Aluminate equilibria

Analogously, pyrazolyl-aluminate and -indate ligands have been prepared <75JCS(D)749) and their chelating properties evaluated with cobalt, nickel, copper and zinc. Gallyl derivatives of pyrazoles and indazoles have been extensively studied by Storr and Trotter e.g. 75CJC2944) who determined several X-ray structures of these compounds. These derivatives exist in the solid state as dimers, such as (212) and (288). A NMR study in acetone solution showed the existence of a slow equilibrium between the dimer (212) and two identical tautomers (289) and (290) (Section 4.04.1.5.1) (81JOM(215)157). 

Researchers in the aluminium industry have investigated the solubility of goethite in sodium aluminate and NaOH solutions. Basu (1983) found, using samples of natural goethite, that the equilibrium solubility of goethite in sodium aluminate solution was close to zero at room temperature and increased exponentially as the temperature rose above 100 °C. She also found that the isothermal solubility was greater in 5 M NaOH than in 5 M sodium aluminate solution at 150 °C, for example, [Fej] was 20 and 50 mgL , respectively. 

It seems necessary at this time to emphasize that the above generalizations may pertain only as concerns O-H-N-O explosives and that diametrically opposed conclusions may apply to aluminized mixtures. Evidence is available that kinetic factors (which extend far beyond the time of the C-J condition), rather than thermodynamic factors, govern the extent of utilization of aluminum m the detonation. If, as seems reasonable, the rates of the aluminum reactions are highly temperature dependent, and if aluminum reacts at different rates with HaO, CO, and COa, detonation properties of aluminized explosives should depend very strongly on exact equilibrium compositions of these species in the C-J condition and in the early stages of the gas expansion. For such reasons, Eqs. (1) and (7) may be inapplicable for use with aluminized mixtures. 

Those chlorites associated with mixed layered clay minerals are most silica-rich and have the greatest compositional variations for grains in a single thin section they tend to be iron-rich and aluminous. One chlorite vein was found to transect a glauconite pellet. This chlorite was quite iron-poor indicating attainment of a local chemical equilibrium between chlorite and iron mica upon its crystallization. 

This possibility is due to the non-equivalence of Mg and Fe which segregate into corrensite and chlorite respectively. This effect is discussed in the chlorite chapter. Thus four major phyllosilicate phases could be present in an equilibrium situation. It should be noted that the expanding trioctahedral phase is or can be more aluminous than chlorite. This might lead one to think that some of the layers might in fact be dioctahedral such as those in sudoite. The importance of the differentiation of the two types of mixed layered minerals lies in the segregation of alumina and potassium in one (the dioctahedral mixed layered mineral)... 

When an expanding mineral is no longer stable, the iron content of the chlorite in equilibrium with illite will become more variable (Figure 49b). If chlorite is present due to a relatively high Fe/Fe + Mg content of a rock, it can occur with three other aluminous phases such as illite-montmorillonite and kaolinite. Thus the four-phase phyllosilicate assemblage common to argillaceous rocks can be accounted for by dividing the... 

Generally the first step is the preparation of the reaction mixture at low temperature (< 60°C). The different ingredients are mixed in this step, which in most cases results in the formation of the so-called synthesis gel. In this gel silicate and aluminate monomers and oligomers in solution are in equilibrium with condensed silicate and aluminate units in the gel phase. In some cases a digestion period is necessary to reach this equilibrium. 

Table 4.13 summarizes the calculated propulsion parameters for aluminized formulations in which the Al content has been varied in order to achieve an oxygen balance that is close to zero (with respect to C02, see eq. 2). Table 4.13 contains the corresponding values for a AP /Al formulation for comparison as well. Finally, Table 4.14 shows the calculated specific impulses for equilibrium expansion for the three optimized formulations (covalent 02N—02C—C02—N02 /Al, ionic [N0]2[02C C02] /Al and AP /Al). The results of Table 4.14 are graphically summarized in Figure 4.6. 

As with the aluminate phase, the average compositions take into account the requirement that these site occupancies should be reasonable from the standpoint of crystal chemistry. There is no basis for allocating cations to octahedral and tetrahedral sites separately as the preferences of some of the eations, especially Mg, in this structure are unknown, as is the temperature at which equilibrium is attained. This temperature probably varies between clinkers, and may be expected to affect the distribution. 

Several early phase equilibrium studies on systems of calcium silicates or aluminates with alkalis were reported (N9), but their significance needs to be reassessed because they postulated the existence of the compounds NCgAj or KC23Sj2, which in neither case is supported by more recent work. 

The applicability of these conclusions to production clinkers requires examination. The compositions of the aluminate and ferrite phases differ markedly from C3A and C4AF, respectively (Chapter 1) and, because of the presence of minor components, especially MgO, TiOj and alkalis, the compositions of the liquid phase differ from those in the pure system. We shall consider in turn first, whether glass is formed, and if so, under what conditions second, whether either C,2A2 or free lime crystallizes from the liquid phase under appropriate conditions and third, whether there is evidence of either equilibrium or independent cooling. 

The reason why mixes with AR > 1.7 do not yield any CjjA, on independent crystallization is that the solid phases are not pure CjA, QAF and CjS. For AR = 2.71, the quaternary liquid in equilibrium with C,S, C S and CjA at 1400X contains 55.7% CaO, 27.1% AljOj, 10.0% FcjOj and 7.2% SiOj (S8). This composition can be closely matched by a mixture of aluminate (63%), ferrite (30%) and belite (7%) with the normal compositions given in Table 1.2, the bulk composition of this mixture being 54.4% CaO, 26.4% AI2O3, 9.7% Fe Oj, 5.6% SiO and 1.8% MgO, with <1% each of TiOj, Mn20j, NajO and KjO. Independent crystallization can thus yield a mixture of the three phases. The liquid composition cannot be matched by a mixture of pure CjA, C AF and CjS, which is relatively too high in CaO, so that if no ionic substitutions occurred, some C,2A7 would also be formed. A strict comparison would be with the actual composition of the clinker liquid, which is modified by minor components, but lack of adequate data precludes this. 

Other than in their mean compositions. Slow cooling produces relatively large crystals of each phase, while fast cooling produces close intergrowths textures are discussed further in Section 4.2.1. Zoning occurs readily in the ferrite (Section 2.3.1), and may also occur in the aluminate. The distribution of atoms between octahedral and tetrahedral sites in the ferrite depends on the temperature at which internal equilibrium within the crystal has been achieved (Section 1.5.1). The degree of crystallinity of both phases appears to vary with cooling rate (V3). All these effects, and perhaps others, may affect the behaviour of the interstitial material on hydration. 

The Li partial pressures over different lithium silicates, aluminates, and molybdates are summarized by Ikeda et al. [163]. Li(g) is the most abundant species in the equilibrium vapor over these phases. 

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