Colloidal system: Difference between revisions
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<div class="definition"><div class="short_definition">( | <div class="definition"><div class="short_definition">(''Also called'' colloidal dispersion, colloidal suspension.) An intimate mixture of two substances, one of which, called the dispersed phase (or colloid), is uniformly distributed in a finely divided state through the second substance, called the dispersion medium (or dispersing medium).</div><br/> <div class="paragraph">The dispersion medium may be a gas, a liquid, or a solid and the dispersed phase may also be any of these, with the exception of one gas in another. A system of liquid or solid [[particles]] colloidally dispersed in a gas is called an [[aerosol]]. A system of solid substance or water-insoluble liquid colloidally dispersed in liquid water is called a [[hydrosol]]. There is no sharp line of demarcation between true solutions and colloidal systems or between mere suspensions and colloidal systems. When the particles of the dispersed phase are smaller than about 10<sup>-3</sup> μm in diameter, the system begins to assume the properties of a true solution; when the particles dispersed are much greater than 1 μm, separation of the dispersed phase from the dispersing medium becomes so rapid that the system is best regarded as a [[suspension]]. According to the latter criterion, natural clouds in the [[atmosphere]] should not be termed aerosols; however, since many [[cloud]] forms apparently exhibit characteristics of true colloidal suspensions, this strict physico-chemical definition is often disregarded for purposes of convenient and helpful analogy. [[condensation nucleus|Condensation nuclei]] and many artificial [[smokes]] may be regarded as aerosols.</div><br/> </div> | ||
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Latest revision as of 15:40, 25 April 2012
colloidal system
(Also called colloidal dispersion, colloidal suspension.) An intimate mixture of two substances, one of which, called the dispersed phase (or colloid), is uniformly distributed in a finely divided state through the second substance, called the dispersion medium (or dispersing medium).
The dispersion medium may be a gas, a liquid, or a solid and the dispersed phase may also be any of these, with the exception of one gas in another. A system of liquid or solid particles colloidally dispersed in a gas is called an aerosol. A system of solid substance or water-insoluble liquid colloidally dispersed in liquid water is called a hydrosol. There is no sharp line of demarcation between true solutions and colloidal systems or between mere suspensions and colloidal systems. When the particles of the dispersed phase are smaller than about 10-3 μm in diameter, the system begins to assume the properties of a true solution; when the particles dispersed are much greater than 1 μm, separation of the dispersed phase from the dispersing medium becomes so rapid that the system is best regarded as a suspension. According to the latter criterion, natural clouds in the atmosphere should not be termed aerosols; however, since many cloud forms apparently exhibit characteristics of true colloidal suspensions, this strict physico-chemical definition is often disregarded for purposes of convenient and helpful analogy. Condensation nuclei and many artificial smokes may be regarded as aerosols.
