s edimentation t heory (a) gravitational sedimentation (b) centrifugal sedimentation
DESCRIPTION
2.2 K inetic p roperty. S edimentation. Motion of heavy particles settle down in response to an external force such as gravity , centrifugal force or electric force Rate of sedimentation depends on the strength of the field, masses and shapes of the particles. S edimentation T heory - PowerPoint PPT PresentationTRANSCRIPT
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Motion of heavy particles settle down in response to an exter nal force such as gravity , centrifugal force or electric force
Rate of sedimentation depends on the strength of the field, masses and shapes of the particles
Sedimentation Theory(a) Gravitational sedimentation(b) Centrifugal sedimentation
-Sedimentation velocity-Sedimentation Equilibrium
2.2 Kinetic property
Sedimentation
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(a) Gravitational Sedimentation
m
F1
F2Fb (buoyancy)
Fg (gravity)
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(a) Gravitational Sedimentation
m
F1 = fVg
F2 = mg(1 - 2/1)
At equilibrium :fVg = mg(1 - 2/1)
m = fVg
g(1 - 2/1)M = fNAVg
g(1 - 2/1)1 = density of particle2 = density of medium
F1
F2
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(b) Centrifugal Sedimentation
•sedimentation velocity•sedimentation equilibrium
= angular velocity (rpm)
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b.1 Sedimentation velocity
an analytical ultracentrifugation method that measures the rate at which molecules move in response to centrifugal force generated in a centrifuge .This sedimentation rate provides information about both the molecular mass and the shape of molecules .In some cases this technique can also measure diffusion coefficients (D).
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b.1 Sedimentation velocity
F1
F1 = fV = f(dr/dt) F2 = m2r (1 - 2/1)
At equilibrium :f(dr/dt) = m 2r (1 - 2/1)
M = sfNA = sRT
(1 - 2/1) D(1 - 2/1)
S = (dr/dt) = m(1 - 2/1) 2r f
r
F2
s = sedimentation coefficient ( Svedberg,1Sv=10-13 s)
~ 80,000 rpm
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b.2 Sedimentation equlibrium
M = 2RT ln (C2/C1) (1 - 2/1) 2 (r2
2-r12)
~ 10,000 rpm
=
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Assignment-3
GGrouproup P PresentationresentationCComparing to omparing to sedimentationsedimentation
G1 : G1 : precipitation,precipitation, aggregationaggregation G2 : G2 : coagulation,coagulation, flocculationflocculation
(10 students per group)
(5 min)
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3.3. O Opticalptical p property roperty
A colloidal system contains particles that affect a light beam by scattering and absorption .
If the particles are of a size comparable to the wavelength () of light or larger, they scatter or absorb light independently .
The same thing happens if they are separated by distances comparable to or greater than the wavelength () of light .
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3.3. C Commonommon O Opticalptical pphenomena henomena
the interaction of light from the sun or moon with the atmosphere, clouds, water, or dust and other particulates
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Assignment-4
GGroup roup PPresentationresentationG3 : Rayleigh Scattering G3 : Rayleigh Scattering G4 : RamanG4 : Raman ScatteringScatteringG5 : Mie ScatteringG5 : Mie ScatteringG6 : Bragg ScatteringG6 : Bragg Scattering
(10 students per group)
(5 min)