Kolloidi

Kolloidi are substances in which microscopic particles are dispersed in another phase to form a colloidal system. The dispersed phase consists of particles typically between about 1 nanometer and 1000 nanometers in size, meaning they are larger than ordinary molecules but too small to be seen with the naked eye. The continuous medium can be a liquid, a gas, or a solid. The term kolloid (colloid) derives from Greek and was coined to describe a glue-like distribution of particles.

There are several classes of kolloidi. Lyophilic colloids (solvent-attracting) tend to be more stable in their medium and can form gels or sols that are relatively easy to redisperse. Lyophobic colloids (solvent-repelling) are often less stable and require stabilizers such as charges or polymers to prevent aggregation. Stability is influenced by factors such as charge, ionic strength, pH, and the presence of stabilizing agents. Mechanisms include electrostatic repulsion, steric hindrance by adsorbed molecules, and polymeric stabilization.

Key properties of kolloidi include the Tyndall effect (scattering of light by particles in the colloid) and Brownian motion, which helps prevent sedimentation of small particles. Kolloidi can be prepared by breaking down larger particles (dispersion) or by condensation from smaller units (precipitation), and they can be characterized by techniques that assess size distribution and stability.

Common examples range from milk and fog to paint, ink, and many cosmetic or pharmaceutical formulations. Kolloidi have wide applications in food science, medicine, materials science, and environmental technology, where controlled particle size and stability determine performance and safety.