Salt bridges principle

Ah already stated the liquid junction potential results from the different mobility of ions. Consequently no diffusion potential can result at the junction of the electrolyte solution the ions of which migrate with the same velocity. It is just this principle on which the salt bridge, filled by solutions of those salts the ions of which have approximately the same mobilities, is based (the equivalent conductivities of ions Kf and Cl- at infinite dilution at 25 °C are 73.5 and 70.3 respectively and the conductivities of ions NH+ and NOg are 73.4 and 71.4 respectively). Because ions of these salts have approximately the same tendency to transfer their charge to the more diluted solution during diffusion, practically no electric double layer is formed and thus no diffusion potential either. The effect of the salt bridge on t he suppression of the diffusion potential will be better, the more concentrated the salt solution is with which it is filled because the ions of the salt are considerably in excess at the solution boundary and carry, therefore, almost exclusively the eleotric current across this boundary. 

In principle, a suitable reagent could convert pairs of associated side-chain groups such as salt bridges into stable covalent bonds. If there are distinct and distinguishable sets of associated groups representing two or... 

Table 8.3 lists a few representative standard electrode potentials (or reduction potentials). Figure 8.6 exemplifies the principle of an electrochemical cell. The hydrogen electrode is made up of a B-electrode (which does not participate directly in the reaction), which is covered by H2(g), which acts as a redox partner [H2(g) = 2H +2e ]. Pt acts as a catalyst for the reaction between H and H2(g) and acquires a potential characteristic of this reaction. The salt bridge between the two cells contains a concentrated solution of salt (such as KCl) and allows ionic species to diffuse into and out of the half-cells this permits each half-cell to remain electrically neutral. 

While in principle binding between proteins can be driven by widely varying mixtures of polar and electrostatic interactions (H-bonds and salt bridges),... 

Consider a situation in which zinc electrodes are put into two aqueous solutions of zinc sulfate at 0.10 M and 1.0 M concentrations. The two solutions are connected by a salt bridge, and the electrodes are joined by a piece of wire in an arrangement like that shown in Figure 19.1. According to Le Chatelier s principle, the tendency for the reduction... 

Analogous processes occur in inanimate systems. From elementary chemical principles it is known that when two metallic half-cells are coupled by a salt bridge, the direction and extent of the reaction between them can be determined from knowledge of the concentrations of the various components and the value of their standard electrode potentials. The more negative the standard electrode potential, the greater the reducing power of the half-cell. 

In principle any solid electrolyte having only one moving ion can be used to build an ion specific electrode. For this application the solid electrolyte is used as a separator between two reference electrodes (fig. U), One of these electrodes is in contact with a reference solution on one side of the solid membrane while the other reference electrode sees t he sample solution in which one wants to know the ion activity through a salt bridge. Excellent account of the theory of membrane potentials have been published (9) ... 

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