Suspenzije

Suspenzije, or suspensions, are heterogenous mixtures in which solid particles are dispersed in a liquid medium. The solid phase is not dissolved but remains suspended, and the mixture often appears cloudy or opaque. Particle sizes typically range from about 1 micrometer up to several hundred micrometers. Because the dispersed particles are heavier than the liquid, they tend to settle under gravity over time, although agitation can keep them dispersed temporarily.

Suspenzije are distinguished from solutions, where the solute is dissolved at the molecular or ionic level, and from colloids, where particle sizes range roughly from 1 nanometer to 1 micrometer and Brownian motion or stabilizers help prevent rapid sedimentation.

Stability of suspensions is a balance between gravitational settling and forces that hinder aggregation, such as electrostatic repulsion or steric stabilization. Stabilizers like polymers, surfactants, or electrolytes, increased viscosity, and proper pH can extend shelf life.

Preparation and processing include vigorous stirring or shaking to form a dispersion, milling or grinding to reduce particle size, and ultrasonication. Storage typically requires occasional shaking to resuspend settled solids.

Separation and removal of the solid phase can be achieved by decantation, filtration, sedimentation, or centrifugation.

Common examples include muddy water, chalk or clay in water, flour in water, and pharmaceutical suspensions where insoluble drugs are dispersed in a liquid vehicle. Silicates in paints and suspensions in food products are other examples.

Note: In some contexts, the term suspenzije may also refer to suspension systems in vehicles; see suspension (mechanics) for details.