kolloide

Kolloide, or colloids in English, are heterogeneous systems in which a dispersed phase of ultrafine particles or macromolecules is distributed in a continuous medium. The particle size typically lies between about 1 nanometer and 1 micrometer. Colloidal particles are larger than those in true solutions but too small to be seen with the naked eye and they generally do not sediment rapidly under gravity.

Colloids are classified by the state of the dispersed phase and the medium. Common forms include sols (solid in liquid), gels (a network in a liquid), emulsions (liquid in liquid), aerosols (solid or liquid in gas), and foams. Examples range from milk (fat droplets in water) and fog (water droplets in air) to ink (pigment particles in liquid). Some colloids are lyophilic, others lyophobic, and stabilization often requires charges, polymers, or surfactants.

Stability in colloids results from forces that prevent aggregation, such as electrostatic repulsion, steric hindrance, or network formation. Brownian motion opposes sedimentation, and the Tyndall effect can distinguish colloids by light scattering. Changes in pH, ionic strength, or temperature can induce coagulation or flocculation, removing the colloidal stabilizers.

Applications span food, medicine, cosmetics, and materials science. Colloidal systems are used in pharmaceutical suspensions, diagnostic imaging, nanoparticle syntheses, and coatings. Studying colloids also informs understanding of rain, aerosols, and biological fluids.

History and terminology: The term colloid was introduced in the 19th century by Thomas Graham to distinguish dispersed systems from true solutions. Since then, colloid science has become a foundational area in chemistry, physics, and materials science.