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Colloid-Stability Qualitative Considerations

In a qualitative way, colloids are stable when they are electrically charged (we will not consider here the stability of hydrophilic colloids - gelatine, starch, proteins, macromolecules, biocolloids - where stability may be enhanced by steric arrangements and the affinity of organic functional groups to water). In a physical model of colloid stability particle repulsion due to electrostatic interaction is counteracted by attraction due to van der Waal interaction. The repulsion energy depends on the surface potential and its decrease in the diffuse part of the double layer the decay of the potential with distance is a function of the ionic strength (Fig. 3.2c and Fig. [Pg.251]

The van der Waal attraction energy, in a first approximation is inversely proportional to the square of the intercolloid distance. [Pg.252]

We will first illustrate how chemical variables affect surface charge and surface potential. Then we will discuss more quantitatively a physical stability model which depends on the surface potential (which, in turn, has been determined by chemical factors). [Pg.253]


The science of colloids appears to be entering upon a new stage, which is less empirical, and where the experimental study of better defined objects will be guided rather by more quantitative theories than by qualitative rules or working hypotheses , The theory of the stability of lyophobic colloids, as developed in this book, may serve as an example of this development. This stability problem has been placed on a firmer physical basis by the introduction of the concept of Van der Waals— London dispersion forces together with the theory of the electrolytic or electro-chemical double layer. In the present work, too, these theories form the starting points of our considerations. [Pg.208]

In this and the following chapters, we shall often be forced to restrict our considerations to double layers of the Gouy-Chapman type, neglecting the Stern correction Calculations on the interaction of SterN-Gouy layers are still scarce and incomplete, and further developments in this direction will have to be awaited before they can succcsfully be applied to the problem of the stability of hydrophobic colloids Fortunately, many salient points can be treated from the point of view of simple diffuse double layers and in more complicated cases it is often possible to take account of the influence of the STERN-Iayer in a qualitative or semi-quantitative way ... [Pg.248]


See other pages where Colloid-Stability Qualitative Considerations is mentioned: [Pg.251]    [Pg.837]    [Pg.837]    [Pg.839]    [Pg.841]    [Pg.251]    [Pg.837]    [Pg.837]    [Pg.839]    [Pg.841]    [Pg.62]    [Pg.212]    [Pg.139]    [Pg.73]    [Pg.121]   


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