The V E-pH Diagram

The equations in the previous paragraph may be treated with the Nernst equation to arrive at the calculated values of E at which the changes in predominant species occur. The values estimated from the diagram as given above are shown in brackets. 

The first three equations above lend themselves to treatment by equilibria expressions and the last two by the Nernst expression. In all five cases it is the pH that is being solved for. The estimated values taken from the E-pH diagram are presented in brackets for comparison. 

At this juncture, four different E-pH diagrams have been empiricaiiy examined in detaii. Severai important points are to be noted. First, an E-pH diagram shows the regions of species predominance under conditions of E and pH. Second, the regions of predominance are separated by iines which show the transformations of predominant species. Third, these iines are reflections of transformation reactions which can be represented by equations. Fourth, when the transformation equation does not show the hydrogen ion, the 

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