N
2and O
2

13. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Linde’sMethod
Linde(1895)usedJouleThomsoneffectasthebasisforthe
liquefactionofgases.
“Whenacompressedgasisallowedtoexpandintovacuum
oraregionoflowpressure,itproducesintensecooling.”
Inacompressedgasthemoleculesareverycloseandthe
attractionsbetweenthemareappreciable.Asthegasexpands,the
moleculesmoveapart.Indoingso,theintermolecularattraction
mustbeovercome.Theenergyforitistakenfromthegasitself
whichistherebycooled.
Principle

14. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Apparatus

15. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Puredryairiscompressedtoabout200atmospheresanditispassedthrough
apipecooledbyarefrigeratingliquidsuchasammonia.
Here,theheatofcompressionisremoved.Thecompressedairisthenpassed
intoaspiralpipewithajetatthelowerend.
Thefreeexpansionofairatthejetresultsinaconsiderabledropof
temperature.
Thecooledairwhichisnowataboutoneatmospherepressurepassedupthe
expansionchamber.
Itfurthercoolstheincomingairofthespiraltubeandreturnstothe
compressor.
Byrepeatingtheprocessofcompressionandexpansion,atemperaturelow
enoughtoliquefyairisreached.
Theliquefiedaircollectsatthebottomoftheexpansionchamber.
Working

16. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Claude’s Method
Thismethodforliquefactionofgasesismoreefficientthanthatof
Linde.
Herealsothecoolingisproducedbyfreeexpansionofcompressed
gas.Butinaddition,thegasismadetodoworkbydrivingan
engine.
Theenergyforitcomesfromthegasitselfwhichcools.
Thus,inClaude’smethodthegasiscoolednotonlybyovercoming
theintermolecularforcesbutalsobyperformanceofwork.
Principle

17. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Apparatus

18. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Puredryairiscompressedtoabout200atmospheres.Itisledthroughatube
cooledbyrefrigeratingliquidtoremoveanyheatproducedduringthe
compression.
Thetubecarryingthecompressedairthenentersthe‘expansionchamber’.
Thetubebifurcatesandapartoftheairpassesthroughtheside-tubeintothe
cylinderofanengine.Hereitexpandsandpushesbackthepiston.
Thustheairdoesmechanicalworkwherebyitcools.
Theairthenenterstheexpansionchamberandcoolstheincomingcompressed
airthroughthespiraltube.
Theairundergoesfurthercoolingbyexpansionatthejetandliquefies.
Thegasescapingliquefactiongoesbacktothecompressorandthewhole
processisrepeatedoverandoveragain.
Working

19. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Latentheat
Energyabsorbedorreleasedbyasubstanceduringachangein
itsphysicalstate(phase)thatoccurswithoutchangingitstemperature.
Thelatentheatassociatedwithmeltingasolidorfreezinga
liquidiscalledtheheatoffusion;
Thelatentheatassociatedwithvaporizingaliquidorasolidor
condensingavapouriscalledtheheatofvaporization.
Thelatentheatisnormallyexpressedastheamountofheat(inunits
ofjoulesorcalories)permoleorunitmassofthesubstance
undergoingachangeofstate.

20. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Forexample,
whenapotofwateriskeptboiling,thetemperatureremainsat100
°C(212°F)untilthelastdropevaporates,becausealltheheatbeing
addedtotheliquidisabsorbedaslatentheatofvaporizationand
carriedawaybytheescapingvapourmolecules.
Similarly,whileicemelts,itremainsat0°C(32°F),andtheliquid
waterthatisformedwiththelatentheatoffusionisalsoat0°C.
Theheatoffusionforwaterat0°Cisapproximately334joules
(79.7calories)pergram,andtheheatofvaporizationat100°Cis
about2,230joules(533calories)pergram.
Becausetheheatofvaporizationissolarge,steamcarriesagreat
dealofthermalenergythatisreleasedwhenitcondenses,making
wateranexcellentworkingfluidforheatengines.

21. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Vapourpressure
Whenaliquidisplacedinanopenvessel,itevaporates.The
moleculesintheliquidaremovingwithdifferentkineticenergies.
Themoleculesthatpossessaboveaveragekineticenergiescan
overcometheintermolecularforcesthatholdthemintheliquid.
Theseenergeticmoleculesescapefromtheliquidsurfaceas
vapour.
Theprocessbywhichmoleculesofaliquidgointothegaseous
state(vapors)iscalledVaporisationorEvaporation.
Thereverseprocesswherebygasmoleculesbecomeliquid
moleculesiscalledCondensation.

22. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Iftheliquidisplacedinaclosedvessel,themoleculeswithhigh
kineticenergiesescapeintospaceabovetheliquid.
Asthenumberofmoleculesinthegasphaseincreases,someofthem
striketheliquidsurfaceandgetcondensed.

23. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Astagecomeswhenthenumberofmoleculesescapingfromtheliquid
isequaltothenumberofmoleculesreturningtotheliquid.
Inotherwords,therateofevaporationexactlyequalstherateof
condensation.
Thusadynamicequilibriumisestablishedbetweentheliquidandthe
vapouratthegiventemperature.
Liquid ⇋Vapour
Nowtheconcentrationofthevapourinthespaceabovetheliquidwill
remainunchangedwithlapseoftime.Hencethevapourwillexerta
definitepressureattheequilibrium.
Thevapourpressureofaliquidisdefinedas:thepressureexertedbythe
vapourinequilibriumwiththeliquidatafixedtemperature.

24. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
EffectofTemperatureonVapourPressure
Ifthetemperatureoftheliquidisincreased,thevapourpressurewill
increasebecause,athighertemperaturemoremoleculesintheliquid
willhavelargerkineticenergyandwillbreakawayfromtheliquid
surface.
Also,athighertemperature,theaveragekineticenergyofthevapour
moleculeswillincrease.Bothvapourconcentrationandkinetic
energyareproportionaltotemperature.
Therefore,anyincreaseoftemperature
willresultintheincreaseofvapour
pressure.

25. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
DeterminationofVapourPressure
Thevapourpressureofagivenliquidcanbemeasuredby
1.Staticmethodor
2.Dynamicmethod.
1.TheStaticMethod

26. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Asufficientamountoftheliquidwhosevapourpressureistobe
determinedisplacedinthebulbconnectedtoamercurymanometer
andavacuumpump.
Alltheairfromthebulbisremovedbyworkingthevacuumpumpand
thestopcockclosed.
Apartoftheliquidevaporates.Thesystemisthenmaintainedata
fixedtemperatureforenoughtimesothattheequilibriumis
established.
Thedifferenceinthelevelsofmercuryinthemanometeris
equaltothevapourpressureoftheliquid.
Thismethodisusedforliquidshavingvapourpressuresuptoone
atmosphere.

27. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
2.The Dynamic Method

28. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Aninertgasispassedthroughthegivenliquidataconstant
temperature(T).
Thegassaturatedwiththevapouroftheliquidleavestheflaskatthe
exittube.
IfVbethevolumeofthegaspassedandmthelossinweightofthe
liquid,thevapourpressureisgivenbytheexpression
Vapourpressure=
??????
????????????
×????????????
Where,
M=molecularweightoftheliquidand
R=gasconstant.
Thismethodisparticularlysuitedforliquidsofverylowvapour
pressure.

29. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
General Characteristics of Gases
1.Expansibility
2.Compressibility
3.Diffusibility
4.Pressure
5.Effect of Heat
Gases

30. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Four parameters
1.Volume, Vof The Gas
2.Pressure, P
3.Temperature, T
4.Number of Moles, nofGas
Parameters Of a Gas (measurable properties)

31. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
The volume of the container is the volume of the gas sample.
It is usually given in liter (l or L) or milliliters (mlor mL).
1 1itre (l) = 1000 ml and 1 ml = 10
-3
l
One ml is practically equal to one cubic centimeter (cc).
Actually 1 liter (l) = 1000.028 cc
The SI unit for volume is cubic meter (m
3
)
The Volume, V

32. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Thepressureofagasisdefinedastheforceexertedbythe
impactsofitsmoleculesperunitsurfaceareaincontact.
Thepressureofagassamplecanbemeasuredwiththehelpofa
mercurymanometer.
Similarly,theatmosphericpressurecanbedeterminedwithamercury
barometer.
The pressure, p

33. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Thepressureofairthatcansupport760mmHgcolumnatsealevel,
iscalledoneatmosphere(1atm).
Theunitofpressure,millimeterofmercury,isalsocalledtorr
Thus,1atm=760mmHg=760torr
TheSIunitofpressureisthePascal(Pa).
TherelationbetweenAtmosphere,TorrandPascalis:
1atm=760torr=1.013×10
5
Pa
Theunitofpressure‘Pascal’isnotincommonuse.

34. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
ThetemperatureofagasmaybemeasuredinCentigrade
degrees(°C)orCelsiusdegrees.
TheSIunitoftemperatureisKelvin(K)orAbsolutedegree.
Thecentigradedegreescanbeconvertedtokelvinsbyusingthe
equation.
K=°C+273
TheKelvintemperature(orabsolutetemperature)isalwaysused
incalculationsofotherparametersofgases.
Thedegreesign(°)isnotusedwithK.
Temperature, T

35. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Thenumberofmolesn,ofasampleofagasinacontainercanbe
foundbydividingthemass,m,ofthesamplebythemolarmass,M
(molecularmass).
The Moles of a Gas Sample, n
moles of gas (n) =
mass of gas sample (m)
molecular mass of gas (M)

36. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
1.Boyle’s Law
“Atconstanttemperature,thevolumeofafixedmass
ofgasisinverselyproportionaltoitspressure.Ifthepressure
isdoubled,thevolumeishalved.”
Simple Gas Laws

37. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
TheBoyle’sLawmaybeexpressedmathematicallyas
V∝1/P (T,nareconstant)
orV=k×1/P
wherekisaproportionalityconstant.
PV=k
IfP
1,V
1aretheinitialpressureandvolumeofagivensampleofgas
andP
2,V
2thechangedpressure&Volume,wecanwrite
P
1V
1=k=P
2V
2
P
1V
1=P
2V
2

38. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Graphical representation of Boyle's law.

39. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
2.Charles’s Law
“Atconstantpressure,thevolumeofafixedmassofgasis
directlyproportionaltotheKelvintemperature.Iftheabsolute
temperatureisdoubled,thevolumeisdoubled.”

40. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Charles’ Law may be expressed mathematically as
V ∝T (P, n are constant)
or V = k T
where k is a constant.
or V/T = k
If V
1, T
1 are the initial volume and temperature of a given mass
of gas at constant pressure and V
2, T
2be the new values, we can
write
or

41. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
3.Avogadro’s Law
“Equalvolumesofgasesatthesametemperatureand
pressurecontainequalnumberofmolesormolecules.Ifthe
molaramountisdoubled,thevolumeisdoubled.”

42. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Lawmaybeexpressedmathematicallyas
V∝n (TandPconstant)
orV=An
whereAisconstantofproportionality.
orV/n=A
ForanytwogaseswithvolumesV
1,V
2andmolesn
1,n
2at
constantTandP,

43. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
The Ideal Gas Equation
We have studied three simple gas laws :
Boyle’s Law V ∝1/P
Charles’ Law V ∝T
Avogadro’s Law V ∝n
These three laws can be combined into a single more general gas law :
This is called the Universal Gas Law.
“Thevolumeofagivenamountofgasisdirectlyproportionaltothe
Numberofmolesofgas,directlyproportionaltothetemperature,andinversely
proportionaltothepressure.”
ItisalsocalledIdealGasLawasitappliestoallgaseswhichexhibitideal
behaviouri.e.,obeythegaslawsperfectly.

44. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Introducing the proportionality constant Rwe can write
or P V = nRT
The equation (2) is called the Ideal-gas Equation or simply thegeneral
Gas Equation. The constant Ris called the Gas constant.
For one mole (n = 1) of a gas, the ideal-gas equation is reduced to
PV = RT
…………….(1)
…………….(2)

45. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Kinetic Molecular Theory Of Gases
MaxwellandBoltzmann(1859)developedatheoryto
explainthebehaviourofgasesandthegaslaws.
Itisbasedonthefundamentalconceptthatagasis
madeofalargenumberofmoleculesinperpetual
motion.
Hencethetheoryiscalledthekineticmoleculartheory
orsimplythekinetictheoryofgases.

46. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Assumptions of the Kinetic Molecular Theory
Agasconsistsofextremely
smalldiscreteparticlescalled
moleculesdispersedthroughout
thecontainer.
(1)

47. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Theactualvolumeofthemoleculesisnegligible
comparedtothetotalvolumeofthegas.
(2)

48. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Gasmoleculesareinconstantrandommotionwithhighvelocities.
Theymoveinstraightlineswithuniformvelocityandchange
directiononcollisionwithothermoleculesorthewallsofthe
container.
(3)

49. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Thedistancebetweenthemoleculesareverylargeanditisassumed
thatvanderWaalsattractiveforcesbetweenthemdonotexist.Thus
thegasmoleculescanmovefreely,independentofeachother.
(4)
Allcollisionsareperfectlyelastic.Hence,thereisnolossofthe
kineticenergyofamoleculeduringacollision.
(5)
Thepressureofagasiscausedbythehitsrecordedbymoleculeson
thewallsofthecontainer.
(6)
Theaveragekineticenergy(½mv
2
)ofthegasmoleculesisdirectly
proportionaltoKelvintemperature.Thisimpliesthattheaverage
kineticenergyofmoleculesisthesameatagiventemperature.
(7)

50. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Ideal Gas & Real Gases
“Agasthatconfirmstotheassumptionsofthekinetictheoryofgasesis
calledanidealgas.”
Itobeysthebasiclawsstrictlyunderallconditionsoftemperature
andpressure.
“Therealgasesopposedtheassumptionsofthekinetictheoryofgases.”
e.g.hydrogen,oxygen,nitrogenetc.,areopposedtotheassumptions
a)Theactualvolumeofmoleculesinanidealgasisnegligible,whileinareal
gasitisappreciable.
b)Therearenoattractiveforcesbetweenmoleculesinanidealgaswhilethese
existinarealgas.
c)Molecularcollisionsinanidealgasareperfectlyelasticwhileitisnotsoin
arealgas.

51. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Deviations From Ideal Behaviour
Anidealgasisonewhichobeysthegaslawsorthegasequation
PV=RTatallpressuresandtemperatures.
Howevernogasisideal.
Almostallgasesshowsignificantdeviationsfromtheideal
behaviour.
ThusthegasesH
2,N
2andCO
2whichfailtoobeytheideal-gas
equationaretermednon-idealorrealgases.

52. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Compressibility Factor
“Theextenttowhicharealgasdepartsfromtheideal
behaviourmayberepresentedintermsofanewfunctioncalledthe
Compressibilityfactor”denotedbyZ
Z = PV/RT
Foranidealgas,Z=1anditisindependentoftemperatureand
pressure.
Thedeviationsfromidealbehaviourofarealgaswillbe
determinedbythevalueofZbeinggreaterorlessthan1.
Forarealgas,thedeviationsfromidealbehaviourdependon
PressureandTemperature.

53. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Effect of Pressure Variation on Deviations

54. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Effect of Temperature on Deviations
Fig shows plots of Z or PV/RT against P for N
2at different temperatures.

55. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Conclusions
1.Atlowpressuresandfairlyhightemperatures,realgases
shownearlyidealbehaviourandtheideal-gasequationis
obeyed.
2.Atlowtemperaturesandsufficientlyhighpressures,areal
gasdeviatessignificantlyfromidealityandtheideal-gas
equationisnolongervalid.
3.Thecloserthegasistotheliquefactionpoint,thelargerwill
bethedeviationfromtheidealbehaviour.

56. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
PHARMACEUTICAL AEROSOLS

57. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
“Asystemthatdependsonthepowerofacompressedor
liquefiedgastoexpelthecontentsfromthecontainer.”
“Pressurizeddosageformscontainingoneormoreactive
ingredientswhichuponactuationemitafinedispersionof
liquidand/orsolidmaterialsinagaseousmedium.”
Definition

58. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Advantages
Removal of dose without contamination.
Directly delivered to the affected area in a desired form.
Minimized manual contact with drug.
Rapid response.
Convenient, easy.
Controlled and uniform dosage by metered valves.
No manual contact with patient.

59. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Disadvantages
oCostly.
oDifficulty in disposal.
oDifficulty in formulation.
oQ.C testing is complicated.
oCannot be subjected to heat.

60. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Components
Aerosols consist of
1.Propellants
2.Container
3.Valve and actuator
4.Product concentrate
API
Additives
Suspending agent,
Antioxidant,
Emulsifying agents
Solvents
Aqueous
Nonaqueous

61. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Propellants
Responsiblefordevelopingproperpressurewithinthecontainer.
Providedrivingforcetoexpeltheproductfromthecontainer.
Types of Propellants
1.Liquefied gases Propellant
2.Compressed gases Propellants

62. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Liquefiedpropellantsaregasesthatexistasliquidsunder
pressure.
Becausetheaerosolisunderpressurepropellantexistsmainlyas
aliquid,butitwillalsobeintheheadspaceasagas.
Astheproductisusedupandthevalveisopened,someofthe
liquidpropellantturnstogas.
Liquefied Gases Propellants
1.Hydrocarbons (HC)
2.Chlorofluorocarbon (CFC)
3.Fluorinatedhydrocarbon(FHC)

63. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Hydrocarbons
It Can be used for water based aerosols for topical use.
Advantages
Inexpensive
Excellent solvents
It does not cause ozone depletion
Disadvantages
Inflammable
Unknown toxicity produced
Ex:
Propane -PropellantA-108
Isobutene -PropellantA-31
Butane -PropellantA-17

64. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Advantages
•Chemical inertness
•Lack of toxicity
•Non flammability.
•Lack of explosiveness.
Propellant of choice for oral and inhalation .
Disadvantages
•High cost
•It depletes the ozone layer
Examples:
Trichloro-monofluoro-methane -Propellant 11
Dichloro-difluoro-methane -Propellant 12
Dichloro-tetrafluoro-ethane -Propellant 114
Chloro Fluoro Carbons

65. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Examples:
Hydrofluoro Carbons & Hydro Chlorofluoro Carbons
Heptafluoro-propane -(HFA-227)
Tetrafluoro-ethane -(HFA-134a)
Difluoro-ethane -Propellant152a
Chloro-difluoro-methane -Propellant22
Chloro-difluoro-ethane -Propellant142b
Thesecompoundsbreakdownintheatmosphereatfasterratethan
CFCs.AndhavingLowerozonedestroyingeffect.
Advantages
•Low inhalation toxicity
•High chemical stability
•High purity
•Not ozone depleting
Disadvantages
•Poor solvent
•High cost

66. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Compressed Gas Propellants
Compressedgaspropellantsoccupytheheadspaceabovethe
liquidinthecan.
Whentheaerosolvalveisopenedthegas'pushes'theliquidout
ofthecan.
Theamountofgasintheheadspaceremainsthesamebutithas
morespace,andasaresultthepressurewilldropduringthelife
ofthecan.
Sprayperformanceismaintainedhoweverbycarefulchoiceof
theaerosolvalveandactuator.
Examples: Carbon dioxide, Nitrous oxide and Nitrogen

67. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
InAerosol,liquefiedgaspropellant/propellantmixtureandproduct
concentrateissealedwithinanaerosolcontainer,equilibriumisquickly
establishedbetweentheportionofpropellantthatremainsliquefiedand
thatpropellantwhichvaporizesandoccupiestheupperportionofthe
aerosolcontainer.
So,thevaporphasewhichdevelopspressureincontainer,againstthe
wallsofthecontainer.atvalveassemblyandthesurfaceoftheliquid
phase.
Onactuationtheaerosolvalveassemblyisactivated.
Uponactivationofthevalvethepressureexertedbythepropellantforces
thecontentsofthepackagetooutsidethroughtheopeningoftheaerosol
valve.
Principle / Mechanism & working of Aerosols

68. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Asthepropellantreleasedintotheair,itexpandsandevaporates
becauseofthedropdowninpressureandformliquiddropletsordry
particlesdependingupontheformulationtype.
Afterreleaseofsomeportionoftheliquidphaseequilibriumbetween
theremainingcontentsandthevapourstateisreestablished.
Soevenduringexpulsionoftheproductfromtheaerosolthepressure
withinthecontainerremainsconstantandtheproductmaybe
continuouslyreleasedatsamerateandwiththesameproportion.
Whentheliquidiscompletelyremoved,thepressurecannotbe
maintained,andthegasmaybeexpelledfromthecontainerwith
diminishingpressureuntilitisexhausted.

69. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa

70. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Container
Theymustbeabletowithstandpressuresashighas140to180psig
(poundspersq.inchgauge)at130°F.
Aerosol Container
A . Metals
1.Tinplated steel
2.Aluminum
3.Stainless steel
B. Glass
1.Uncoated glass
2.Plastic coated glass

71. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Valves
1.Continuous spray valve
2.Metering valves
Types of valves :
Capableofdeliveringthecontentinthedesiredformsuchas
spray,foam,solidstreametc.
Itcandeliveragivenamountofmedicament.

72. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Continuous spray valve
Used for topical aerosols .
Valves assembly consists :

73. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Components Made up of Uses
Mounting cup
Tin plated steel,
Al , brass
To attach valve to container.
Housing Nylon or derlin
Tosupport Stem, Gasket,
Spring
Stem
Nylon or derlin ,
brass & stainless steel
Controlthe flow
Gasket
Buna-n and neoprene
rubber
To seal Valve & Can
Spring Stainless steel To hold gasket in place
Dip tube
Poly ethylene
poly propylene
To draw product

74. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Metering Valves
Usedfordispensingofpotentmedication.
Operatesontheprincipleofachamberwhosesizedeterminesthe
amountofmedicationdispensed.
Approximately50to150mg±10%ofliquidmaterialscanbe
dispensedatonetimewiththeuseofsuchvalve.
MDI

75. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Actuators
Thesearespeciallydesignedbuttonswhichhelpsindeliveringthe
drugindesiredformi.e.,spray,wetstream,foamorsolidstream.
Types of actuators :
Spray actuators
Foam actuators
Solid steam actuators
Special actuators

76. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Classification of Aerosols
Aerosols may be classified as
1) Space Sprays
2) Surface coats
3) Foam

77. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
1.SpaceSprays:Thesearefinelydividedsprayshavingparticle
sizeupto50um.E.g.Insecticides,DisinfectantsandRoom
Deodorantsetc.
2.SurfaceCoats:Thesearealsospraysbutdispersephase
particlesarecoarsewithsizesupto200um.Theyproduceawet
coatwhensprayedonasurface.E.g.Hairsprays,Powdersprays
andtopicalmedicamentsprays.
3.Foam:Theseareproducedbyrapidexpansionofpropellants
throughanemulsion.Henceproductcomesoutintheformofa
foamorfroth.E.g.Shavingcream

78. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Types of aerosol systems
1.Solution system
2.Water based system
3.Suspension or Dispersion systems
4.Foam systems
a.Aqueous stable foams
b.Non aqueous stable foams
c.Quick-breaking foams
d.Thermal foams
5.Inhalers

79. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Solution system / 2 Phase system:
(Vapour + Liquid phase)
SolutionAerosolsaretwophasesystemsconsistingoftheproduct
concentrateinapropellantormixtureofpropellantsoramixtureof
propellantandsolvent.
Solutionaerosolscanbedifficulttoformulatebecausemany
propellantorpropellant-solventmixturesarenonpolarinnatureand
thesearepoorsolventsfortheaerosolproductconcentrate.
Solventsused
Ethylalcohol(mostcommonlyusedsolvent)
dipropyleneglycol
propyleneglycol
ethylacetate
acetone

80. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Footprotectivepreparations
Localanesthetics
Anti-inflammatorypreparations
Sprayfororalandnasalapplications.
Application
Contain;
50to90%propellantfortopicalaerosols.
upto99.5%propellantfororalandnasalaerosols.
Formulation

81. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Water based system / 3 components system : (Propellant +
Water + Vapour phase)
Largeamountofwatercanbeusedtoreplaceallorpartofthenon
aqueoussolventsusedinaerosols.
Thissystemiscomposedofalayerofwaterimmiscibleliquid
propellant,highlyaqueousproductconcentrateandthevapourphase.
Thistypeofsystememployedwhentheproductisimmisciblewiththe
propellant.
Duetoimmiscibilityofthewaterandpropellant,itformsathreephase
aerosol.
Ethanolusedasacosolventtosolubilizepropellantinthewater.
Thissystememitsthecontentsassprayorfoam.

82. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Suspension Aerosols
SuspensionAerosolscanprepare,whentheproduct
concentrateisinsolubleinthepropellantormixtureof
propellantandsolventorwhenaco-solventisnotdesirable.
Whenthevalveisopenedoractuated,thesuspension
formulationisemittedtoatmosphereandthepropellantrapidly
getsvaporizesandleavesafinedispersionoftheproduct
concentrate.
E.g:Anti-asthmaticdrugs,steroidsandantibioticsareprepared
insuspensionaerosols.

83. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Foam system / Emulsion systems
EmulsionorfoamaerosolsconsistofActiveingredient+
AqueousorNonaqueousvehicle+Surfactant+andpropellant
(Hydrocarbonorcompressedgases).
Herethepropellantwhichispresentintheliquidactsas
internalphase.
Theseaerosolsdispensedasstableaqueousornonaqueousor
quickbreakingfoamaerosol.

84. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Inhalers
Aninhaler(pufferorpump)isamedicaldeviceusedfor
deliveringmedicationintothebodyviathelungsandismainly
usedinthetreatmentofasthmaandchronicobstructive
pulmonarydisease.
Aerosolinhalationsaresolutions,suspensionsoremulsions
ofdrugsinamixtureofinertpropellantsheldunder
pressureinanaerosoldispenser.

85. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Metered Dose Inhalers

86. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Metered Dose Inhalers
MDIisthetypeofinhalerwhichonactivation,releasesa
fixeddoseofmedicationinaerosolform.
Usedtominimizethenumberofadministrationerrors.
Toimprovethedrugdeliveryofaerosolizedparticlesintothe
nasalpassagewaysandrespiratorytract.

87. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
AdvantagesofMDI:
Itdeliversspecifiedamountofdose.
Portableandcompact.
Quicktouse,
nocontaminationofproduct.
Dose-dosereproducibilityishigh.
DisadvantagesofMDI:
Lowlungdeposition;highpharyngealdeposition.
CoordinationofMDIactuationandpatientinhalationis
needed.

88. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Marketed Pharmaceutical Aerosol Products
Metered Dose inhalers
BrandName Drug Use
FloventDiskus Fluticasone Asthma
Advair Fluticasoneand SalmeterolAsthma
Aerobid Flunisolide Asthma
Qvar Beclomethasone Asthma
Proventil Albuterol Bronchospasm

89. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
LiquidCrystals
Thereisastateofmatter,whichdoesnotmeetthenecessary
requirementsofanyofthree(solid,liquid,andgas)categories.
Forexample,
Asubstancelikecholesterolormayonnaiseissomewhere
betweenaliquidandasolid.
Thisisnotquiteliquidorquitesolid,butisaphaseofmatterwhose
orderisintermediatebetweenthatofaliquidandcrystal.
Itisoftencalledamesomorphicstate,whichisstateofmatter
inwhichthedegreeofmolecularorderisintermediatebetweenthe
perfectthreedimensional,long-rangepositionalandorientational
orderfoundinsolidcrystalsandtheabsenceoflong-rangeorder
foundinliquids,gases,and-amorphoussolids.
Itisalsocalledasmesointermediate.

90. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Physically,theyareobservedtoflowlikeliquidsshowingsome
propertiesofcrystallinesolids.
Hencethisstateisconsideredtobethenextstateofmatterknownas
liquidcrystal(LC)state.
TheLCstateisalsoknownasmesophaseandcanbedefinedas
thecondensedmatterthatexhibitintermediatethermodynamicphase
betweenthecrystallinesolidandsimpleliquidstate.
LCscanbeconsideredtobecrystals,whichhavelostsomeorallof
theirpositionalorderwhilemaintainingfullorientationalorder.
Theyarefreetomove,butliketolineupinaboutthesamedirection.
ThedegreeofmobilityofthemoleculesintheLC'sislessthanthatof
aliquid.

91. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
State Characteristics
Crystallinesolids
Exhibitshortaswellaslong-rangeorderwithregardto
bothpositionandorientationofthemolecules.
Liquids
Amorphousingeneral.
Butmayshowshort-rangeorderwithregardtoposition
and/ororientation,
Liquidcrystals
Showatleastorientationallong-rangeorderandmayshow
short-rangeorder,whereaspositionallongrangeorder
disappears.

92. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Theliquidcrystalsareofthermotropicandlyotropictypes.
Lyotropicliquidcrystals:areinducedbythepresenceofsolvent.
Thermotropicliquidcrystals:areinducedbyachangeintemperatureand
areessentiallyfreeofsolvent.
Whentransitionbetweenthephasesistemperaturedependent,asshownin
Fig.,theyarecalledthermotropic
whentransitionsaredependentofdifferentcomponentstheseLC'sarecalled
lyotropic.
Thermotropicsaremostlyusedintechnicalapplications,whilelytropicsare
importantforbiologicalsystemssuchasmembranes.

93. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
TherearethreetypesofliquidcrystalsasshowninFig.
TypesofLiquidCrystals:
1.NematicCrystal
2.Smecticliquidcrystals
3.Cholestericcrystal

94. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
NematicCrystal
Inthesimpleliquidcrystallinestatethemoleculespossessonly
orientationalbutnopositionalorderarecallednematiccrystal
phase.Inthenematicphasethemoleculescanrotateaboutoneaxis
(I.e.Uniaxial)andaremobileinthreedirections.
Theyarepolarizablethreador
rodlikeorganicmoleculeson
theorderof25inlengthsand
5inheight,.Theorderof
nematiccrystalisafunctionof
temperature.

95. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Aunitvectorcallednematicdirectorcandescribethedirectionof
consideredalignment.
Asnematicsarecharacterizedbyorientationalorderoftheconstituent
molecules,themolecularorientationandhencethematerial'soptical
properties,canbecontrolledwithappliedelectricfields.
Nematicsarethemostcommonlyusedphaseinliquidcrystaldisplayswith
manysuchdevicesusingthetwistednematicgeometry.Theschematic
presentationoftwistednematiccrystalphaseisshowninFig.

96. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Smecticliquid
Smecticliquidcrystalsarecharacterizedbyonemoreadditionaldegree
ofpositionalorderthannematicsthatthemoleculescanonlyrotate
aroundoneaxisandmobileinonlytwodirections,(e.g.P-
ozoxyanisole.)
Cholestericcrystal
LCswhenmadeofasymmetricmoleculesthatdifferfromtheirmirror
imageacholestericliquidcrystale.g.cholesterolacetate,isobtained.
Cholestericcanbesimilartonematics,butdifferintheconsidered
orientationthatitformsahelicalstructurewiththehelicalaxis
perpencliculartothedirector.

97. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
PhysicalProperties:
Physicalpropertiesofliquidcrystalsareanisotropicdueto
orientationalorder.
Thesepropertiesaretheheatofdiffusion,themagnetic
susceptibility,thedielectricpermittivityortheoptical
properties.
Liquidcrystalsaresensitivetoelectricalfields,aproperty
thathasbeenusedindisplaysystems.
Liquidcrystalsaremobileandfoundtoshowflowproperties
ofliquidslikerotationalviscosityactingondynamic
directordeformations.

98. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Applications
Theyarebestknownfortheirapplicationindisplays.
liquidcrystalsarealsoanessentialpartofalllifeforms.
Lyotropicliquidcrystalsareessentialorganicsubstances,DNA,
lipidsofcellularmembranesandproteinsaresomeexamplesof
well-knownliquidcrystals.
TheLCstateiswidespreadinnaturesuchaslipoidalforms
foundinnerves,braintissueandbloodvessels.
LC'smayalsobeassociatedwitharthrosclerosisandformation
ofgallstones.
Theyarebelievedtohavestructuressimilartothoseofcell
membranes.

99. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
GlassyState
“Glassisanon-equilibrium,non-crystallinestateofmatter
thatappearssolidonashorttimescalebutcontinuouslyrelaxes
towardstheliquidstate.”
Glass,however,isactuallyneitheraliquid-supercooledor
otherwisenorasolid.
Itisanamorphoussolid;astatesomewherebetweenthosetwo
statesofmatter.
Andyetglass'sliquidlikepropertiesarenotenoughtoexplain
thethicker-bottomedwindows,becauseglassatomsmovetoo
slowlyforchangestobevisible.

100. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Whenglassismade,thematerial(oftencontainingsilica)isquickly
cooledfromitsliquidstatebutdoesnotsolidifywhenits
temperaturedropsbelowitsmeltingpoint.
Atthisstage,thematerialisasupercooledliquid,anintermediate
statebetweenliquidandglass.
Tobecomeanamorphoussolid,thematerialiscooledfurther,below
theglass-transitiontemperature.
Pastthispoint,themolecularmovementofthematerial'satomshas
slowedtonearlyastopandthematerialisnowaglass.
Thisnewstructureisnotasorganizedasacrystal,becauseitdidnot
freeze,butitismoreorganizedthanaliquid.

101. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Forpracticalpurposes,glassislikeadisorganizedsolid.
Likeliquids,thesedisorganizedsolidscanflow,althoughveryslowly.
Overlongperiodsoftime,themoleculesmakinguptheglassshift
themselvestosettleintoamorestable,crystallikeformation.
-Ediger
Glass–liquidtransition
Theglass–liquidtransition,orglasstransition,isthegradualand
reversibletransitioninamorphousmaterials(orinamorphousregions
withinsemi-crystallinematerials),fromahardandrelativelybrittle
"glassy"stateintoaviscousorrubberystateasthetemperatureis
increased.

102. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Types of Solids
1.Crystalline solids
2.Amorphous solids
The Solids

103. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Crystallinesolids
Acrystallinesolidexistsassmallcrystals,eachcrystalhavinga
characteristicgeometricalshape.
Inacrystal,theatoms,moleculesorionsarearrangedina
regular,repeatingthree-dimensionalpatterncalledtheCrystal
Lattice.
SugarandSodiumChloridesaltarecrystallinesolids.
CrystalLattice

104. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Amorphoussolid
Anamorphoussolid(amorphous=noform)hasatoms,molecules
orionsarrangedatrandomandlackstheorderedcrystallinelattice.
Examplesarerubber,plasticsandglass.

105. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa

106. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
1.Metalliccrystals:arecomposedofbondedmetalatoms;
Example:Na,Cu,Fe,andalloys.
2.Covalentcrystals:consistedofaninfinitenetworkofatomsheld
togetherbycovalentbonds,noindividualmoleculesbeingpresent.
Example:Diamond,Graphite
3.Molecularcrystals:arecomposedofindividualmolecules.
Example:Ar,Napthtalene
4.Ioniccrystals:consistedofpositiveandnegativeions;
Example:NaCl,MgO,CaCl
2andKNO
3
TypesofCrystallinesolids

107. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
ThehabitofaCrystal
Theexternalshapeiscalledthehabitofthecrystal.
Theplanesurfacesofthecrystalarecalledfaces.
Theanglesbetweenthefacesarereferredtoastheinterfacial
angles.
Thehabitofacrystalofagivencompounddependsontherateof
developmentofthedifferentfaces.
Slowgrowthfromaslightlysuper-saturatedsolutionoravery
slowlycoolingsolutiongiveslargecrystals.

108. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Inthepresenceofcertainimpurities,differentfacesgrowatdifferent
ratesandgiverisetomanyforms.
Example,
IfSodiumChlorideiscrystallisedfromitssupersaturated
solution,itformscubiccrystals.Butifureaisaddedasimpurity,
itgivesoctahedralcrystals.

109. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Differentcrystalsofthesamesubstancemaynotlookalike.
Buttheinterfacialanglesarealwaysthesame.

110. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Dependingonthearrangementoffaces,crystalhabitscandescribedin
deferentways
1)Plate:eachparticlesofsimilarlength&width.
E.g.Naphthalene
2)Tabular:flatparticlesofsimilarlength&widthbutpossessgreater
thicknessandflacks
E.g.Tolbutamide

111. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
3)Equant:particlesofsimilarlength,widthandheight
E.g.Sodiumchloride
4)Columnar:rodlikeparticleshavingwidthandthicknessexceeding
needletypeparticles.
E.g.Flurocortisoneacetate

112. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
5)Blade:longthinflatparticles.
E.g.Resorcinol
6)Acicular:needlelikeprisms.
E.g.Nalidixicacid

113. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Thesimplebasicunitorthebuildingblockofthecrystal
latticeiscalledtheUnitcell.
Crystal structure

114. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Parameters of the Unit Cells
Theunitcellsmaybecharacterizedbythefollowingparameters:
A.Relativelengthsoftheedgesalongthethreeaxes(a,b,c).
B.Thethreeanglesbetweentheedges(α,β,γ).

115. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
In1850,AugustBravais,(Frenchmathematician)observedthatthe
crystallatticeofsubstancesmaybecategorizedintoseventypes.These
arecalledBravaislattices.
�=�=�=90°
�=�=�
�=�=�=90°
�=�≠�

116. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
�=�=�≠90°
�=�=�
�=�=�=90°
�≠�≠�

117. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
�=�=90°
�=�≠�
�≠�≠�≠90°
�≠�≠�
�≠�≠�
�=�=90°�≠90°
�=120°

118. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
The Seven Unit Cells

119. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Polymorphism
“Theoccurrenceofthesamesubstanceinmorethanonecrystalline
formsisknownasPolymorphism.”
Thisphenomenonisshownbybothelementsandcompounds.
“IfanelementCrystallizesasmorethanonedistinctcrystalline
species,thisphenomenoniscalledasAllotropy”
Theindividualcrystallineformsofanelementarereferredtoas
polymorphsorallotropes.
Example:RhombicandMonoclinicSulphuraretwopolymorphsor
allotropesofSulphur.
Thepolymorphicorallotropicformsofanelementhavedistinct
physicalpropertiesandconstituteseparatephases.

120. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Allotropycanbedividedintothreetypes:
1.Enantiotropy,
2.Monotropy
3.Dynamicallotropy.

121. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Enantiotropy
Insomecasesonepolymorphicform(orallotrope)canchangeinto
anotheratadefinitetemperaturewhenthetwoformshavea
commonvapourpressure.Thistemperatureisknownasthe
transitiontemperature.
Oneformisstableabovethistemperatureandtheotherformbelow
it.
“InAllotropy,whentheelementgetchangedfromone
crystallineformtotheotheratthetransitiontemperatureis
reversible,thephenomenoniscalledenantiotropy.”

122. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Forexample,
Rhombicsulphur(??????-sulphur)onheatingchangestomonoclinic
sulphur(ß-sulphur)at95.6ºC(transitiontemperature).
Also,monoclinicsulphur,oncooling,againchangestorhombic
sulphurat95.6ºc.
Thatis,
95.6°C
??????-Sulphur ß-Sulphur

123. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Monotropy
Itoccurswhenoneformisstableandtheothermetastable.
Themetastablechangestothestableformatalltemperaturesand
thechangeisnotreversible.
Thusthereisnotransitiontemperatureasthevapourpressuresare
neverequal.
Itmaybedefinedasirreversiblechangeinallotropicformsof
crystalsbecauseofunequalvapourpressureandlackoftransition
temperature.
Example:Thistypeofpolymorphismisexhibitedbyphosphorus,
White phosphorus → Red phosphorus

124. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Dynamicallotropy
“FormofallotropyinwhichSomesubstanceshaveseveral
formswhichcancoexistinequilibriumoverarangeoftemperature
andareusuallyhavedifferentmolecularformulaebutthesame
empiricalformula,knownasdynamicallotropy.”
Theamountofeachisdeterminedbythetemperature.
Anexampleofdynamicallotropyisprovidedbyliquidsulphur
whichconsistsofthreeallotropesS
µ,S
pandS
λ.
S
µ S
p S
λ

125. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
PharmaceuticalApplicationsofPolymorphism
1.EnhancedSolubility
MetastableformshavelowMeltingpointsandhighsolubility.
Form M.P. ºc
Aq. Solubility
(mg/ml)
Riboflavin,Form I (Stable) 291 60
Riboflavin,Form II 278 80
Riboflavin,Form III 183 1200
2.Improveddissolution
Ifsolubilityisenhanced,theDissolutionratealsoincrease.
E.g.MetastablePolymorphofmethylprednisolone(FormII)has1.4
timeshigherrateofdissolutionthanStableform(FormI)

126. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
4.Manufactureofdosageforms
Theprincipleofpolymorphismisusedinmanufacturingofcocoa
buttersuppositories.
Form Stability M.P. ºc
Cocoa Butter,�Metastable 18
Cocoa Butter,�Metastable 22
Cocoa Butter,�’ Metastable 28
Cocoa Butter,�Stable 34.5
3.EnhancedAbsorption
Asthesolubility&Dissolutionareenhanced,theAbsorptionrate
alsoincrease.
E.g.MetastablePolymorphofmethylprednisolone(FormII)has1.7
timeshigherrateofAbsorptionthanStableform(FormI)

127. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
1.Colourchange
2.Densitychange
3.Solubilitychange
4.Coolingcurvemethod
Detection Techniques of Polymorphism

128. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Colourchange
Ifalittlemercury(II)iodideisplacedinameltingpointtube
attachedtoathermometerandheatedinsomeformofapparatus
(e.g.,electricalheater),itispossibletorecordtemperatureat
whichtheredmercury(II)iodidechangestotheyellowform.

129. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Densitychange
Asrhombicsulphurchangestomonoclinicsulphur,thereisa
decreaseindensityand,therefore,anincreaseinvolume.
Thechangeinvolumeisemployedtomeasurethetransition
temperaturebyusinganapparatusknownasDilatometer.

130. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Solubility change
Twoformsofthesamesubstancehavedifferentsolubilitiesbutat
thetransitionpointtheyhaveidenticalsolubility.
Thusifsolubility-temperaturegraphisplottedforthetwoforms,it
isfoundtoconsistoftwopartswithasharpbreak.
Whileonepartrepresentsthesolubilitycurveforoneform,the
secondpartrepresentsthatfortheother.
Atthemeetingpointofthetwocurves,thesolubilityofthetwo
formsisthesameanditindicatesthetransitiontemperature.

131. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Cooling curve method
SupposethatformAisconvertedintoform
Bonheating.NowletBisallowedtocool
andacurveobtainedbyplottingthe
temperatureagainstthetime.
Thecurvewillshowdistinctbreakata
temperaturecorrespondingtothetransition
pointbecausehereheatisevolvedfromB.
Thereisoftenanevolutionorabsorptionofheatwhenoneformpasses
totheother.
Thismethodissuitablefordeterminingthetransitiontemperature
betweendifferenthydratesofasaltorbetweenahydrateandan
anhydroussaltorfordifferentformsofametal.
e.g.Na
2SO
4.10H
2OchangestoNa
2SO
4

132. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Psedomorphism
“Pseudomorphsaredefinedasthosesolidforms,whicharise
becauseofinclusionofsmallamountofsolventofcrystallization.”
ThesearealsoknownasSolvates.
Whenwateristhesolventofcrystallization,thecrystalsare
termedasHydrates.
CrystalsthatdonotcontainwaterareknownasAnhydrate.
Example: Drug : Ampicillin
Pseudomorphs: Ampicillinmonohydrate.
Ampicillintrihydrate.

133. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
EutecticMixtures
Atwo-componentsysteminwhichthecomponentsare
completelymiscibleintheliquidstatesandarecompletely
immiscibleinthesolidstate.Thisisbecausethesolidphaseconsists
ofpurecomponent.Thismixtureisknownaseutecticmixture.
Thetemperatureatwhichsuchsystemexistsinliquidphaseis
knownaseutectictemperature.
Abovethistemperaturethecomponentsareliquidandbelowthis
temperaturetheyaresolids.
Physicallyeutecticsystemsaresoliddispersions.
Someexamplesofthistypearethymol-salol,thymol-camphor,
menthol-camphoretc.

134. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
InFig.themeltingtemperatureoftwosubstancesAandBareplottedagainst
mixturecompositions.
ThecurvesseparatingtheregionsofA+LiquidandB+Liquidfromregions
ofliquidABaretermedliquiduscurves.
ThehorizontallineseparatingthefieldsofA+LiquidandB+LiquidfromA
+Ballsolid,istermedthesolidus.

135. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
UponadditionofBtoAorAtoBtheirmeltingpointsarereduced.
ThepointE,wheretheliquiduscurvesandsolidusintersect,istermedthe
eutecticpoint.
Attheeutecticpointinthistwo-componentsystem,allthreephases,thatis
Liquid,crystalsofAandcrystalsofB,allexistinequilibrium.
Theeutecticpointrepresentsacomposition(eutecticmixturecomposition)at
whichanymixtureofAandBhasthelowestmeltingpoint.

136. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
IfwecoolsolutionofAandBwhichisricherinAthantheeutectic
mixture,thenthecrystalofpureAwillappear.
Asthesolutioniscooledfurther,moreandmoreofAgetcrystallizeout
andthesolutionbecomesricherinB.
Whentheeutecticpointisreached,theremainingsolutioncrystallizes
outformingamicrocrystallinemixtureofpureAandpureB.
Significance
Ifsalol-thymolcombinationsistobedispensedasdrypowder,itis
necessarythattheambienttemperatureshouldbebelowitseutectic
pointof130°C.
Abovethistemperature,itexistsinliquefiedform.Ateutecticpoint
theircontributionwithrespecttocompositionis34%thymoland66%
salol.

137. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Physicochemical Properties
1.Refractive index
2.Optical activity
3.Dipole moment
4.Dielectric constant
5.Dissociation constant

138. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Refractive index
Whenmonochromaticlightpassesthroughalessdensemedium(airor
vacuum)andentersadensermedium(glassorwater),theadvancingwaves
atinterfacearemodifiedandbroughtclosertogether.
Thisleadstodecreaseinspeedandshorteningofwavelength.

139. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Whenlightpassesthedensermedium,apartofwaveslows
downmorequicklyasitpassesthroughinterfaceandmakesitbend
towardsthenormal.Thisphenomenoniscalledasrefraction.
Theamountofbendingoflightwhenittravelfromrarertodenser
mediumcanbeexpressedasrefractiveindex(n).
Therefractiveindexisaquantitywhichisaconstantforapure
substanceunderstandardconditionsoftemperatureandpressure.
TheRIofasubstanceisstronglyinfluencedbytemperatureand
thewavelengthoflightusedtomeasureit.
Thisisusuallywritten
1n
2(refractiveindexofmaterial2withrespect
tomaterial1.

140. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Theratioofthespeedoflightinavacuumtothespeedoflight
inanothersubstanceisdefinedastheindexofrefractionforthe
substance.
n=indexofrefractiveindex=
speedoflightinavacuum
speedoflightinasubstance
or
Itistheratioofthesineoftheangleofincidenceofarayoflight
onthesurfaceseparatingtwomediatothesineofitsangleof
refraction.
n=indexofrefraction=
sini
sinr
Where
i=angleofincidence,
r=angleofrefraction
Refractiveindex

141. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Index of Refraction

142. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Measurement of RI
TheinstrumentusedtomeasureRIiscalledRefractrometer.
Variousrefractometerusedare;
1.Abberefractometer
2.Pulfrichrefractometer
3.Immersionrefractometer
Abbesrefractometeriscommonlyusedatlaboratoryscalebecause
ofitsadvantagesoverotherrefractometer.
Itismostconvenient,
Reliableandsimpleinstrument
Smallsamplesizerequired.
Easymaintenanceandeconomical.

143. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Application of RI
RIisanIntrinsicpropertyofsubstance.
Usedindeterminingpurity,identity.
Usedforanalysisofbinarymixture-glycerinwatermixture.
Determinationofsugarconcentration,alcoholcontentinfermentation.
Unsaturationinvegetablesoildeterminedbyspecificrefraction.
Molarrefractionusefulinstudyofmolecularstructure.

144. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Plane Polarized Light
Accordingtowavetheoryoflight,anordinaryraylightisconsideredtobe
vibratinginallplanesatrightangletothedirectionofpropagation.
Ifthisordinaryrayoflightispassedthroughapolarizer(NICOL
prism),theemergentrayhasitsvibrationonlyinoneplane.Thislighthaving
wavemotioninonlyoneplaneisknownasPlanePolarizedLight.
Optical activity

145. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Opticalactivityisuniquecharacterforamolecule.
Asubstanceissaidtobeopticallyactiveifitrotatestheplaneof
thepolarizedlight.
Thesubstanceshavingabilitytorotatetheplanepolarizedlight
towardsclock-wisearecalledDextrorotatory(+).
E.g.Dextrose
Thesubstanceshavingabilitytorotatetheplanepolarizedlight
towardsanti-clockwisedirectionarecalledLaevorotatory(-).
E.g.Laevulose

146. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Polarimetry:ThetermPolarimetrymaybereferredasthestudyofthe
rotationofpolarizedlightbytransparentopticallyactivesubstance.
Thismeasurestherotationofthepolarizedlightasitpassesthroughan
opticallyactivecompound.
Measurement of Optical activity
Thistechniqueinvolvesthe
measurementofchangein
thedirectionofvibration
ofpolarizedlightwhen
interactwithanoptically
activecompound.

147. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
TheRotatoryPowerofagivensolutionisgenerallyexpressedas
specificrotation.
Itisthenumberofdegreesofrotationofplanepolarized
lightproducedbyonegramofthesubstanceperml.
Themeasurementsiscarriedoutatconstanttempusingsodium
light.
TheSpecificrotationcanbeCalculatedbythefollowingrelation:
Specific rotation
??????
??????
??????
=
??????
??????×??????
[α]=specificrotation,
t=temperature,
λ=wavelength,
??????=opticalrotation,
c=concentrationing/100ml,
l=opticalpathlengthindm.

148. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Applications
IdentificationandDeterminationofOpticallyactivecompounds.
Opticalactivityistheonlyoneparameter,fordistinguishingbetweenD
&Lisomericforms.
InChemicalindustryManychemicalsexhibitaspecificrotationasa
uniquepropertywhichcanbeusedtodistinguishit.
InFood,beverageandpharmaceuticalindustries,specificrotationscanbe
calculatedforpurityandconcentrationforsubstancelikeSteroids,
Diuretics,Antibiotics,Narcotics,Vitamins,Analgesics,AminoAcids,
EssentialOils,Polymers,Starches,Sugars.
Opticalrotationisusedinthesugarindustryfordeterminingqualityof
bothjuicefromsugarcaneandtherefinedsucrose.
Polarimetryisusedinremotesensingapplications,suchasplanetary
scienceandweatherradar.

149. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
InamoleculesuchasHCl,thebondingelectronpairisnotshared
equallybetweenthehydrogenatomandthechlorineatom.
Thechlorineatomwithitsgreaterelectronegativity,pullsthe
electronpairclosertoit.
Thisgivesaslightpositivecharge(+q)tothehydrogenatomanda
slightnegativecharge(–q)tothechlorineatom.
Dipole moment

150. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Amoleculewithapositivechargeatoneendandanegative
chargeattheotherendisreferredtoasanelectricdipoleorsimply
dipole.
Thedegreeofpolarityofapolarmoleculeismeasuredbyitsdipole
moment,µ.
Thedipolemomentofapolarmoleculeisgivenbytheproduct
ofthechargeatoneendandthedistancebetweentheopposite
charges.
Thus,µ= q ×r

151. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Itisrepresentedbyanarrowwithacrossedtail.
Thearrowpointstothenegativechargeanditslengthindicatesthe
magnitudeofthedipolemoment.
ThusamoleculeofHClmayberepresentedas;

152. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Unit of Dipole Moment
TheCGSunitfordipolemomentistheDebye(D).
ADebyeisthemagnitudeofthedipolemoment(µ)whenthe
charge(q)is1×10
-10
esu(electrostaticunits)anddistance(r)is1Å
(10
-8
cm).
µ=q×r
=1×10
-10
×10
-8
=1×10
-18
esucm
Thus1D=1×10
-18
esucm
InSIsystem,thechargeisstatedinCoulombs(C)anddistancein
meters(m).ThusdipolemomentisexpressedinCoulombmeters
(Cm).
TherelationofDebyetoSIunitsisgivenbytheexpressioncoulomb:
1D=3.336×10
-30
Cm

153. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Determination of Dipole Moment
Electriccondenser.
Theparallelplatesofthecondensercanbechargedbyconnecting
themtoastoragebattery.
Whenthecondenserischarged,anelectricfieldissetupwithfield
strengthequaltotheappliedvoltage(V)dividedbythedistance(d)
betweentheplates.

154. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Polarmoleculesareelectricdipoles.Thenetchargeofadipoleis
zero.
Whenplacedbetweenthechargedplates,itwillneithermove
towardthepositiveplatenorthenegativeplate.
Ontheotherhand,itwillrotateandalignwithitsnegativeend
towardthepositiveplateandpositiveendtowardthenegative
plate.Thusallthepolarmoleculesalignthemselvesintheelectric
field.
Thisorientationofdipolesaffectstheelectricfieldbetweenthetwo
platesasthefieldduetothedipolesisopposedtothatduetothe
chargeontheplates.

155. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Procedure
Platesarechargedtovoltage,Vpriortointroductionofthepolar
substance.Thesearethendisconnectedfromthebattery.
Onintroducingthepolarsubstancebetweentheplates,thevoltage
willchangetovalueV’.
Dielectricconstantcanbecalculatedby;
??????=
??????
??????
′
ExperimentallydeterminedvalueofDielectricconstantcanbeused
tocalculatedipolemoment.

156. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Dipolemomentprovideusefulinformationaboutthegeometry
ofmolecularstructure.
UsefultostudyBondmoment.
Itisusedtodistinguishbetweencisandtransisomer.
Identificationofo,mandpisomers.
Usedtostudyioniccharacterofsomemolecules.
Application

157. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Thedielectricconstantofasolventmaybedefinedasitscapacity
toweakentheforceofattractionbetweentheelectricalcharges
immersedinthatsolvent.
Theseparationofchargecanbebestunderstoodfromtheconceptof
Dielectricconstant.
Dielectric constant
Theparallelplatesareseparatedbysome
mediumacrossadistancerandconnectedto
voltagesupplysource.
Theelectricitywillflowacrosstheplatesfrom
lefttorightthroughthebatteryuntilpotential
differenceoftheplatesequalsthatofthe
batterywhichissupplyingtheinitialpotential
difference.

158. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Thecapacitance,C,isequaltotheamountofelectriccharge,q,
storedontheplates,dividedbyV,thepotentialdifference,between
theplates.
Thecapacitanceofcondenserdependsonthethicknessofthe
condenserseparatingtheplates.
TheC
oisusedascapacitancereferencemediumonwhichto
compareothermediums.TheC
oisthecapacitancebetweenthe
plateswhenavacuumfillsthespacebetweentheplates.
Theratioofcapacitanceoftestmaterial(C
x)dividedbythe
capacitanceofreferencematerialistermedasdielectricconstant.
C=
q
V
??????=
??????
??????
??????
??????

159. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Thepolarityofthesolventdependsonthedielectricconstantas
moreisthepolarsolventgreateristhedielectricconstant.
Thereforedielectricconstantofasubstanceaffectsthesolubility
ofthatsubstance.
Thehigherthevalueofthedielectricconstantthegreateristhe
dissociationoftheelectrolytedissolvedinitbecausethe
electrostaticforcesvaryinverselyasthedielectricconstantof
themedium.
Water,whichhasahighvalueofdielectricconstantis,
therefore,astrongdissociatingsolvent.
Theelectrostaticforcesofattractionbetweentheionsare
considerablyweakenedwhenelectrolytesaredissolvedinit
andasaresult,theionsbegintomovefreelyandthereisan
increaseintheconductanceofthesolution.

160. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Dissociationoftheelectrolytedissolvedinsolventsisdepends
onDielectricconstantofthatsolvent.
SolubilityofelectrolytesiscorrelatedwithDielectricconstant.
Helpsinselectionofsolventsforvariousoperations.
UsedinIdentificationofvarioussolvents.
Application

161. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Whenacertainamountofelectrolyte(A
+
B
–
)isdissolvedinwater,a
smallfractionofitdissociatestoformions(A
+
andB
–
).
Whentheequilibriumhasbeenreachedbetweentheundissociated
andthefreeions,wehave
AB⇋A
+
+B
–
Thefractionoftheamountoftheelectrolyteinsolution
presentasfreeionsiscalledtheDegreeofdissociation.
Ifthedegreeofdissociationisrepresentedbyx,wecanwrite
??????=
amountdissociated(mol/L)
initialconcentration(mol/L)
Dissociation constant

162. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
ThevalueofxcanbecalculatedbyapplyingtheLawofMass
Actiontotheionicequilibriumforweakacid,say;
HA+H
2O⇋A
-
+H
3O
+
AccordingtotheLawofMassaction,therateofforwardreaction
(R
fisproportionaltotheconcentrationofreactantsandtherateof
reversereaction(R
b)isproportionaltotheconcentrationofproducts
R
f= K
1[HA][H
20]
R
b= K
2[A
-
][H
30
+
]
At equilibrium; R
f =R
b
Solving the ratio K
1/K
2we obtain
K=
??????
�
??????
�
=
A
−
H
30
+
HAH
20

163. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Since[H
20] is constant, equation may be written as;
KH
20=
A
−
H
30
+
HA
=??????
??????
where K
a=ionisation or dissociation constant of the weak acid
pKavalue refers to negative log of dissolution constant of the weak
acid.

164. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Determination of Dissociation constant
Thedissociationconstantforaweakacidorbasecanbeobtained
byvariousmethodssuchas
Conductivitymeasurements,
Visibleorultravioletabsorptionspectrometry,
Potentiometry,etc.
Ofthesemethods,potentiometricpHmeasurementisthemost
widelyused.

165. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
Theprincipleinvolvedinthismethodmaybeunderstoodby
referringtheequation;
whenequimolarconcentrationsofsalt[A
-
]andacid[HA]are
present,thedissociationconstantK
anumericallyisequaltothe
hydroniumionconcentration.
i.e.K
a=[H
30
+
]when[A
-
]=[HA]
FordeterminationofK
a;tomeasurethepHofasolutioncontaining
equimolarconcentrationsoftheacidandastrongbasesaltofthe
acid.AtthisconcentrationpH(whichisthenegativelogof[H
30
+
]is
equaltopKa.
FrompKatheK
amaybecalculated.
K
a=
A
−
H
30
+
HA
Principle of Potentiometry

166. By: Khalifa M Asif Y Asst. Professor Pharmaceutics Dept. AACOP Akkalkuwa
TodeterminedegreeofDissociationofvariousionicmolecules.
Helpsinselectionofsolventsforvariousoperations.
Usedinchemistrytostudyacidbasereaction.
Determinationofconcentrationofboundmolecules.
Studyofproteinligandbinding.
Application