Stability field diagram

Figure 7. Tentative eH-pH stability field diagram for the system Hg-S-Cl-H O at 298 K. Activities of Cl and the dominant SO>, species are O.IM.

Fig. 10. Stability-field diagram (Na2O—AI2O3— SiO2— H2O).

This condition is represented as a plane on the mineral stability field diagram of Figure 6.12. As is obvious from the nature of reaction 6.26, the diagram predicts that the conditions favoring kaolinite formation and feldspar dissolution are low pH and low soluble and silica. 

Figure 7.8. Stability field diagram for soluble and solid forms of Mn under a range of redox potential and pH conditions, assuming a dissolved CO concentration of 10 M. Shaded areas delineate conditions that are unattainable because of water decomposition. (Adapted from W. Stumm and J. J. Morgan. 1981. Aquat/c Chemistry. 2nd ed. New York Wiley.)...

However, Stiibenetal. (1999) subsequently plotted stability field diagrams for Pt and Pd and showed that Pt is present in seawater dominantly as Pt(OH)2° and is close to saturation under seawater conditions. From this, it was argued that Pt is enriched in Co-rich cmsts mainly as a result of the preferential adsorption of Pt(OH)2° onto the surface of Mn and Fe oxy hydroxide minerals. Pd, on the other hand, lies at the boundary of the stability fields of PdCb and Pd(OH)2° and is probably undersaturated in seawater. Since PdCb can not be adsorbed on Mn oxy hydroxides which have a negative surface charge, this would explain the so-called negative Pd anomaly in marine manganese deposits. 

A system with two variables can be graphically illustrated either three-dimensionaUy or by projecting into a plane defined by axes on which the values of variables are plotted. So-called diagrams of predominating existence area (stability field diagrams) are obtained. 

Fig. 4. Stability field diagram for (R = rare earth. Sc or In) pyrochlores. A denotes high-...

Hem, j. D. 1961. Stability field diagrams as aids in iron chemistry studies. Journal of the American Water Works Association, 53, 211-229. 

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