Colloidal Disp[1]_ppt [Compatibility Mode]

7/31/2019 Colloidal Disp[1]_ppt [Compatibility Mode]

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COLLOI DS


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Collo id a l Disp e r s ion s

Dispe r sed sys t em s con s is t o f :a) particulate matter (dispersed phase).

b) dispersion medium (continuous medium).

Clas s i fica t ion o f d i spe r sed sys t em s ( a cco r d i n g t o

pa r t ic le s i ze ) :

MOLECULAR

DISPERSION

COLLOIDAL

DISPERSION

COARSE

DISPERSION

- Less than 1 um

- Particles undergorapid diffusion e.g. O2

& glucose

- 1 um to 500 um

- Very slow diffusione.g. colloidal silver sol.

- Greater than 500 um

- Dont diffuse

e.g. suspension &emulsion


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Col lo id a l D isper s ions

MOLECULAR

DISPERSION

COLLOIDAL

DISPERSION

COARSE

DISPERSION

-Particles invisiblein electron

microscope.

-Pass throughsemipermeablemembranes and

filter paper.

-Particles resolvedby electron

microscope.

- Pass throughfilter paper but not

pass throughsemipermeable

membrane.

-Particles arevisible under

ordinarymicroscope.

- Do not passthrough filter

paper or

semipermeablemembrane.


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Typ es o f co llo id a l sys te m s:

o According to the i n t e r ac t i on between particles ofdispersed phase & those of dispersion medium:

1) L y o p h ilic ( so lv en t lo v in g ) .

2 ) L y o p h o b ic ( s o lv en t h a t in g ) .

3 ) A s s o cia t io n (a m p h ip h ilic) .


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N.B.

DISPERSION MEDIUM = SOLVENT.

DISPERSED PHASE = MATERIAL = COLLOIDALPARTICLES.

SOL. = COLLOIDAL SOLUTION.


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1) Lyop h i lic col lo id s

Colloidal particles interact to an appreciable extent with the molecules of the

dispersion medium ( s o lv e n t lo v i n g ) .

Obtained simplyby dissolving the material in the solvent ( due to the highaffinity).

Typ es of lyop h i lic col loids ;

(Accord ing to type o f so lven t )

Hydr oph i li c co l lo ids ;

Solvent: w a t e r .

Example: acac i a ,i n s u l in . in wa t e r .

Lipo ph i li c co l lo ids ;

Solvent: n o n - a q u e o u s ,o r gan i c so lven t .

Example: r u b b e r

&polys tyrene .

S O; m a t e r i a l t h a t f o r m l y o p h il ic co l lo id i n a c e r t a in s o l v e n t m a y n o t d o s o

in a n o t h e r s o l v e n t , e.g.; acacia + water lyophilic colloid (hydrophilic type).

acacia + benzene NO lyophilic colloid formed.


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1 ) Ly o p h i l ic co l l o i d s

o the dispersed phase does not precipitate easily

o the sols are quite stable as the solute particlesurrounded by two stability factors:

a- negative or positive chargeb- layer of solvent

o If the dispersion medium is separated from thedispersed phase, the sol can be reconstituted by

simply remixing with the dispersion medium.Hence, these sols are called reversible sols


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2) Lyoph ob ic col lo ids

o Colloidal particles have very little or no attraction for the dispersion

medium ( s o lv e n t h a t i n g ) .

o Colloidal particles: in o r gan ic pa r t ic le s (e.g. gold, silver, sulfur.)Dispersion medium: w a t e r .

- These colloids are easily precipitated on the addition of smallamounts of electrolytes, by heating or by shaking

- Less stable as the particles surrounded only with a layer ofpositive or negative charge

- Once precipitated, it is not easy to reconstitute the sol bysimple mixing with the dispersion medium. Hence, these sols

are called irreversible sols.

o Not obtained simplyi.e need special method for preparation


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2) Lyop h ob ic co l lo id s

o M e th o d s t o p r e p a r e lyo p h o b iccol loids :

A) Dispersion methods:o coarse particles are reduced in sizeby;

1) Ultrasonic generator

2) Electric arc.

3) Colloid mill.


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1) U lt r a s o n i c ge n e r a t o r :

Dispersion achieved by high intensity UG at frequencym ore than

20,00 0 cycles/ second

2 ) Ele ct r ic a r c :

Involves production of an electric arc within the liquid anddispersion achieved byintense heat generated by the arc so somemetal of the electrodes dispersed as vapor then condense to colloidalparticles.

3) Col lo id a l m i ll:

Material shearedbetween 2 rapidly rotating close plates.

Low efficiency & reduce the size of small proportion of particlesonly.


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2 ) Elect r ic ar c:

ice

Dispersion medium(Water + kOH)


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B ) Co n d e n s a t io n m e t h o d s :

materials ofs ub co ll o ida l dimensions are caused to aggrega t e intoparticles with colloidal size range by;

1) Change in solvent.

2) Chemical reaction.

1) Ch a n ge in s o l ve n t :

Change in solvent Super saturation Formation &growth of nuclei.

( colloidal system formation)e.g. sulfur and alcohol inexcess of water

2) Ch em ica l r eac t ion :

Hydrogen sulfide

Br2 + H2S S + 2 HBr

HNO3 + H2S H2O + NO2 + S

Oxidatn. Sulfur atoms Sulfur sol.

Hydrolysis Ferric oxide sol. (red color).

Hydrogen sulfide + arsenous acid Double decomp. Arsenous sulfide sol.

Ferric chloride + water


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3. Association colloids:

o Certain molecules or ions termed amphiphile

(surface active agent SAA) are characterized by two

distinct regions of opposing solution affinities within

the same molecules or ions.


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- At low concentration: amphiphiles existseparately (subcolloidal size)

- At high concentration: form aggregates ormicelles (50 or more monomers) (colloidal

size)


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As with lyophilic sols, formation of association colloids is

spontaneous, provided that the concentration of the

amphiphile in solution exceeds the cmc.

Amphiphiles may be

1. Anionic (e.g., Na. lauryl sulfate)

2. Cationic (e.g., cetyl triethylammonium bromide)

3. Nonionic (e.g., polyoxyethylene lauryl ether)

4. Ampholytic (zwitterionic) e.g., dimethyl dodecyl

ammonio propane sulfonate.


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Comparison of properties of colloidal sol

Lyoph i l i c

( s o l v e n t - l o v i n g ) .

L yo p h o b i c

( s o l v e n t - h a t i n g ) .

A sso c ia t i o n (a m p h o p h i l i c ) .

Dispersed

phase

L arg e o rg a n i c

m o l e cu l e s l y i n g w i t h i n

co l lo ida l s i ze

I n o rg a n i c p a r t i c l e s

such as go ld o r

s i l ve r

Aggrega tes (m icel les) o f sma l l

o rgan ic mo lecu les o r ions

w hose s ize i s be low the

co l lo ida l s ize

So lv at io n So lv a t ed l i t t l e Hydroph i l i c o r l i poph i l i c po r t ion

o f th e mo lecu les i s so lva ted

d e p en d in g o n t h e m e d iu m

Pr e pa ra t io n Sp on t an eo us by

d isso lv ing in so lven t

Needs specia l

p ro ce d u re

Spon t aneous w hen conc. Of

a mp h i p h i l e s e xce e d s cm c

Viscosi t y Visco si t y i n cr eased as

the conc. i ncrease . A t

cer t a in conc. Gel so l

g e l f o rm a t i o n .

No t g re a t l y

increased due to

u n so l va t i o n

I ncreased as conc. Of

am ph iph i le i ncrease as

m ice l les no . i ncrease &

b e co me a symme t r i c .

Ef fect o fe l e c t ro l y t e s

Stab le in p resence o f

e lec t r o l y tes

D eso l v a t i on and s a l t i ng ou t

i n h igh c onc .

U nstab le due t o

neu t r a l i z at i on o f

c ha r ges on pa r t i c l es

Cm c i s reduced and sa l t i ng

o u t o ccu r a t h i g h sa l t co n c .


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Sha pe o f co llo ida l par t i cles :

o The more extended theparticle, the greater itsspecific surface & the greaterthe opportunity for attraction.

o Properties of colloids as Flow,sedimentation rate & O.P. areall affected by the shape ofthe particles.


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Pu r i fi ca t ion o f co llo ids

o 1) W h y ?

M a n y lyo p h o b ic s o ls c o n t a i n m o r e o r le s s m a t e r ia l in t r u e

s o lu t io n . wh i ch m a y b e u n d e s ir a b le fo r a n y n u m b e r o f

r easo n s ; e .g .,

n e le c t r o l yt e i m pu r i ti e s : ca u se t h e f loc cu la t i on o f t h e

sol .

2 ) H o w ?

a) Dialysis.

b) Electro dialysis.

c) Ultra filtration.


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a) - D ia l y si s:o Depend ondifference in size between colloidal

particles & molecular particles (impurities).

o Technique;1) usesemi permeable membrane (e.g. collodion

(nitrocellulose), cellophane).

2) pore size of used semi permeable membrane preventpassage of colloidal particles & permit passage ofsmall molecules & ions (impurities) such as urea,

glucose, and sodium chloride, to pass through.o A type of dialysis equipment; Neidle dialyzer

o At equilibrium, the colloidal material is retained in

compartment A, while the subcolloidal material is

distributed equally on both sides of the membrane.

By continually removing the liquid in compartmentB, it is possible to obtain colloidal material in A

that is free from subcolloidal contaminants


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b ) - El ect r o d i al y si s:o Technique;

o An electric potential may be used to

increase the rate of movement of ionic

impurities through a dialyzing

membrane and so provide rapid

purification.

o Electrodialysis is carried out in a three-

compartment vessel with electrodes inthe outer compartments containing

water and the sol in the center

compartment.

o A typical apparatus is shown in the figure. Application of electrical potential

causes cations to migrate to the negative electrode compartment and anions to

move to the positive electrode compartment, in both of which running water

ultimately removes the electrolyte.


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Ar t i fic ia l k idn ey m ach in e :

pa t i en t s b lood ( a r t e r i a l) pass through Cellopha n e co i ls ( i dea l s em i

p e r m e a b le m e m b r a n e fo rhaem odia lys i s ) .

ce lloph an e pa s s u r ea , glu cos e , e l ect r o lyt e s bu t do n t pa s sp l a s m a p r o t e ins & b lood ce l ls

p u r e d ia l yze d b l o o d e n t e r t h e b o d y a g a in t h r o u g h a v e in .

N .B .

success of the artificial kidney m achinedepends on its ability to reduce blood urea.

Cellophane coils are supported on a drumrotat ing in electrolyte solution (rinsing

fluid).


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Im p o r t a n ce o f t h e r in s in g s o lu t io n :

S u b s t a n c e s p r e s e n t i n exces s i n b lood (e .g. u r ea ) d i f fuse fr o m b lo o d to

t h e r i n s in g so lu t i o n .

S u b s t a n c e s w h i ch a r e de f ic ien t i n b lood (e .g. b i ca r bon a t e ) d i f fuse f rom

t h e r i n s in g s o lu t i o n t o b l o o d .

S u b s t a n c e s w h i ch a r e p r e s e n t in n o r m a l a m o u n t s in b lo o d a r e k e p t

u n a l t e r e d h a v e t h e s a m e co n c . I n b o t h b lo o d a n d r i n s in g s o lu t i o n .

Sui t a r t ificia l k idn ey m a ch in e ;


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P h ar m aceu t ica l ap p l ica t ion s o f co llo i ds ;

1) Col lo ida l s ilver iodide , s ilver ch lor ide & s i lver p r o te in ar e

effect ive g e r m i cid e s & n o t cau s e ir r it a t i on as i on i c s ilve r s a l t s .

2 ) Co l lo ida l copp er u s ed i n cancer .

3) Co l lo ida l go ld u s ed as d i a g n o s t i c a g e n t .

4 ) Co l lo ida l m er cur y u s ed i n s y p h i l i s .

5) Asso cia t ion col lo ids (SAA) ar e u sed to i nc rease so lu b i li t y &s tab i l i t y o f c e r t a in c o m p o u n d s i n a q u e o u s & o ily

p h a r m a c eu t ic a l p r e p a r a t io n s .


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7) B lo o d p la sm a s u b s t it u t es as de x t r a n , PVP & ge la t i n a r e

h y d r o p h ilic c o llo id s u s e d t o r e s t o r e o r m a i n t a i n b lo o d v o lu m e .

8 ) I r o n - d e x tr a n c o m p le x fo r m n o n -io n ic h y d r o p h i lic s o lsu s e d fo r t r e a t m e n t o f a n e m i a .

Su it P h a r m a c e u t ica l a p p lica t io n s o f

col lo ids ;

6 ) Ef f icien cy o f c e r t a i n s u b s t a n c e s is in c r e a s e d w h e n u s e d i n

c o llo id a l fo r m d u e t o la r g e su r fa c e a r e a .e.g. efficiency of kaolin in adsorbing toxins from GIT.e.g. efficiency of aluminum hydroxide as antacid.


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Pr op e r t ie s o f co llo ids

A) K in e t ic p r o p e r t ie s .

B) O p t ica l p r o p e r t ie s .

C) E le c t r i ca l p r op e r t ie s .


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A) Kin e t ic p r o p e r t ie s :

W h i ch r e la t e t o t h e m o t io n o f t h e p a r t ic le s w it h i n t h ed i sp e r s io n m e d iu m a s fo llo w in g:

Br o w n ia n m o t io n .

Diffus ion .

S e d i m e n t a t i o n .

Os m o t ic p r e s su r e .

Th e D o n n a n m e m b r a n e e ffe ct .

Viscosity.


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1) Br o w n ia n m o t io n :

o Def in i t ion: colloidal particles are subjected torandom collision with molecules of the dispersionmedium (solvent) so each particle move in irregularand complicated zigzag pathway.

o

First observed by Robert Brown (1827) with pollengrains suspended in water.

o The ve loc i ty of pa r t i c les i n c r e a s e s wi thd e c r e a s i n g pa r t i c le s ize an d v i scos i ty.

o In c rea s in g t he v i scos it y o f d i spe r s ionm e d i u m (by g lycer in) d e c r e a s e t h e n s t o p

Br o w n i a n m o t io n .


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2) Di ffu s ion :

o Defini t ion :o As a result of Brownian motion

particles pass (diffuse) from a region ofh i g h e r concentration to one with lo w e r

conc.

o Rate of diffusion is expressed by;

Fick s f i r s t law :dm/dt = -DA dc/dx

W h e r e d m is t h e m a s s o f s u b s t a n c ed i ffu s ing in t im e d t a cr o s s a n a r e aA u n d e r t h e in flu e n c e o f ac o n c en t r a t io n gr a d ie n t d C / d x.

Th e m in u s s ign d e n o t e s t h a t

d i ffu s ion t ak es p l ace in t h ed i r e c t io n o f d e c r e a s in gc o n c e n t r a t i o n .

D is the d i ffu s ion coef fi cien t .


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3 ) Se d i m e n t a t i on :

o Stok es law ;

V = 2 r 2 ( p -po ) g / 9

v: ve loc i ty o f sed imen ta t ion o f sphe r ica l pa r t i c le s .

p : den s i ty o f the sph e r ica l pa r t i c le s .

p o : d e n s i t y o f t h e m e d iu m .

: v iscos i ty o f th e m ed ium .

g : accele ra t ion d ue to g ra v ity .At sm al l p ar t i cle s ize ( le s s t h a n 0 .5 u m ) B r o w n i a n m o t io n i s

s ig n i fic a n t & t e n d t o p r e ve n t s e d i m e n t a t io n d u e t o g r a v it y &

p r o m o t e m ix in g in s t ea d .

s o , w e u s e a n u l t r a c e n t r i f u g e w h ic h p r o v id e s t r o n g er f o r c e s op r o m o t e s e d im e n t a t io n i n a m e a s u r a b le m a n n e r .


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4 ) Os m o t ic p r e s s u r e :

o Th e m e t h o d i s b a s e d o n Van ' s H of f' s law ;P = R TC / M

o F r o m t h e eq u a t io n ;

a ) Th e o s m o t ic p r e s s u r e (P ) d e p e n d s o n m o l a r c o n c . O f t h e

s o l u t e (C) & o n a b s o lu t e t em p . (T) .

b ) Th e o s m o t ic p r e s s u r e i s inver se ly p r o p o r t io n a l t om o le c u la r w e ig h t ( M) .

R= molar gas constant

o The equ a t i on is va lid fo r ve r y d il u t e s o lu t i on s in wh icht h e m o le c u le s d o n o t in t e r a c t m u t u a l ly.


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5 ) Th e D o n n a n m e m b r a n e e ffe ct .

o Def in i t ion:

Diffu s ion o f sm a l l i ons t h r ou gh am e m b r a n e w i ll b e a f fe ct e d b y t h ep r e s e n c e o f a c h a r ge d m a c r o m o l ec u let h a t ca n t p e n e t r a t e t h e m e m b r a n edu e t o i t s s i ze .

Appl ica t ion:1) Fac ili t a t in g t he abs o r p t i on o f

i on i zab l e d r ugs f rom GIT by co -a d m in i st r a t io n o f m a c r o m o le c u le s o f s a m e ch a r ge s o m u t u a l io n i cr e p u ls io n o c cu r s e .g

c o -a d m in i st r a t io n o f a n i o n icm a c r o m o l ec u le e .g . s o d i u m c a r b o x ym eth yl ce llu lose , wi th a d i ffu s ib le

an ion e .g . po t a s s iu m ben zyl pen i ci ll into e n h a n c e d i ffu s i o n of t he l a t e ra c r o s s b o d y m e m b r a n e s .


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6) v iscos i ty

o Def in i t ion :

o Th e r e s is t a n c e to flo w o f a s ys t e m u n d e r a na p p lie d p r e s su r e

o Viscosi ty of col loid a l low s 1- ca lcu l a t ion o f t h em o le cu la r w e igh t .

2 - P r o vid e u s e fu l in fo r m a t io n a b o u t th e sh a p e o f th e co llo ida l p a r t ic les .

o N .B .o S p h e r o c o l l o i d a l d i s pe r s ions a r e o f r e la t i ve ly lo w

viscosi ty.

o On t h e o t h e r h a n d Lin ea r co ll o ida l d i sp e r s io n s a r e o f

h igh viscos i ty .o I flin ea r co l lo ida l pa r t i c l e s coi l u p in t o sp h e r e s

Th e viscos i ty of t he s ys t em fa l ls d u e t o c h a n g in g t h e

s h a p e .


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B) O p t ica l p r op e r t ie s :

1) Ligh t sca t te r in g (Tyn d a ll e f fec t ) .

1) U lt r a m icr o s co p e .

2 ) E le ct r o n m icr o s co p e .


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1) Light scat ter ing (Tyn d al l effect )

o Tr u e s o lu t i ons d o n o t s c a tt e r l igh t a n da pp e a r c le a r bu t co llo ida l d i s pe r s ion sc on t a i n opa qu e pa r t i cle s t ha t do s c a tt e rligh t a n d t h u s a p p e a r t u r b id .

o Tyn d al l effect :

when a beam of light pass through a colloidal

sol, scattered light cause the sol to a p p e a r t u r b i d .

o I m por t a n c e o f ligh t s ca t t e r i ngm e a s u r e m e n t s :

1) Estimate particle size .

2) Estimate particle s h a p e .

3) Estimate particles i n t e r a c t i ons .


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2 ) U lt r a m ic r o s co p e :

o P a r t ic le s a p p e a r a s s p o t s

o f l igh t aga ins t t h e da r k

b a c k gr o u n d o f th e

m i c r o s c o p e .

o U s e d in t h e t e ch n iq u e o f

m ic r o e l ec t r o p h o r e s is fo r

m e a s u r in g p a r t ic le

c h a r g e .

o Give ac tua l p i c tu r e o f t hepa r t ic le s ( u p t o 5A) .

o U s e d t o o b s e r v e t h e s iz e ,s h a p e a n d s tr u ct u r e o f

so l s .o H ig h e n e r g y e le c tr o n

b e a m s a r e u s e d . (h a v eg r e a t e r r e s o lvin g p o w e r )

o O n e d is a d v a n t a g e is ;

o n ly d r ie d s a m p l es c a n b eexam in ed . Not givein fo r m a t io n o ns o lva t i on .

3 ) E le ct r o n

m i c r o s c o p e :


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C) E lec t r ica l p r op er t ie s :

a ) E le c tr ica l p r op e r t ie s o f in t e r fa c e s .

b ) The e le c t r i ca l d ou b l e la ye r .


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a ) E lect r i ca l p r op e r t i e s o f in te r faces :

M o st su r fa ces a cq uir e a su r fa ce e le ct r ic ch a r ge

w h en b r o u gh t in to con ta ct w it h a n a q u eo u s

m e d iu m , th e p r in cip a l ch a r gin g m e ch a n ism s

b e in g a s fo llo w s:

1) Ion d i s so lu t ion .

2 ) I o n iza t io n .

3 ) I o n a d s o r p t io n .


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1) Ion d isso lu t ion :

o Surface charge of colloidal particle is con t r o l led b y the charge of ionpresent in excess in the medium.

o E xa m p le s ; 1) AgN o 3 + N a I AgI + N a N o3

a) silver iodide in a solution with excess iodide Particles acquire - ve

b) Aluminum hydroxide in a solution with excess hydroxide

P o t e n t ia l d e t e r m in in g io n s : ions whose conc. determine theelectric potential at the particle surface (e.g. Ag+ , I -, H+, OH- )

charge & vice versa. if excess Ag the charge will be +ve since the conc.Of Ag and I determine the electric potential

particles acquire ve charge & vice versa.

2) Ion iza t ion


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2) Ion iza t ion

o Surface charge of colloidal particle is controlled bytheionization of surface groupings

o E x a m p l e s ;

a)polystyrene latex has carboxylic acid group at the surface, ionize to givenegatively charged particles.

b) acidic drugs as ibuprofen & na lidixic acidacquire surface negative

charged.

c)Am ino a cids & prot ein s have carboxyl & amino groups whose ionizationdepend on the pH as follow;

-NH3-R-COO

-NH3-R-COOH

+ +

At high PH

Alkaline medium

Negatively charged

COOH COO-

Zwitter ion

Iso electric point

Zero charge

At low PH

Acidic medium

Positively charged

NH2 NH3+

NH2-R-COO


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Su i t ion iza t ion ;

o I so e le c t r i c po i n t :

o p H at wh ich + ve c h a r g e s = -ve c h a r g e s ,

o i .e. n e t ch a r ge o f t h e a m in o a c id = z er o .

o I t is a de fin i t e pH specif ic fo r e a c h p r o t e in .

o At t h i s p H p r o t e i n is leas t so lub le & pr ec ip i t a t ed .

o Q ; H o w c a n yo u p r e cip i ta t e in s u l in ? ??

o BY ADJUSTING THEpHOF the SOLUTIONTO THE ISO ELECTRIC POINT OF INSULIN

(PH 5.2) .


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3 ) I o n a d s o r p t io n :

o Sur face cha r ge o f co l lo ida l p a r t ic le is con t r o l led b y th e

u n e q u a l a d s o r p t i o n o f o p p o s it e ly c h a r g ed i o n s

o E x a m p l e s ;

o S u r fa c e s o f s o l in w a t e r a r e m o r e o ft e n ve c h a r g e d

tha n + ve cha r ged ? !!!

B e c a u s e ca t io n s a r e m o r e h y d r a t e d t h a n a n i o n s s o

c a t io n s r e s i d e in t h e b u lk w h ile le s s h yd r a t e d a n io n s

a d s o r b e d o n t h e s u r f a ce .

b) T he e lec t r i ca l d ou b l e laye r :


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b) T he e lec t r i ca l d ou b l e laye r :

AgNO3 + Na I AgI +Na NO3

D e ve lo p m e n t o f a n e t c h a r ge a t t h e p a r t ic le s u r f a c e a ffe c ts t h ed i s tr ib u t io n o f io n s in t h e s u r r o u n d i n g in t e r f a cia l r e g io n ,

As a r e s u lt : c o n c e n t r a t io n o f c o u n t e r i o n s in c r e a s e a t t h es u r f a c e ,

Th u s , a n e le c tr i c a l d o u b l e la y e r e x is t s a r o u n d e a c h p a r t ic le .

E x a m p l e ;

Def in i t ion:

I-

Na+At xs NaI :

AgI

AgIAgIAgI

AgIAgI

AgI

( N.B. Vice versa if xs AgNO3 )

o S ilve r io d i d e s o l s ca n b e p r e p a r e d b y t h e r e a c t io n ,


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n AgN0 3 + Na l ---- Agl + Na N0 3

o I n t h e bu lk of AgI pa r t i cles 1 : 1 r a t io of Ag+ an d I -

o I f t h e r e a c t io n is c a r r ie d o u t w it h a n exces s s i lve r n it r a t e ,

t h e r e w ill b e m o r e Ag+ t h a n l- io n s in t h e s u r fa c e o f t h e

pa r t ic le s The pa r t ic le s wi ll t hu s be p os i t ive ly cha r ged

a n d t h e c o u n t e r i o n s s u r r o u n d in g t h e m w ill b e N 0 3 -.

o Th e c o m b i n a t i o n o f t h e p os i t ive ly cha r ged s u r fa c e a n d t h ea t m o s p h e r e o f co u n t e r io n s s u r r o u n d i n g i t is c a lle d th e

e l ect r i c do u b le laye r .

o I f t h e r e a c t io n is c a r r ie d o u t w it h a n exces s Na I , t he r e wi ll

b e m o r e l- t h a n Ag + io n s in t h e s u r fa c e o f t h e p a r t ic le s

The pa r t ic le s wi ll t hu s be n ega t ive ly ch a r ged a n d t h e

co u n t e r io n s s u r r o u n d i n g th e m w ill b e N a + .

Colloidal Disp[1]_ppt [Compatibility Mode]

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