Properties of Colloidal Suspensions

It is by means of the ultramicroscope that the Brownian Movement may be observed. 

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In practice, sedimentation is an important property of colloidal suspensions. In fonnulated products, sedimentation tends to be a problem and some products are shipped in the fonn of weak gels, to prevent settling. On the other hand, in applications such as water clarification, a rapid sedimentation of impurities is desirable. 

Many properties of colloidal suspensions, such as their stability, rheology, and phase behaviour, are closely related to the interactions between the suspended particles. The background of the most important contributing factors to these interactions is discussed in this section. 

Klein R and D Aguanno B 1996 Scattering properties of colloidal suspensions Light Scattering, Principles and Development ed W Brown (Oxford Clarendon) pp 30-102... 

There have been other MPC dynamics studies of hydrodynamic effects on the transport properties of colloidal suspensions [61-64]. In addition, vesicles that can deform under flow have also been investigated using hybrid MPC-MD schemes [65-69]. 

Klein R. Static scattering properties of colloidal suspensions. In Brown W, ed. Light Scattering Principles and Development. Oxford Clarendon, 1996 30-102. 

Flow or deformation involves the relative motion of adjacent elements of the material. As a consequence such processes are sensitive to interatomic or intermolecular forces. In the case of liquids containing dispersed particles, interparticle forces are also important. Because the rheological properties of colloidal suspensions exhibit such a rich variety of phenomena, rheological studies not only provide information on medium-particle and particle-particle interactions but also arc of immense technological importance. 

The use of the Greek letter C (zeta) to denote the effective potential of the system is now universally accepted, and it is usually spoken of as the zeta potential. The zeta potential is very important in determining the properties of colloidal suspensions, as we shall now see. 

Many textbooks on the physicochemtca] properties of colloidal suspensions mention the phaimaceutical Held as one in udiich colloids find industrial and technological applications (see, c.g.. Refs. 1-3). Together with, perhaps, inks, food colloids, and paints, pharmaceutical suspensions are designed to be used in most cases not by specialists but ralher by petqile who only need lo know proper directions for use, and quick and efficient therapeutic effects. This means that in their formulation there are involved factors that are not normally considered when colloid scientists (nepare their suspensions. For instaiKe, pharmaceutical suspensions... 

Tirado, M.C., Arroyo, F.J., Delgado, A.V., and Grosse, C., Measurement of the low-frequency dielectric properties of colloidal suspensions comparison between different methods, J. Colloid Interface Sci., 227, 141, 2000. 

The interfacial properties of colloidal suspensions are determined by the chemical reactions (e.g. protonation) and adsorption of solutes. Additionally, the interface can be affected by the dissolution-precipitation equilibrium of the particle phase. This is because precipitation changes the surface morphology (Vigil et al. 1994) or leads to phase transition (Lefevre et al. 2002 Carrier et al. 2007). In addition, dissolution means degradation of the particles and may result in the loss of the finest particle fractions (i.e. Ostwald ripening). For this reason, it is necessary to understand the factors governing the dissolution of solid particles. 

As already stated in Chap. 3, there is a significant influence of particle interaction on the macroscopic properties of colloidal suspensions (e.g. viscosity, sedimentation, light scattering, sound propagation). Moreover, the attractive part of the particle interaction ultimately causes aggregation (or coagulation) in colloidal systems. 

The defined dispersion of particle agglomerates and aggregates is an indispensable step when studying the macroscopic properties of colloidal suspensions or measuring their state of dispersion. In that regard, there is a vast number of publications that provide experimental data on the dispersion of colloidal suspensions. However, only a few of them systematically investigate the main factors of dispersion processes as well as to which extent a scaling and comparison of dispersion processes is possible. Based on these publications, one can identify a set of parameters that determine the effectiveness of dispersion ... 

Rheological measurements are widely used to characterize the properties of colloidal suspensions (53,54). They can be used as a method of analysis as. 

Definition Aerosols are snspensions of solid or liquid particles in a gas. Dust, smoke, mists, fog, haze, and smog are various forms of common aerosols. Colloids are suspensions of solid particles in a liquid. Colloidal particles are typically in the range of nanometers to few microns. The rheological properties of colloidal suspensions are strongly affected by the donble-layer forces. Emulsions are suspensions of droplets of liquids in another immiscible liquid. 

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