In chemistry, a suspension is a heterogeneous fluid containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than 1 micrometre.[1] The internal phase (solid) is dispersed throughout the external phase (fluid) through mechanical agitation, with the use of certain excipients or suspending agents. Unlike colloids, suspensions will eventually settle. An example of a suspension would be sand in water. The suspended particles are visible under a microscope and will settle over time if left undisturbed. This distinguishes a suspension from a colloid in which the suspended particles are smaller and do not settle.[2] Colloids and suspensions are different from a solution, in which the dissolved substance (solute) does not exist as a solid and solvent and solute two are homogeneously mixed.
A suspension of liquid droplets or fine solid particles in a gas is called an aerosol. In the atmosphere these consist of fine dust and soot particles, sea salt, biogenic and volcanogenic sulfates, nitrates, and cloud droplets.
Suspensions are classified on the basis of the dispersed phase and the dispersion medium, where the former is essentially solid while the latter may either be a solid, a liquid or a gas.
In modern chemical process industries, high shear mixing technology has been used to create many novel suspensions.
Common examples
- Mud or muddy water, is where soil, clay, or silt particles are suspended in water.
- Flour suspended in water, as pictured to the right.
- Paint
- Chalk powder suspended in water.
- Dust particles suspended in air.
- Algae in water
- Milk of Magnesia
See also
References
- ^ Chemistry: Matter and Its Changes, 4th Ed. by Brady, Senese, ISBN 0471215171
- ^ The Columbia Electronic Encyclopedia, 6th ed.
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