S System

Let us now include an additional component to the Fe-0 system considered above, for instance S, which is of relevance for oxidation of FeS and for hot corrosion of Fe. In the Fe-S-0 system iron sulfides and sulfates must be taken into consideration in addition to the iron oxides and pure iron. The number of components C is now 3 and the Gibbs phase rule reads Ph + F = C + 2 = 5, and we may have a maximum of four condensed phases in equilibrium with the gas phase. A two-dimensional illustration of the heterogeneous phase equilibria between the pure condensed phases and the gas phase thus requires that we remove one degree of... 

As indicated above, rather than keeping the temperature constant, we can replace the partial pressure of one of the gas components with the temperature as a variable. Figure 4.26 is a diagram of the Fe-S-0 system in which In pQi is plotted versus temperature. Here psq2 is fixed in order to allow a two-dimensional representation. 

C104) crystallizes in 96% yield in a second-order asymmetric manner. The solution actually contains the equilibrium mixture A(jR) A(jR) = 7 3.1036 Both Co2, and OH- effect rapid mutarota-tion about the metal in this complex but not about the chiral carbon. With (S)-penicillamine a similar equilibrium obtains (A A[Co (S)pen (en)2]2+ = 7 3) but preferential crystallization does not occur.1037 X-Ray structures confirm equatorial and axial dangling carboxylate functions in A-[Co (R)cys (en)2](C104) and A-[Co (7 )cy s (en)2 ] (C104) H2 O respectively.1037 (N,S) bonding seems to be preferred in (N,S,0) systems (cysteine, penicillamine) but (N,0)[Co (R)cys (en)2]2+ has been prepared by reduction of the tridentate sulfenamide complex (285 equation 159).1038 This (N.O) chelate lacks the extended charge transfer absorptions in the near UV characteristic of thiolate coordination. 

Fig. 19. Schematics of possible exchanges in M P-TCNE leading to monomer or trimer S = 1/2 and dimer S = 0 systems...

For some applications, different coordinate axes become more convenient for the construction of stability diagrams. For example, the phase equilibria for the Ni-S-0 system in Figure 2.8 may be equally well represented on a plot of logpo2 versus logpsos since specification of these two variables fixes logp because of the equilibrium shown in Equation (2.40) ... 

The corrosion of alloys in gases containing mixed oxidants is a problem of major interest. The proper thermodynamic treatment of this type of problem requires a combination of the concepts presented in Sections (d) and (e). This is a difficult task and a lack of experimental data for ternary compounds has prevented significant calculations of this type. One exception is the work of Giggins and Pettit in which a simplified three-dimensional diagram (log versus log poj versus log acr) has been constructed for the Ni-Cr-S-0 system. 

In these equations a a is the activity of A, and ua o and aA s are the activities of the oxide and sulphide, respectively. If it is assumed that the oxide and sulphide are immiscible, then the oxide and sulphide activities can be taken to be unity for the A-S-0 system. Similarly, at the metal-scale interface the metal activity will be unity but it will fall throughout the scale towards the scale-gas interface. 

Above 600 °C, the formation of a eutectic liquid in the Ni-S-0 system at the metal-scale interface gives rise to grain-boundary penetration of the metal, as shown... 

Shift the time axis by the maintenance time CAS = CAS + y(i). Element state L(j) change to Lg) = 0 the element is serviceable. System state S change to S = 0 system is non-functional. 

Reaction equiUbria for these reactions are controlled by the partial pressures of oxygen and sulfur dioxide, and can be simply explained by reference to the phase diagram for the Pb-S-0 system as... 

Since the original bag model calculations of the H particle mass by Jaffe, the properties of this state have been analyzed in a variety of calculations such as quark potential models and lattice gauge calculations. Fig. III.A. 1 shows a comparison of known baryon masses with the mass of the H as predicted in different types of models. At the left are various mass pairs with the AA being the lowest S = -2, B = 2 system but substantially more massive than several of the S = -1 and S = 0 systems. 

Sulfur derivatives behave in a manner similar to phosphorous compounds. This section considers the S—H stretch (I), the C—S (II, A) and S—S (II, B) stretches, and the S=0 stretch (III). The latter system (S=0 stretch) is examined in detail because considerable information about the local environment of the S=0 system can be extracted from the vibrational spectra. The data cover sulfoxides, sulfmic esters, and sulfites (III, C) plus sulfones, sulfonates, and sulfates and the influence of halogen and nitrogen substitution on these systems. (Ill, D). Finally C=S, C S and S—S stretches are briefly considered. 

Phase stability diagram for Na-V-S-0 system at 900°C (Hwang and Rapp, 1989). 

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