Magnesium compositional model

The goal of this research was to improve activity coefficient prediction, and hence, equilibrium calculations in flue gas desulfurization (FGD) processes of both low and high ionic strength. A data base and methods were developed to use the local composition model by Chen et al. (MIT/Aspen Technology). The model was used to predict solubilities in various multicomponent systems for gypsum, magnesium sulfite, calcium sulfite, calcium carbonate, and magnesium carbonate SCU vapor pressure over sulfite/ bisulfite solutions and, C02 vapor pressure over car-bonate/bicarbonate solutions. 

For this review the Earth s composition will be considered to be more similar to carbonaceous chondrites and somewhat less like the high-iron end-members of the ordinary or enstatite chondrites, especially with regard to the most abundant elements (iron, oxygen, silicon, and magnesium) and their ratios. However, before reaching any firm conclusions about this assumption, we need to develop a compositional model for the Earth that can be compared with different chondritic compositions. To do this we need to (i) classify the elements in terms of their properties in the nebula and the Earth and (2) establish the absolute abundances of the refractory and volatile elements in the mantle and bulk Earth. 

The comparative estimation of efficiency of zinc oxide and ZnCFO similar concentrations (3,0 5,0 7,0 phr) as the agents of metaloxide vulcanization system was carried out on example of modelling unfilled elastomeric compositions from chloroprene rubber of recipe, phr chloroprene rubber - 100,0 magnesium oxide - 7,0. Kinetic curves of rubber mixes curing process at 155°C are shown on fig. 8. The analysis of the submitted data testifies, that at increase of zinc oxide contents vulcanization kinetics is changed as follows the scorch time and optimum cure time are decreased, the cure rate is increase. Vulcanization... 

In order to facilitate calculations and increase the usefulness of the chemical model, the computerized model has been used to obtain simplified correlations suitable for hand calculations. These correlations predict equilibrium SO2 partial pressure and liquor composition as functions of liquor pH and the total dissolved concentrations of magnesium and chloride. 

The spring waters of the Sierra Nevada result from the attack of high C02 soil waters on typical igneous rocks and hence can be regarded as nearly ideal samples of a major water type. Their compositions are consistent with a model in which the primary rock-forming silicates are altered in a closed system to soil minerals plus a solution in steady-state equilibrium with these minerals. Isolation of Sierra waters from the solid alteration products followed by isothermal evaporation in equilibrium with the eartKs atmosphere should produce a highly alkaline Na-HCO.rCOA water a soda lake with calcium carbonate, magnesium hydroxy-silicate, and amorphous silica as precipitates. 

To experimentally validate the Gitterman model, we prepared an artificial seawater sample that had the composition of seawater s liquid partially frozen down to — 23 °C (Marion et al. 1999). To this sample we added an excess of mirabilite crystals to ensure an adequate sulfate source. The sample was then placed in a — 26 °C temperature-controlled bath and allowed to equilibrate with periodic sampling and analyses over a 12-week period. The precipitation of hydrohalite between — 23 °C and — 26 °C (Fig. 3.16) led to an initial decrease in the sodium molality. Magnesium, on the other hand, was conserved in the solution phase, as ice formed and hydrohalite precipi-... 

The difference between the compound energy model and the simple two-sublattice model can be illustrated with two ternary intermetallic phases from the Al-Mg-Zn system. One of these two phases is known to contain a constant composition of 54.5 atomic percent magnesium and an extended homogeneity range of aluminum and zinc, corresponding to the formula Mg6(Al,Zn)5. However, no crystallographic data is available for this phase. Therefore, it is appropriately thermodynamically modeled by two sublattices, in which one sublattice is exclusively occupied by Mg, while A1 and Zn are allowed to randomly mix on the second sublattice (Liang et al., 1998). 

The refractory condensate model has fallen out of favor, including with Lewis (1988). Nevertheless, it is a useful end-member case. Goettel (1988) calculated the composition of the silicate portion of an ultrarefractory Mercury (Table 2, column 2). This model composition contains no FeO or volatiles, and has large concentrations of the refractory elements—aluminum, calcium, and magnesium. We calculated the thorium and uranium contents of such refractory condensates by assuming chondritic Al/Th and Al/U ratios. A surface of this composition will contain many of the phases in calcium-aluminum-rich inclusions (CAls), such as forsterite, anorthite, spinel, perovskite, hibonite, and melilite. 

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