kolloidaler

Kolloidal systems, or colloidaler Stoffe in German, refer to mixtures in which particles of a dispersed phase are distributed in a continuous phase at microscopic scales. The dispersed particles typically range from about 1 nanometer to 1000 nanometers and do not settle rapidly because of Brownian motion and kinetic stabilization. Colloids often exhibit the Tyndall effect, meaning a beam of light becomes visible when passing through the mixture due to scattering by the particles.

Stability in colloids arises from electrostatic repulsion, steric hindrance by adsorbed molecules, or a combination of both. The magnitude of surface charge, measured as zeta potential, is commonly used as an indicator of stability; values with large absolute magnitude—often above ±25 to ±30 millivolts—suggest greater resistance to aggregation. The DLVO theory describes the balance between attractive van der Waals forces and repulsive electrostatic forces that governs colloidal stability.

Common types include sols (solid particles in liquids), gels (three‑dimensional networks in a liquid), emulsions (droplets of one liquid dispersed in another immiscible liquid), suspensions (undissolved solids in a liquid), foams (gas in liquids or solids), and aerosols (liquid or solid particles dispersed in a gas). Examples widely encountered are ink, paint, milk, mayonnaise, fog, and many cosmetic or pharmaceutical formulations.

Applications span food, medicine, cosmetics, materials science, and environmental technology. Preparation and stabilization rely on surfactants, polymers, pH control, and ionic strength adjustment. Colloids are studied using techniques such as dynamic light scattering, electron microscopy, and measurements of zeta potential to determine particle size distributions and stability.