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The term colloidal suspension refers unambiguously to the overall mixture (although a narrower sense of the word suspension is distinguished from colloids by larger particle size). A colloid has a dispersed phase (the suspended particles) and a continuous phase (the medium of suspension).
In materials science and colloidal chemistry, the term colloidal particle refers to a small amount of matter having a size typical for colloids and with a clear phase boundary. The dispersed-phase particles have a diameter between approximately 1 and 1000 nanometers .
A colloidal solution is a heterogeneous mixture in which the particle size of the substance is intermediate between a true solution and a suspension, i.e. between 1–1000 nm. Smoke from a fire is an example of a colloidal system in which tiny particles of solid float in air.
Due to the various reported definitions of solutions, colloids, and suspensions provided in the literature, it is difficult to label each classification with a specific particle size range. The International Union of Pure and Applied Chemistry attempts to provide a standard nomenclature for colloids as particles in a size range having a ...
Colloidal silicas exhibit particle densities in the range of 2.1 to 2.3 g/cm 3. Most colloidal silicas are prepared as monodisperse suspensions with particle sizes ranging from approximately 30 to 100 nm in diameter. Polydisperse suspensions can also be synthesized and have roughly the same limits in particle size.
Colloidal gold is a sol or colloidal suspension of nanoparticles of gold in a fluid, usually water. [1] The colloid is coloured usually either wine red (for spherical particles less than 100 nm) or blue-purple (for larger spherical particles or nanorods). [2]
A colloidal crystal is an ordered array of colloidal particles and fine grained materials analogous to a standard crystal whose repeating subunits are atoms or molecules. [1] A natural example of this phenomenon can be found in the gem opal , where spheres of silica assume a close-packed locally periodic structure under moderate compression .
This critical size range (or particle diameter) typically ranges from tens of angstroms (10 −10 m) to a few micrometres (10 −6 m). [ 7 ] Under certain chemical conditions (typically in base-catalyzed sols ), the particles may grow to sufficient size to become colloids , which are affected both by sedimentation and forces of gravity.
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