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In chemistry, a suspension is a heterogeneous mixture containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than one micrometer.〔Chemistry: Matter and Its Changes, 4th Ed. by Brady, Senese, ISBN 0-471-21517-1〕 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.〔The Columbia Electronic Encyclopedia, 6th ed.〕 Colloids and suspensions are different from solutions, in which the dissolved substance (solute) does not exist as a solid, and solvent and solute are homogeneously mixed. A suspension of liquid droplets or fine solid particles in a gas is called an aerosol or particulate. 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. Suspensions are unstable from the thermodynamic point of view; however, they can be kinetically stable over a large period of time, which determines their shelf life. This time span needs to be measured to ensure the best product quality to the final consumer. “Dispersion stability refers to the ability of a dispersion to resist change in its properties over time.” D.J. McClements.〔(“Food emulsions, principles, practices and techniques” CRC Press 2005.2- M.P.C. Silvestre, E.A. Decker, McClements Food hydrocolloids 13 (1999) 419-424 )〕 ==Technique monitoring physical stability== Multiple light scattering coupled with vertical scanning is the most widely used technique to monitor the dispersion state of a product, hence identifying and quantifying destabilization phenomena.〔I. Roland, G. Piel, L. Delattre, B. Evrard International Journal of Pharmaceutics 263 (2003) 85-94〕〔C. Lemarchand, P. Couvreur, M. Besnard, D. Costantini, R. Gref, Pharmaceutical Research, 20-8 (2003) 1284-1292〕〔O. Mengual, G. Meunier, I. Cayre, K. Puech, P. Snabre, Colloids and Surfaces A: Physicochemical and Engineering Aspects 152 (1999) 111–123〕〔P. Bru, L. Brunel, H. Buron, I. Cayré, X. Ducarre, A. Fraux, O. Mengual, G. Meunier, A. de Sainte Marie and P. Snabre Particle sizing and characterization Ed T. Provder and J. Texter (2004)〕 It works on concentrated dispersions without dilution. When light is sent through the sample, it is back scattered by the particles. The backscattering intensity is directly proportional to the size and volume fraction of the dispersed phase. Therefore, local changes in concentration (sedimentation) and global changes in size (flocculation, aggregation) are detected and monitored. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Suspension (chemistry)」の詳細全文を読む スポンサード リンク
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