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General characteristics of colloids, differentiation based on particle size, medium or nature. Tyndall effect, Rayleigh scattering
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“kólla”-comes Greek word meaning ‘glue’.
“iod”-like First coined 1605 < chemist < chymist
< Latin alchimista < Arabic الكيمياء (al-kīmiya’) < article ال- (al-) + Ancient Greek χυμεία (khumeia, “art of alloying metals”) < χύμα (khuma, “fluid”)< χυμός (khumos, “juice”) < χέω (kheō, “I pour”).
Thomas Graham (1805-1869)
Glasgow, Scotland
Colloid solution Colloid system
Colloid Colloid chemistry Colloid science
1. Selmi2. Graham 3. Tyndall
Group Diameter a (m) Dispersion D=1/a (m-1)
1. Suspension >10-7 >107
2. Colloid =10-7-10-9 =107-109
3. Solution <10-9 <109
1
2,10 VS
S
S1,2-interface area between dispersed (1) and continuous (2) phase (m2)V1-volume of dispersed phase (m3)
1. By a diameter of particle (а) 2. By a reverse quantity of diameter of particle (1/а)3. By a specific surface area of dispersed phase (S0)
ColloidMicelle, microgel
Polymer
DNA
Protein
Molecule
Atom
Мixture
Molecular mass
Radius
Specific surface area
Colloids can be classified as follows: (by aggregate state)
Medium / Phases
Dispersed phase
Gas Liquid Solid
Continuous medium
Gas
NONE(All gases are
mutually miscible)
Liquid aerosolExamples: fog, mist,
hair sprays
Solid aerosolExamples: smoke,
cloud, air particulates
Liquid
FoamExample:
whipped cream, Shaving cream
EmulsionExamples: milk,
mayonnaise, hand cream
SolExamples:
pigmented ink, blood
Solid
Solid foamExamples: aerogel, styrofoam, pumice
GelExamples: agar,
gelatin, jelly, silicagel, opal
Solid solExample:
cranberry glass
F12=12S12
F12-all excess free energy on interface of phases12-free energy per unit areaS12-all interface area of (1) and (2) phases
m[Fe(OH)3]
Fe+3Fe+3
Fe+3
Fe+3
Fe+3
Fe+3
Fe+3
Fe+3
Fe+3
Cl-Cl- Cl-
Cl-
Cl-Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl- Cl-
Cl-
Cl-
Cl-
FeCl3+H2O
1. The solution of all ‘colloid substance’ has property scattering the light. 2. The diffusion of particle is slow effected in colloidal solution. 3. Osmosis pressure is very low and unstable4. Dialysis, The process of separating the particles of colloid from those of
crystalloid, by means of diffusion through a suitable membrane is called dialysis.
5. Coagulation, a process in which dispersed colloidal particles agglomerate.
6. Electrophoresis, it is the motion of dispersed particles relative to a fluid under the influence of a spatially uniform electric field
•Surface phenomenon•Physical and chemical characteristics of the dispersion system•Stabilization of a colloidal dispersion
AgNO3 + KI AgI + KNO3
Thank you for your attention!