Predominance area diagrams

Fig. 7.75 Superimposed predominance area diagrams at 950 K for the Co-S-O system (solid lines) and the Cu-S-O system (broken lines). Within the area/I, C0SO4 and CuO are the stable...

A standard approach for the theoretical presentation of electrochemical equilibria is the use of Pourbaix, or potential-pH predominance area diagrams, which incorporate chemical and electrochemical thermodynamics simultaneously in a straightforward manner. These diagrams comprise an extremely useful, yet fundamental,... 

Figure 5. A predominance area diagram for the Cu-Cl -H20-H -e system at 298.15 K analogous to a pH-pE diagram but in which log(10)a(Cl ) replaces pH as a variable. The pH is less than 5. The activity of the predominant copper solution species are 10 e.

Porterfield. W. W., 295 Positive oxidation states, halogens in, 837-848 Posttransition metals, 28. 876 Potassium, 309, 582-587 Potentials, electrode, 378-383 Pourbaix diagram, 591-592 Praseo complex, 388,491, 493 Predominance area diagram, 591 Prewitt, C. T., 116-117 Principal axis, 51 Prism, trigonal prism, 489-491 Probability function, 13 Prosthetic group, 919 Proteins, and blue copper proteins, 912-916 Proton... 

Figure 2. Predominance area diagram of the ternary system Cu2+-H20-C02 (25° C1 = 0)...

Construct a predominance-area diagram for calmagite and zinc ions, given that log K for the zinc calmagite complex is 12.5 and that the solubility product of zinc hydroxide is 5 x 10 . ... 

Figure 9.3-5 is a Pourbaix. predominant-area, diagram for the S-O-HjO system for a total activity of all dissolved sulftir species of 10 1 ( S — 10" ). The only stable sulfiir species are HSOJ. SO2-. H.S. HS". and elemental sulfur. The formation of elemental sulftir films occurs in acid solutions as indicated. In basic solution, during the oxidation of sulfur-bearing compounds, intermediate metastabte solfor species such as thiosulfate, dithionate. and polythionates form. This is a problem previously described in the Sherrill Gordon process. Under acid conditions, during the dissolution of sulfide minerals, elemental sulfur layers often form but metastable solfor intermediates such as thiosulfate and sulfite are not observed. 

Fig. 7.3 Predominance area diagram for the system Zn-O-C. The line for the Boudouard equilibrium crosses the coexistence line for ZnO/Zn (gas) at the point A at unit pressures of CO and Zn (gas). When 7" > then ZnO can be reduced to Zn using solid carbon.

ZHO/BEZ] Zhorov, V. A., Bezborodov, A. A., Popov, N. I., Predominance-area diagrams and equilibrium ratios of inorganic forms of cobalt and nickel in ocean water. Oceanology, 16, (1976), 463-466. Cited on pages 224, 442. 

Predominance Area Diagrams. To present the equilibria in Eqs. 6-20 to 6-25 on a pC-pH diagram, it was necessary to fix the total carbonate concentration. In the second type of diagram— the predominance area diagram— we can show the effect of Ct.coj and pH on the predominant Fe(II) species. This diagram only shows the predominant species at any particular pH, however—not the concentration of each soluble species. To sketch such a diagram, it is necessary to fix the maximum total... 

We will state these equations and draw the lines they represent on a pCt.coj- pH predominance area diagram then by deduction we will select the areas of predominance for each species. Our approach will be to first examine the equilibria between Fe " " and the various hydroxo complexes, since these are independent of Cx.cog and will allow the establishment of pH regions of the predominance of the various hydroxo species. The task of deciding where to draw the lines that describe boundaries between hydroxo species and FeCOgts) will then be made easier. Selection of the first relationship to plot is arbitrary in this case we begin with Fe(OH)2(s) - Fe(OH)g-,... 

In this section we will first present the development of a simple diagram (the so-called pe-pC or E -pC diagram) for a reaction that involves only electron transfer in a homogeneous system. Next we will consider the predominance area diagrams for presenting combined redox and acid-base equilibria. Finally, we will add a third dimension and consider systems with multiple phases using the pe-pH predominance area diagram. 

For example, let us consider such a predominance area diagram for aqueous bromine species at 25° in which the diagram axes are pH and the negative log of the bromide concentration. 

Fig. 7-5. Predominance area diagram for aqueous bromine species at 25 C.

Fig. 7-6. Predominance area diagrams for aqueous chlorine and aqueous iodine at 25 C. (a) Aqueous chlorine and (b) aqueous iodine. After D. G. Taylor and J, D. Johnson, chapter in Chemistry oi Water Supply, Treatment and Distribution, A. J. Rubin, ed, Ann Arbor Science, 1974. Reprinted by permission of Ann Arbor Science Publishers, Inc, Mich.

Figure 7.6 Metal-sulphur-oxygen stability or predominance area diagram.

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