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How are the colloidal solutions classified on the basis of physical states of the dispersed phase and dispersion medium?

How are the colloidal solutions classified on the basis of physical states of the dispersed phase and dispersion medium?

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Suraj Prasad IIT Patna
askIITians Faculty 286 Points
9 years ago
Because the size of the dispersed phase may be difficult to measure, and because colloids have the appearance of solutions, colloids are sometimes identified and characterized by their physico-chemical and transport properties. For example, if a colloid consists of a solid phase dispersed in a liquid, the solid particles will not diffuse through a membrane, whereas with a true solution the dissolved ions or molecules will diffuse through a membrane. Because of the size exclusion, the colloidal particles are unable to pass through the pores of an ultrafiltration membrane with a size smaller than their own dimension. The smaller the size of the pore of the ultrafiltration membrane, the lower the concentration of the dispersed colloidal particles remaining in the ultrafiltered liquid. The measured value of the concentration of a truly dissolved species will thus depend on the experimental conditions applied to separate it from the colloidal particles also dispersed in the liquid. This is particularly important for solubility studies of readily hydrolyzed species such as Al, Eu, Am, Cm, or organic matter complexing these species. Colloids can be classified as follows:

Medium/phase Dispersed phase
Gas Liquid Solid
Dispersion
medium Gas None
All gases are miscible and thus do not form colloids Liquid aerosol
Examples: fog, hair sprays Solid aerosol
Examples: smoke, ice cloud, atmospheric particulate matter
Liquid Foam
Example: whipped cream, shaving cream Emulsion
Examples: milk, mayonnaise, hand cream Sol
Examples: pigmented ink, blood
Solid Solid foam
Examples: aerogel, styrofoam, pumice Gel
Examples: agar, gelatin, jelly Solid sol
Example: cranberry glass

Based on the nature of interaction between the dispersed phase and the dispersion medium, colloids can be classified as: Hydrophilic colloids: These are water-loving colloids.The colloid particles are attracted toward water. They are also called reversible sols. Hydrophobic colloids: These are opposite in nature to hydrophilic colloids. The colloid particles are repelled by water. They are also called irreversible sols.

In some cases, a colloid can be considered a homogeneous mixture. This is because the distinction between "dissolved" and "particulate" matter can be sometimes a matter of approach, which affects whether or not it is homogeneous or heterogeneous.

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