Donnan Dialysis

initial concentrations were different, counterdiffusion of equal amounts of Na + and K + through the membrane produced solutions with equal ratios of Na+ /K+ on both sides of the membrane at equilibrium. This relationship of concentrations of the ions in the solutions on opposite sides of the membrane is called the 'Donnan equilibrium'.

Before proceeding with the theory, it is useful to define some terms that are often used in discussions of modern polymeric ion-exchange membranes. First, an 'ion-exchange membrane' is a plastic film with fixed ionically charged groups dispersed more or less uniformly within the film. Associated with the fixed charges are mobile charges of opposite sign called 'counterions'. The counterions are free to exchange with other counterions in the adjacent solutions. When the membrane has fixed negative charges, e.g., sulfonic acid groups, it is called a 'cation-exchange membrane', and the counterions are cations. In the external solutions, mobile anions are associated with the cations, but in the membrane the charge balance is satisfied by the fixed negative charges. Therefore, anions tend to be excluded from the interior of the cation-exchange membrane. The ions with the same charge as the fixed charge in the membrane are called 'co-ions'.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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