colloidally

Colloidally is an adverb used to describe actions, properties, or processes that occur in or pertain to colloids. In colloid science, something described colloidally has been produced, stabilized, or dispersed as a colloid—a system in which finely divided particles or droplets are dispersed in a continuous medium and do not immediately separate.

A colloid consists of a dispersed phase and a continuous phase. The dispersed phase particles are typically 1 nanometer to 1 micrometer in size and may be solid, liquid, or gaseous, depending on the system. Common natural and engineered examples include milk fat droplets in water, fog droplets in air, and colloidal gold. The small size and Brownian motion of the particles help keep the dispersion from readily settling or coalescing.

Stability of colloidal suspensions arises from electrostatic or steric stabilization. Electrostatic stabilization relies on surface charges and the resulting repulsion between particles, while steric stabilization uses adsorbed polymers or stabilizers to create a physical barrier. The DLVO theory describes the balance between attractive van der Waals forces and repulsive electrostatic forces. The zeta potential is a common measure of stability, and the Tyndall effect is a diagnostic optical property of many colloids.

Applications of colloidally dispersed systems span food science, cosmetics, pharmaceuticals, paints and coatings, and environmental engineering. Characterization methods include dynamic light scattering for size distribution, zeta potential measurements, and electron or atomic force microscopy for morphology.