Among them, the substance dispersed in the dispersion system is called dispersion phase (or dispersion); The substance that plays the role of containing dispersion is called dispersion medium (or dispersant). [1-2]
Classification according to the size of dispersion particles
Dispersion system | solution | colloid | Turbid liquid |
Particle composition | Single molecule or ion | An aggregate of several molecules or a single macromolecule | Small solid particles or droplets formed by the aggregation of a large number of molecules |
Particle size | ＜ 1nm | 1 nm~100 nm | ＞ 100 nm |
appearance | Uniformity Transparent stable | Uniformity Transparent Metastable | Uneven Turbidity Unstable, easy to precipitate or delaminate after standing |
nature | It can penetrate the semi permeable membrane It can pass through filter paper No Tindall effect | It cannot penetrate the semipermeable membrane It can pass through filter paper With Tindall effect | It cannot penetrate the semipermeable membrane It cannot pass through the filter paper The turbid liquid with particle diameter close to 100 nm has the Tyndall effect |
example | Salt water, iodine | Fe(OH) three colloid | Slurry water, oil-water, milk |
reference material | [1-3] |
Classification by dispersed phase and medium aggregation state
Formed by using liquid as dispersion medium Sol 。 When the dispersed phase is in different states, different liquid sols are formed: A- Solid sol ， 
Hydrosol 2. Solid sol
A sol formed by using a solid as a dispersion medium. When the dispersed phase is in different states, different solid sols are formed: A, solid solid sol,
For example: Tinted glass , incomplete mutually dissolvable Alloy; B、 Solid liquid sol, such as: Pearl , some gemstone ； C、 Solid aerosol, such as foam plastic 3. Aerosol
Sol formed by using gas as dispersion medium. When the dispersed phase is solid or liquid, gas-solid or gas-liquid sol is formed, but there is no gas-
Aerosol, because different gases are mixed into a single-phase homogeneous system, does not belong to the scope of colloid: A. Gas solid sol, such as smoke, dust laden air
aerosol Classification according to the stability of colloidal solution
Insoluble matter with radius between 1nm and 100nm Solid particle Dispersed in liquid medium Phase interface , easy to agglomerate, yes thermodynamics The unstable system on the. Once the medium is evaporated, the sol can not be formed when the medium is added again. It is an irreversible system, such as Ferric hydroxide Sol Silver iodide Sol, etc. This is colloid Dispersion system The main contents of the study. 2、 Hydrophile sol Radius falling within the range of colloidal particles macromolecule Dissolve in a suitable solvent. Once the solvent is evaporated, the macromolecular compound will coagulate Gather, then add solvent And can form sol. Hydrophilic sol is thermodynamically stable and reversible system. 3. Characteristics of Hydrophobic Sols
(1) Unique dispersion degree
The particle size is between, so it diffuses slowly and cannot penetrate Semipermeable membrane , low osmotic pressure but strong dynamic stability and (2) Polyphase inhomogeneity
Nanometer sized particles are agglomerated by many ions or molecules with complex structure, some of which maintain the Insoluble Original salt crystal structure ， and Particle size Different, there is an obvious phase interface with the medium, specific surface Very big. (3) Thermodynamic instability
Because the particles are small and larger than the surface, surface free energy High is a thermodynamic unstable system, with a tendency to spontaneously reduce the surface free energy, that is, low Particles will automatically coalesce Large particle 。 4. Hydrophobic sol forming necessary condition (1) Dispersed phase solubility Be small; (2) There must also be stabilizer Otherwise, the colloidal particles are easy to coalesce and settle. 
