Dissolution potential, definition

There is, however, a definite difference in the electrode potential between the photoexcited rc-type electrode and the p-type electrode of the same semiconductor. The electrode potential of the former is less positive than that of the latter by a magnitude nearly equal to Ae = n P p P, which is the difference between the flat band potential of the n-type and that of the p-type. The anodic dissolution of the photoexcited w-type semiconductor electrode, as a result, will occur in the potential range less positive by about Ae than that for the p-type electrode of the same semiconductor. Figure 22.10 shows schematic polarization curves of the anodic hole emitting dissolution with an n-type electrode and with a p-type electrode of the same semiconductor under the dark and photoexcitation conditions. Such photoexcited dissolution was observed with w-type GaAs electrodes [14,15],... 

It has been found that about 15% of the total anodic dissolution current is consumed locally by hydrogen evolution in A1 pits and crevices [65, 66]. This means that the current measured at an applied potential is only a fraction of the true anodic dissolution current. Finally, the determination of pit growth kinetics at open circuit is a challenge, because by definition, no net current is passed at open circuit. 

Experimental measurements of solubility are influenced by many different factors, including the purity of the solute and solvent, presence of cosolvents, presence of salts, temperature, physical form of the undissolved solute, ionization state, and solution pH [18]. Consequently many different definitions of solubility are in common use in the published literature. Here we discuss the intrinsic aqueous solubility, Sg, which is defined as the concentration of the neutral form of the molecule in saturated aqueous solution at thermodynamic equilibrium at a given tanperature [18-20]. Intrinsic aqueous solubility is used to calculate dissolution rate and pH-dependent solubility in models such as the Noyes-Whimey equation [21] and the Henderson-Hasselbalch equation [22, 23], respectively. Prediction of the intrinsic aqueous solubility of bioactive molecules is of great importance in the biochemical sciences because it is a key determinant in the bioavailability of novel pharmaceuticals [1, 3, 24-26] and the environmental fate of potential pollutants [27, 28],... 

Although there is no external current, anodic and cathodic processes can still occur at sites on the interface between solid and aqueous solution because of the electrolytic conductance of the corrosive medium. At electrochemical equilibrium, this leads to a definite jump in the electrical potential at the phase boundary. Kinetic barriers to certain partial reaction steps of the electrochemical process can cause the potential to be displaced from its equilibrium value. Thus, for example, instead of a dissolution of metal ... 

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