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Dissolution of small crystals or sol particles and the redeposition of the dissolved species on the surfaces of larger crystals or sol particles was first described by Wilhelm Ostwald in 1896. [4] [5] For colloidal systems, Ostwald ripening is also found in water-in-oil emulsions, while flocculation is found in oil-in-water emulsions. [6]
The magnitude of the equilibrium constant depends on the Gibbs free energy change for the reaction. [2] So, when the free energy change is large (more than about 30 kJ mol −1), the equilibrium constant is large (log K > 3) and the concentrations of the reactants at equilibrium are very small. Such a reaction is sometimes considered to be an ...
When lyophilic sols are added to lyophobic sols, depending on their sizes, either lyophobic sol is adsorbed in the surface of lyophilic sol or lyophilic sol is adsorbed on the surface of lyophobic sol. The layer of the protective colloid prevents direct collision between the hydrophobic colloidal particles and thus prevents coagulation. [1]
Particle agglomeration can be a reversible or irreversible process. Particle agglomerates defined as "hard agglomerates" are more difficult to redisperse to the initial single particles. In the course of agglomeration, the agglomerates will grow in size, and as a consequence they may settle to the bottom of the container, which is referred to ...
The peptization of a liquid mixture is the process of converting the mixture into a colloid by shaking it with a suitable electrolyte called a peptizing agent. [1] That is, the insoluble solid particles which have settled out of the mixture (i.e. the precipitate) are reformed into microscopic particles suspended in the mixture.
The molecules in a drop of food coloring added to water will eventually disperse throughout the entire medium, where the effects of molecular diffusion are more evident. However, stirring the mixture with a spoon will create turbulent flows in the water that accelerate the process of dispersion through convection-dominated dispersion.
However, the mobility of inorganic colloids is very low in compacted bentonites and in deep clay formations [4] because of the process of ultrafiltration occurring in dense clay membrane. [5] The question is less clear for small organic colloids often mixed in porewater with truly dissolved organic molecules.
The coagulation of gold sol results in an increase in particle size, indicated by a colour change from red to blue or purple. The higher the gold number, the lower the protective power of the colloid, because a greater amount of colloid is required to prevent coagulation. The gold number of some colloids are given below.