Cl concentration

From an electrochemical viewpoint, stable pit growtli is maintained as long as tire local environment witliin tire pit keeps tire pit under active conditions. Thus, tire effective potential at tire pit base must be less anodic tlian tire passivation potential (U ) of tire metal in tire pit electrolyte. This may require tire presence of voltage-drop (IR-drop) elements. In tliis respect the most important factor appears to be tire fonnation of a salt film at tire pit base. (The salt film fonns because tire solubility limit of e.g. FeCl2 is exceeded in tire vicinity of tire dissolving surface in tlie highly Cl -concentrated electrolyte.)... 

CrNiMo stainless steels and Cr-rich special alloys Seawater (25°C) Cl" containing media <0.0 <-0.3 (in general more positive UfQ values determine) U becomes more negative with increasing Cl" concentration and temperature [4, 57-59]... 

Cl = concentration of chlorine in liquid, bottom of tower, lb mols/ft ... 

In chloride-containing solutions evolution of chlorine will also occur and is usually the predominant anodic reaction even at low Cl concentrations, e.g. brackish waters ... 

Consumption rates similar to those in artihcal seawater were reported for the Pb-20% Fe304 composites, which were found to give the optimum performance. However, in tap water with a high SO/" and COy concentration and low Cl concentration (36 ppm), consumption rates of 100 g A y were recorded. 

Table 2. Estimated cytoplasmic and extracytoplasmic K, Na and Cl concentrations in some eukaryotes...

The rates of oxidation of V by complexes of the type Co(NH3)sX, where X = H2O, NH3 and Cl , have been examined by Zwickel and Taube in H2O and in D2O solution. These workers have compared the results on such systems with data on the Cr +Co(NH3)6 reaction in H2O and D2O. The product unlike Cr, is substitution-labile. Consequently, a different approach is necessary for oxidations than is customary for Cr oxidations. The specific rate coefficients for Co(NH3)g and Co(NH3)6 " + Cr vary with Cl concentration according to... 

The HCl-treated AI2O3 was prepared at room temperature by adding 50 ml of aqueous HCl to AI2O3 such that the Cl" concentration was the same as in the catalyst preparation. After stirring the mixture vigorously for 1 h. Mg citrate was added, the mixture was stirred for another h, and then the solid was filtered, washed, dried, calcined, and activated in the same way as in the preparation of A11/AI2O3. 

ES in ore fluids is generally in a range of 10 -10 mol/kg H2O based on ES in present-day geothermal waters and fluid inclusion analytical data (Shikazono, 1972a). /ci- is represented as a function of ionic strength and temperature. Ionic strength is related to salinity which can be approximated as Cl concentration. Cl concentration can be estimated from fluid inclusion study. 

Cl concentration is similar to or higher than that of seawater. 

Several factors such as Cl concentration, water/rock ratio and temperature are important in controlling the chemical composition of the hydrothermal solution interacted with the rocks. For example, water/rock ratio affects the alteration mineralogy (Mottl and Holland, 1978 Seyfried and Mottl, 1982 Shikazono, 1984). For example, at low water/rock ratio, epidote is stable, while chlorite at high water/rock ratio (Shikazono, 1984 Shikazono and Kawahata, 1987). 

In Fig. 1.59 the relationship between temperature and concentration of elements (Zn, Ba) at constant Cl concentration which is equal to that of seawater obtained by the experimental studies and analytical data on natural hydrothermal solution (geothermal water) are shown. It is seen that the concentrations of base-metal elements (Zn, Fe, Mn, Cu, Pb) and Ba increase with increasing of temperature. Concentrations of these... 

Figure 1.56. Relationship between the zinc and Cl concentration in geothermal waters and hydrothermal solution experimentally interacted with rocks (Shikazono, 1988c).

There are different approaches to the study of hydrothermal alteration. For instance, Shikazono (1978a) showed the relationship between chemical composition of hydrothermal solution in equilibrium with the alteration minerals and Cl concentration in hydrothermal solution. 

It is thought from this reaction, that Au-rich electrum precipitates from ore fluids with high Cl concentration and low pH. Therefore, it is considered that different Cl concentration and pH are important factors causing different relationship between Ag content of electrum and Ag/Au total production ratio of Kuroko deposits and epithermal vein-type deposits. 

However, in order to clarify the depositional mechanism of electrum and sulfides, more detailed description of alteration minerals, 8 0, 8D data and the salinity (Cl concentration)-enthalpy relationship are clearly required, and the two fluids mixing model has to be evaluated based on these data. 

Previous studies clearly indicated that the chemical compositions of geothermal waters are intimately related both to the hydrothermal alteration mineral assemblages of country rocks and to temperature. Shikazono (1976, 1978a) used a logarithmie cation-Cl concentration diagram to interpret the concentrations of alkali and alkaline earth elements and pH of geothermal waters based on thermochemical equilibrium between hydrothermal solution and alteration minerals. 

This relationship is shown in Fig. 2.2 in which data on Na+ and Cl concentrations of geothermal waters in Japan and in other countries are plotted. 

The concentrations of Rb and Cs in feldspars in geothermal areas have not been studied. However, if the concentration ranges are similar to those observed for feldspars in common igneous rocks, we can construct curves to show the relationship of the concentration of an alkali element X+ and the Cl concentration of geothermal waters (Fig. 2.4 and Fig. 2.5). It is assumed that the concentrations of Cs and Rb in feldspars range from lO -" to 10 wt% and I0 to 10 wt%, respectively. 

Fig. 2.4. Relation between the Cs+ and Cl concentrations of geothermal waters. Solid lines 1 and 2 indicate the equilibrium condition between feldspars and solution, assuming that the Cs content of the feldspar is between 10 wt% and 10 wt%. For symbols used, see caption to Fig. 2.2 (Shikazono, 1978a).

Using the equilibrium constant for (2-5) and (2-9), the relationship between pH and Cl concentration can be derived as shown in Fig. 2.7. The line shown in Fig. 2.7 has a slope of approximately —1, indicating that the pH of the geothermal waters decreases with increasing Cl concentration. 

Combining the equilibrium relation for reaction (2-10) and the relationship between pH and the Cl concentration derived already, we can derive the dependence of... 

Ca + concentration on Cl concentration (Fig. 2.8). At constant temperature and activity of H2CO3, log(mca2+) plots linearly as a function of the logmci- with a slope of about +2. 

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