Colloids general properties

One of the earliest known chemical properties of ferric salts was their ready conversion to ferric hydroxide colloids in solutions. These solutions were intensively studied in the classic period of colloid chemistry, and their properties have been discussed in detail by Weiser (8). Since the focus of these studies was on colloid properties per se, precautions were taken to prepare pure colloids. Generally hydrolyzed solutions would be dialyzed extensively against distilled water to remove foreign ions. Even the purest preparations retained detectable concentrations of anions, consistent with a positive surface charge on the colloidal particles. 

In order to understand the nature of radiocolloids, knowledge of the general properties of colloids is needed. Colloids are finely dispersed particles in a liquid phase, a gas phase or a solid. The size of colloidal particles is in the range between that of molecules or ions and that of particles visible by means of a light microscope, i.e. between about 1 nm and about 0.45 pm. The upper value corresponds to the mean wavelength of visible light. Large molecules, in particular polymers and biomolecules, approach or exceed the upper value and may also form colloids. 

The origin of the coagulation behavior of Iler s silica sols is far from understood. The electrosteric barrier model herein proposed is designed to stimulate new experimental initiatives in the study of colloidal silica sol particles and their surface structure. The adsorbed steric layer, impregnated with bound (exchanged) cations, at the surface of 1-100-nm-diameter silica sol particles has the general properties needed to understand the anomalous coagulation behavior. The details await experimental and theoretical input. 

General Properties of Liquid Solutions Solutions and Colloids Degree of Solubility Solubility and Equilibrium Solubility of Gases Henry s Law... 

In later chapters we shall discuss the properties of a variety of colloidal systems. However, as a preparation for our consideration of the general properties and stability of dispersions, it will be useful to use one simple example to outline some of their more important characteristics. It so happens that one of the first colloidal dispersions to have been examined systematically will suit our purpose admirably. 

In this case, the polymer chains have no conformational freedom. For the general properties of these films it is, therefore, unimportant, whether the objects are made out of polymer at all. Films made out of inorganic colloidal particles have the same general features. Because the properties are determined by friction between hard objects, attaching a hydrophihc head group to the polymer does not significantly change the properties [9, 10]. 

Properties of Colloidal Systems.—Colloidal solutions resemble true solutions in that they exert an osmotic pressure and have a lower freezing point than that of the solvent. Neither effect is as marked as in the true solution owing to the relatively greater size and smaller concentration of the dispersed particles. The osmotic pressure of the plasma proteins, however, is an important factor in maintaining the volume of blood, and in man has a normal value of 305-307 mm. HjO (0-03 atmospheres) at 22° C. In addition to these general properties, colloidal sj tems, especially suspensoids, exhibit special properties due to the surface and surface charge of the dispersed particles. These properties are —... 

In the simnlations of Hecht et al. [16], the simple coUisional coupling procedure described in Sect 7.1 was used. This means that the colloids were treated as point particles, and solvent particles could flow right through them. Hydrodynamic interactions were therefore only resolved in an average sense, which is acceptable for studies of the general properties of an ensemble of many colloids. The heat from viscous heating was removed using the stochastic thermostat described in Sect. 2.3. 

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