Calcareous minerals

Calcareous minerals and evaporite minerals (haUdes, gypsum) are very soluble and dissolve rapidly and, in general, congmendy, ie, yielding upon dissolution the same stoichiometric proportions in the solution as the proportions in the dissolving mineral and without forming new soHd phases (Fig. 

Calcareous minerals such as gypsum [13397-24-5] when added in stoichiometric amounts relative to the barite impurities, reduce acid-soluble barium losses (16). 

Mineralized coal impure coal that is heavily impregnated with mineral matter, either dispersed or discretely localized along cleat joints or other fissures pyrite and calcareous minerals are the most common (ASTM D-2796). 

The Effect of Adsorption on the Levels of Surfactant in Injection Fluids -- From the results of Figures 4 and 5 it is possible to assess the changes in the concentration of surfactant as a consequence of its adsorption on the minerals forming the reservoir. The results reported in this paper are for quartz, silica, or glass nevertheless, these solids probably represent the worst cases, because the adsorption of nonionics on alumina (and by extension onto alumino silicates) and on calcareous minerals is lower than the adsorption onto quartziferous materials (G. Gonzalez, A. Travalloni, in progress). 

These different states were based on Black s 1756 article in Essays and Reviews. To help his reader, Anderson offered his own nine variety arrangement of mild calcareous earth (since the caustic and effete were not stable).37 For each variety, he took care to note two classification characters purity and hardness. Purity referred to the percentage of mild calcareous earth contained in the stones, something that could be visually inferred from the stone s transparency. Hardness referred to how much the stone had been able to crystallize - a process in which saline substances, when dissolved in water, and put into proper circumstances for that purpose, separate from the water, and shoot into regular figures, which assume different forms, and are more or less transparent according to the different nature of the salt, as nitre, alum, c. 38 After setting out this classification, Anderson then proceeded to explain how chemistry could be used to find and assay calcareous minerals. 

The net result of these reactions is that 4 moles of pyrite are oxidized to produce 4 moles of Fe(OH)3 sj, which causes the yellow-brown discoloration of the water 12 moles of H+ (strong acid) are produced which then react with calcareous minerals in the soil to give rise to waters that have a high hardness and high total dissolved solids content. Another reaction of importance in acid mine drainage is the oxidation of FeS2(s) ferric iron (Fe ). Stoichiometrically, this reaction is... 

DTA can be applied to identify and estimate various t)q)es of clays and calcareous minerals (Fig. l). These minerals can be differentiated by determining the temperature at which the endothermic and exothermic peaks occur. For example, kaolinites exhibit an endothermic peak at... 

Mercury ore deposits occur in faulted and fractured rocks, such as limestone, calcareous shales, sandstones, serpentine, chert, andesite, basalt, and rhyolite. Deposits are mostiy epithermal in character, ie, minerals were deposited by rising warm solutions at comparatively shallow depths from 1—1000 m (6). 

Clays composed of mixtures of clay minerals having from 20—50% of unsorted fine-grain nonclay materials are most satisfactory. Large amounts of iron, alkaHes, and alkaline earths, either in the clay minerals or as other constituents, cause too much shrinkage and greatiy reduce the vitrification range thus, a clay with a substantial amount of calcareous material is not desirable. Face bricks, which are of superior quaHty, are made from similar materials but it is even more desirable to avoid these detrimental components (see Building materials, survey). 

Dissolution of CaCOs is a congruent reaction the entire mineral is weathered and results completely in soluble products. The above reaction is driven to the right by an increase of CO2 partial pressure and by the removal of the Ca and/or bicarbonate. Any impurities present in the calcareous rock, such as silicates, oxides, organic compounds, and others, are left as residue. As the calcium and bicarbonate leach... 

Most primary and secondary minerals found in soil systems are barely soluble in the soil solution. The amount of mass from the bulk phase to hydrated ions in soil solution is negligible compared to the total mass of the solid phase. In arid and semi-arid soils, concentrations of most trace metals in soil solution may be controlled by their carbonates and to some extent by their hydroxides. Other than carbonates, trace elements in arid and semi-arid soils may also occur as sulfate, phosphate or siliceous compounds, or as a minor component adsorbed on the surface of various solid phase components. The solubility of carbonates, sulfates and other common minerals of trace elements in arid and semi-arid soils will be discussed in Chapter 5. Badawy et al. (2002) reported that in near neutral and alkaline soils representative of alluvial, desertic and calcareous soils of Egypt, the measured Pb2+ activities were undersaturated with regard to the solubility of... 

In arid and semi-arid soils, calcite, dolomite, leonhardite (Ca2Al4Si8024.7H20) and lawsonite (CaAl2Si208.2H20) can be possible minerals. Calcium carbonate strongly influences soil properties in arid and semi-arid soils. Most calcareous soils have soil a pH in the range of 7.3-8 5. When sodium is predominant in soils, soil pH is above 8.5. In most arid and semi-arid soils, calcium carbonates (calcite and dolomite) generally accumulate and are most likely to control the Ca2+ and Mg2+ solubility in these soils (Lindsay, 1979). 

Trace elements can be precipitated as carbonates, sulfates, phosphates and hydroxides in arid and semi-arid environments. But most carbonates are more stable in arid and semi-arid soils than other solid phases. Cadmium hydroxide (Cd(OH)2), sulfate (CdS04) and phosphates (Cd3(P04)2) are more soluble than carbonate (CdC03, octavite), therefore the former minerals are not stable in arid soils. In calcareous soils, CdC03 (octavite) is the main Cd mineral to control Cd2+ activity in soil solution. At high C02... 

The protocol involving NaOAc-HOAc at pH 5 was first proposed and used by Jackson (1958) to remove carbonates from calcareous soils to analyze soil cation exchange characteristics (Grossman and Millet, 1961). Other researchers used HOAc for the extraction of metals from sediments and soils (Nissenbaum, 1972 Mclaren and Crawford, 1973). Tessier et al. (1979) first used the NaOAc-HOAc solution at pH 5 to dissolve the carbonate fraction from sediments. Since then, the NaOAc-HOAc buffer has been widely used as a specific extractant for the carbonate phase in various media (Tessier et al., 1979 Hickey and Kittrick, 1984 Rapin et al., 1986 Mahan et al., 1987 Han et al., 1992 Clevenger, 1990 Banin et al., 1990). Despite its widespread use, this step is not free from difficulties, and further optimization is required in its application. Questions arise with regard to this step in the elemental extraction from noncalcareous soils, the dissolution capacity and dissolution rates imposed by the buffer at various pHs, and the possibility that different carbonate minerals may require different extraction protocols (Grossman and Millet, 1961 Tessier et al., 1979). 

Ladd JN, Amato M, Parsons JW (1977) Studies of nitrogen immobilization and mineralization in calcareous soils. 111. Concentration and distribution of nitrogen derived from soil biomass. In Soil organic matter studies, vol 1. International Atomic Energy Agency, Vienna, pp 301-311... 

The processes described and their kinetics is of importance in the accumulation of trace metals by calcite in sediments and lakes (Delaney and Boyle, 1987) but also of relevance in the transport and retention of trace metals in calcareous aquifers. Fuller and Davis (1987) investigated the sorption by calcareous aquifer sand they found that after 24 hours the rate of Cd2+ sorption was constant and controlled by the rate of surface precipitation. Clean grains of primary minerals, e.g., quartz and alumino silicates, sorbed less Cd2+ than grains which had surface patches of secondary minerals, e.g., carbonates, iron and manganese oxides. Fig. 6.11 gives data (time sequence) on electron spin resonance spectra of Mn2+ on FeC03(s). 

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