A colloid or colloidal dispersion, is a form of matter intermediate between a true solution and a mixture (suspension). Microscopic particles of one substance, said to be in the dispersed or solute phase, are distributed throughout another, said to be in the dispersing, continuous, or solvent phase.
The field was introduced in 1861 by Scottish scientist Thomas Graham.
Colloidal sizes range from 0.001 to 1 micrometers in any dimension. Dispersions where the particle size is in this range are referred to as colloidal aerosols, colloidal emulsions, colloidal foams, or colloidal suspensions or dispersions. Colloids may be colored or translucent because of the Tyndall effect. The Tyndall effect is the scattering of light by particles in the colloid.
A colloid is a state of matter characterized by a large surface area per unit volume or unit mass.
Colloidal systems include solid-solid (metal alloys); solid-liquid (a suspension such as muddy water); solid-gas (smoke, airborne dust, aerosol inhalers); liquid-solid (butter, creams, ointments, lotions, photographic emulsions, paints); liquid-liquid (an emulsion such as milk); liquid-gas (fog, mist, aerosol sprays); gas-solid (marshmallows); and gas-liquid (foams).
Colloid and surface chemistry is involved in every segment and niche of clinical diagnostics and the specialty chemical, petrochemical, pharmaceutical, biopharmaceutical, and cosmetic industries.
Colloid and Interface Science is an important area of knowledge which underpins a very wide variety of both fundamental and applied science.
Colloids include a variety of complex materials, eg liquids in liquids (emulsions), solids in liquids (dispersions), liquids in gases (aerosols or foams), solid dispersions and biosystems, where the interactions between phases and at interfaces are dominant aspects of the system’s behaviour.
Colloid and formulation science is a critical capability in industrial design and manufacture of just about any chemical and many bio-industry “finished” products, eg: medicines and biocides; foods; personal care and household care products; ceramics and composites; paints and coatings to name just a few.
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