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General characteristic of the dispersed systems. Plan 1. The main concepts and determination 2. Classification of the disperse d systems 3. Preparation methods of the disperse d systems 4. purification methods of the disperse d systems. Assistant Kozachok S.S. prepared. - PowerPoint PPT Presentation
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General characteristic of the dispersed systems
Plan1. The main concepts and
determination2. Classification of the dispersed
systems 3. Preparation methods of the
dispersed systems 4. purification methods of the
dispersed systems Assistant Kozachok S.S. prepared
PHASES OF COLLOIDS THEIR CLASSIFICATIONA colloidal solution is of heterogeneous nature. It consists of two phases i.e. a dispersed phase and a dispersion medium.
Dispersed phase. It is the component present in small proportion and is just like a solute in a solution.
Classification of the dispersed systems according to the
particle sizeUltramicroheterogeneous
10-7 ÷ 10-9 м
Microheterogeneous10-4 ÷ 10-7 м
Coarse-dispersion>10-4 м
Colloidal particles can be classified according to shape as
corpuscular, laminar or linearMany colloidal systems do, in fact, contain spherical or nearly spherical particles. Emulsions, latexes, liquid aerosols, etc., contain spherical particles. Certain protein molecules are approximately spherical. The crystallite particles in dispersions such as gold and silver iodide sols are sufficiently symmetrical to behave like spheres.
Some model representations for non-spherical particles
Classification of dispersed systems according to the particle-particle interaction
Free dispersion or Free dispersion or no no sharp line of sharp line of demarcation demarcation (particles moving free)
sols
Not free dispersion or Not free dispersion or sharp line of sharp line of demarcationdemarcation
(particle-particle interaction between
themself)gels, foams
Classification of dispersed systems according to the particle-dispersion medium
interaction
Lyophilic (liquid-loving)
good interaction of dispersed particle with dispersed medium
emulsion and a water-in-oil
Lyophobic (liquid-hating)
(no any interaction of dispersed particle with dispersed medium)emulsion an oil-in water
Condensation methods of the preparation of the colloidal solutions. It bases on the appearing of a new phase in the homogenius phase according to the joining of molecules, atoms,ions.
Physical Condensation from a pair, the substitution of a poor solvent
ChemicalFeCI3+3H2O → Fe(OH)3 +3HCl
AgNO3 + KCl → AgCl + KNO3
2H2S + SO2 → 3S + 2H2O
Ag2O + H2 → 2Ag + H 2O
Dispersion method of the preparation of colloid solution
MechanicalUsing crusher, mill, mixer
Electricalusing the instruments for electrolytic
sprayingAcoustic
using ultrasound
PeptisationPeptisation – chemical dispergation is transfering the
sediment in the state of sol
BallBall (а) (а) andand colloidcolloid ( (bb) ) mill
а)а) bb))
A further modification of dialysis is the technique of electrodialysis
Ultrafiltration:а) vacuum; b) preassure c) gel permeation chromatography
а) b)
c) Another most valuable development of the ultrafiltration principle is the technique of gel permeation chromatography for the separation of the components of a polymeric sample and determination of the relative molecular mass distribution. The usual experimental arrangement involves the application of a pressure to force polymer solution through a chromatographic column filled with porous beads. The larger polymer molecules tend not to enter the pores of the beads and so pass through the column relatively quickly, whereas the smaller polymer molecules tend to diffuse through the pore structure of the beads and so take longer to pass through the column. The eluted polymer can be detected and estimated by measuring the refractive index of the emerging solution, and the relationship between retention time and relative molecular mass is determined by calibrating the apparatus with polymer fractions which have been characterised by other methods, such as osmotic pressure