Colloid Chemistry

colloid chemistry [¦käl‚ȯid ′kem·ə·strē]

(physical chemistry)

The scientific study of matter whose size is approximately 10 to 10,000 angstroms (1 to 1000 nanometers), and which exists as a suspension in a continuous medium, especially a liquid, solid, or gaseous substance.

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Colloid Chemistry 

the traditional term for the physical chemistry of disperse systems and surface phenomena. It took shape as an independent science in the 1860’s. Since that time its subject matter and methods have changed markedly. In the period of the establishment of colloid chemistry, the term “colloids” was applied to gluelike amorphous bodies (as opposed to crystalline bodies, or “crystalloids”). At present the term “colloids” is a synonym for maximally disperse (microheterogeneous) systems with very highly developed phase interface surfaces.

Colloid chemistry deals with the unique processes and phenomena resulting from the special features of the highly disperse state, such as spontaneous enlargement of particles in the solid dispersed phase or drops of liquid (coagulation and coalescence), a manifestation of the thermodynamic (aggregate) instability of disperse systems; the gelation of liquid disperse systems, with the formation of gels and the appearance of three-dimensional disperse structures; the interaction of contiguous bodies, including friction and adhesion, and the change in the interaction under the influence of substances adsorbed on contact surfaces; phenomena in thin liquid and solid films; and the spontaneous dispersion of liquids and solids. The characteristic features of the major objects of study in colloid chemistry have brought about the development of specific research methods, such as ultracentrifuging, ultrafiltration, dialysis and electrodialysis, electroosmosis and electrophoresis, various methods of fractionation and dispersion analysis, ultramicroscopy, electron microscopy, and nephelometry.

Modern colloid chemistry includes the following major areas:

(1) Kinetic molecular phenomena (Brownian movement and diffusion) in disperse systems; hydrodynamic characteristics of disperse systems; and dispersion analysis.

(2) Surface phenomena: adsorption (thermodynamics and kinetics); wetting, adhesion, and surface chemistry processes in disperse systems; and the structure and properties of surface or adsorption layers.

(3) The theory of the appearance of a new, dispersed phase in a metastable (supersaturated) medium; condensation methods of formation of disperse systems.

(4) The theory of the stability, coagulation, and stabilization of colloid-disperse systems and the structure of particles of the dispersed phase, or micelles.

(5) The physicochemical mechanics of disperse systems, including the theory of mechanical dispersion, phenomena of adsorption reduction of the strength of solids, and the rheology of disperse systems; and the formation and mechanical properties of the three-dimensional structures in disperse systems.

(6) Electric and electrokinetic effects in disperse systems.

(7) Optical effects in disperse systems (colloid optics): dispersion and absorption of light; the colloid chemistry of photographic processes.

All of nature—animals and plants, and hydrosphere and atmosphere, and the earth’s crust and core—is a complex set of the most varied coarse-disperse and colloid-disperse systems. The disperse state is universal, and any object may enter it under suitable conditions. This is the reason for the special position occupied by colloid chemistry, whose development is proceeding in direct contact and constant interaction with many often unrelated scientific fields, as well as industrial and agricultural research and practice. The development of colloid chemistry is related to current problems in various fields of the natural sciences and technology.

The scientific basis for industrial processes that involve disperse systems is being developed in colloid chemistry. Such areas include the technology of building materials and silicates (particularly ceramics); the technology of plastics, cured rubber, and paints and lacquers using highly disperse pigments and fillers; the technology of drilling in rock and the mechanical processing of solids, including metals; processes of heterogeneous catalysis; and adsorption processes. The study of disperse structures is the basis for the study of materials of the future, without which technological progress is impossible. Colloid chemistry indicates rational approaches to the breakup of oil emulsions (the demulsification of crude oil is one of the most important methods of removing water and salts); the preparation of disperse forms (the most efficient forms) of pesticides that are widely used in agriculture; and the use of surface-active substances in washing and cleaning materials, emulsifiers, flotation agents, and lubricatingoil additives. The most important problems in geology and geochemistry (the origin and transformation of minerals and rocks; weathering) and of soil science and soil mechanics are closely related to the laws governing the behavior of multicomponent microheterogeneous systems. The study of aerodisperse systems (aerosols) is important in meteorology in the study of atmospheric precipitation. Along with biochemistry and the physical chemistry of polymers, colloid chemistry is the basis for the study of biological structures and the origin and development of life.

REFERENCES

Rebinder, P. A., and N. A. Figurovskii. “Kolloidnaia khimiia. In Razvitie fizicheskoi khimii v SSSR. Edited by la. I. Gerasimov. Moscow, 1967. Page 239.
Peskov, N. P. Fiziko-khimicheskie osnovy kolloidnoi nauki, 2nd ed. Moscow-Leningrad, 1934.
Dumanskii, A. V. Uchenie o kolloidakh, 3rd ed. Moscow-Leningrad, 1948.
Zhukov, I. I. Kolloidnaia khimiia, part 1. Leningrad, 1949.
Sheludko, A. Kolloidnaia khimiia. Moscow, 1960. (Translated from Bulgarian.)
Voiutskii, S. S. Kurs kolloidnoi khimii. Moscow, 1964.
Pasynskii, A. G. Kolloidnaia khimiia, 3rd ed. Moscow, 1968.
Pisarenko, A. G., K. A. Pospelova, and A. G. Iakovlev. Kurs kolloidnoi khimii, 3rd ed. Moscow, 1969.
Svedberg, T. Kolloidnaia khimiia, 2nd ed. Moscow [1930]. (Translated from English.)
Freundlich, H. Kapillarchemie, vols. 1–2. Leipzig, 1930–32.
Colloid Science, vols. 1–2. Edited by H. R. Kruyt. New York, 1949–52.
Nauka o kolloidakh, vol. 1. Edited by H. R. Kruyt. Moscow, 1955. (Translated from English.)
Surface and Colloid Science, vols. 1–4. Edited by E. Matijevic. New York, 1969–71.

P. A. REBINDER and L. A. SHITS