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Chapter 20

Dispersion Stability

The stability of a dispersion depends on the electrostatic repulsion between particles, as calculated by double-layer theory, being strong to keep them sufficiently apart to weaken their mutual attraction as calculated by dispersion-force theory. Electrostatic stability is greatest where ionic strength is lowest and is reduced as the ionic strength is raised. DLVO theory attacked that matter and succeeded in finding a rationale for the empirical Schulze-Hardy rule, which had observed that the coagulating power of ions, as measured inversely by their effective concentrations, increased approximately in the proportion 1000:100:1 for uni-, bi-, and trivalent ions. In solvents of low dielectric constant, the low concentration of counter-charges and the long range of Coulombic repulsion makes electrostatic stability very effective and free from the vulnerability of aqueous systems

Key Words: complex ion, critical coagulation concentration (CCC), DLVO theory, electrocratic, Fick’s law, half-life, ionic strength, lyocratic, lyophilic, lyophobic, Schulze-Hardy rule, secondary minimum, slow coagulation, stability ratio, surface potential, zeta potential









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