Water, chemical interaction

In industry, cordierite is usually obtained by calcination of the mixtures containing talc, kaolinite and silica at 1300-1450°C for 20-60 h. The product contains the impurity phases spinel, mullite, clinoenstatite, etc., that worsen the exploitation characteristics of cordierite. Since the mentioned minerals contain structural water, chemical interaction between them during mechanical activation can be considered from the viewpoint of soft mechanochemical synthesis. Mechanical activation of this mixture does simplifies the interaction between its components. It is sufficient to heat this mixture for 2 h at a temperature of 1260°C to obtain practically homogeneous cordierite without impurity phases (Fig. 7.2) [2-9]. 

Physical phenomena of sodium-water reaction. Sodium-water chemical interaction proceeds in two stages at the first stage the reaction proceeds at a high rate with release of gaseous hydrogen and heat ... 

The two steps in the removal of a particle from the Hquid phase by the filter medium are the transport of the suspended particle to the surface of the medium and interaction with the surface to form a bond strong enough to withstand the hydraulic stresses imposed on it by the passage of water over the surface. The transport step is influenced by such physical factors as concentration of the suspension, medium particle size, medium particle-size distribution, temperature, flow rate, and flow time. These parameters have been considered in various empirical relationships that help predict filter performance based on physical factors only (8,9). Attention has also been placed on the interaction between the particles and the filter surface. The mechanisms postulated are based on adsorption (qv) or specific chemical interactions (10). 

While this chapter is mainly concerned with the chemical interactions between ocean and atmosphere, a few words need to be said about the physical interactions, because of their general importance for climate. The main physical interaction between the ocean and atmosphere occurs through the exchange of heat, water and momentum, although the presence of sea-ice acts to reduce all of these exchanges to a greater or lesser extent. 

The water derives from the chemical interaction of phos-... 

The dipole density profile p (z) indicates ordered dipoles in the adsorbate layer. The orientation is largely due to the anisotropy of the water-metal interaction potential, which favors configurations in which the oxygen atom is closer to the surface. Most quantum chemical calculations of water near metal surfaces to date predict a significant preference of oxygen-down configurations over hydrogen-down ones at zero electric field (e.g., [48,124,141-145]). The dipole orientation in the second layer is only weakly anisotropic (see also Fig. 7). 

Water-soluble initiators that can generate active free radicals are used in emulsion polymerization. The generation of active free radical can occur by two different mechanisms (1) thermal decomposition, and (2) chemical interaction. 

Although it is difficult to predict exactly which solute molecules will form clathrate solutions in any given host lattice, the general principle is quite clear. All molecules which fit into the cavities will be able to stabilize the host lattice, unless they show a specific chemical interaction with the solvent molecules. HC1 (or the other hydrogen halides), for instance, does not form a clathrate with water, but rather the stoichiometric compounds HC1 H20,... 

Deviations from Henry s law are exhibited by most gases having absorption coefficients greater than 100. In some cases the discrepancies vanish at higher temperatures. Thus Roscoe and Dittmar (1860) found that ammonia did not follow the law of Henry at the ordinary temperature, but Sims (1862) showed that the deviations from the law became less as the temperature at which absorption occurred increased, until at 100° the amount of ammonia dissolved by water was directly proportional to the pressure. The deviations appear to be always greatest under small pressures, and to decrease with increasing pressure, and therefore with increasing concentration of the solution they are doubtless due to chemical interaction between the solvent and dissolved gas. 

Release of water from the crystalline hydroxides (dehydroxylation) differs from the dehydration of a crystalline hydrate (Sect. 1) in that product release must be preceded by chemical interaction between anions. 

Chemical interactions also occur in the condensed phases. Some of these are expected to be quite complex, e.g., the reactions of free radicals on the surfaces of or within aerosol particles. Simpler sorts of interactions also exist. Perhaps the best understood is the acid-base relationship of NH3 with strong acids in aerosol particles and in liquid water (see Chapter 16). Often, the main strong acid in the atmosphere is H2SO4, and one may consider the nature of the system consisting of H2O (liquid), NH3, H2SO4, and CO2 under realistic atmospheric conditions. Carbon dioxide is not usually important to the acidity of atmospheric liquid water (Charlson and Rodhe, 1982) the dominant effects are due to NH3 and H2SO4. The sensitivity the pH of cloud (or rainwater produced from it) to NH3 and... 

Andreae, M. O. (1979). Arsenic speciation in seawater and interstitial waters the role of biological-chemical interactions on the chemistry of a trace element. Limnol. Oceanog. 24,440-452. 

Desorption of the organic molecules at potentials where is large is due to a phenomenon known in electrostatics In any charged electrostatic capacitor, forces are operative that tend (when this is possible) to replace a medium with a low e value with a medium with a higher s value. Therefore, regardless of any chemical interaction of the organic molecules with the surface, they are expelled electrostatically from the EDL at a certain value of Qs , and replaced by water molecules. 

The treatment of water-metal interactions deserves even more research. This is so because when a water molecule approaches a metal surface, two types of interactions can be envisaged. One of them is due to the polarization of the metal due to the partial charges that occur on the water molecule, and the other is due to overlap of the electronic clouds of the water molecules with the electronic cloud of the metal, called chemical interactions. For a water-Pt system, the latter predominate over the former, amounting to 90% of the total energy. 

The most important conclusion derived from the isotopic studies mentioned above is that isotopic characteristics of Kuroko ore fluids were caused dominantly by seawater-volcanic rock interaction at elevated temperature and by the mixing of seawater with small portions of igneous water or the hydrothermal solution whose chemical and isotopic compositions are controlled by water-rock interaction under the rock-dominated condition and also small proportion of mixing of meteoric water. 

In the last two decades, great progress has been made in the field of hydrothemal alteration studies, mainly from computation works on water-rock interactions at elevated temperatures (e.g., Wolery, 1978 Reed, 1983, 1997 Takeno, 1989). These studies revealed the relationship between the changes in chemical composition of hydrothermal solution and the relative abundance of minerals in the rocks. 

Giggenbach (1984) calculated the effect of temperature on the chemical composition of fluids buffered by alteration minerals. The causes for the hydrothermal alteration considered below are mainly based on the works by Shikazono (1978a) and Giggenbach (1984). The effect of the extent of water-rock interaction is not taken into account. 

Gamo, T. (1995) Wide variation of chemical characteristic of submarine hydrothermal fluids due to secondary modification processes after high temperature water-rock interaction, a review. In Sakai, H. and Nozaki, Y. (eds.), Biogeochemical Processes and Ocean Flux in the Western Pacific, Terra Sci. Publ., pp. 425-451. 

Chemical compositions of major elements (alkali, alkali earth elements. Si) in back-arc and midoceanic ridge hydrothermal solutions are not so different (Table 2.15). This is thought to be due to the effect of water-rock interaction. For example, Berndt et al. (1989) have shown that mQ i+ of midoceanic ridge hydrothermal fluids is controlled by anorthite-epidote equilibrium (Fig. 2.37). Figure 2.37 shows that /Mca2+/m + of back-arc hydrothermal fluids is also controlled by this equilibrium. 

These differences are considered to be attributed to the dilferences in compositions of rocks and alteration minerals interacted with circulating seawater or modified seawater at elevated temperatures. For example, high K and Li concentrations in the hydrothermal solution in the Mid-Okinawa Trough baek-arc basin (Jade site) are due to the interaction of hydrothermal solution with acidic volcanic rocks (Sakai et al., 1990). It is evident that the chemical compositions of hydrothermal solution are largely alfected by water-rock interaction at elevated temperatures. 

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