Primary mineral stability

Gooding, J. L. (1978) Chemical weathering on Mars thermodynamic stabilities of primary minerals (and their alteration products) from mafic igneous rocks. 

The first point of discussion is the influence of the bedrock nature on the chemical composition of waters. We can see in Table II and in Fig. 6 that waters in the chloritic schist or argillaceous sand areas do not differ from those in the granitic area. This is not surprizing, in spite of the well-known control of rock mineral on the groundwater composition (M. Schoeller, 1962 Tardy, 1969) in fact, in the whole bioclimatic sequence considered, the lateritization processes have destructed all the primary minerals, except quartz, and the weathering minerals are always the same kaolinite, iron oxide and oxy-hydroxide, the stabilities of which in the surface are very great. 

The stability of minerals has long been of interest to soil scientists. One of the major processes occurring during the development of soils is the formation of secondary minerals from primary minerals. Plant nutrition in natural environments is dependent on mineral nutrients supplied by mineral weathering. Soil acidification, whether it results from natural processes of soil development or is accelerated by anthropic acidic deposition, is mediated by weathering processes. 

It is necessary to conclude that many of the mineral stability diagrams that are commonly constructed to explain primary mineral weathering (such as the one for feldspar in Figure 6.12) have no quantitative value—they are useful only to the extent that they gauge the tendency of the weathering reaction to proceed in a forward direction. If, for example, feldspar and kaolinite coexist in a soil, overall equilibrium between the two minerals is not possible when a realistic temperature and time frame is considered. The reaction is irreversible if it proceeds, feldspar must decompose and kaolinite must precipitate. It is true that back reactions such as the... 

Hydrotalcite. Synthetic hydrotalcite minerals are gaining commercial acceptance for thein abiHty to costabiHze PVC ia the presence of other primary stabilizers (see Table 2). The performance of the mixed metal stabilizers are particularly boosted when an equal part level, about 2—3 phr, of hydrotalcite is added to the PVC formulation. These minerals function by trapping HCl within the layered lattice arrangement of atoms. The formula. 

In the close-coupled scheme, all produts and minerals are sent to the catalytic process. Heavy deposits of carbonaceous substances are inevitable. Heavy products of preasphaltene should be converted as much as possible in the primary stage. The detailed characterization of all products, including orgnometallics, suggests ways to convert or stabilize the poison precursors in the primary stage. 

Some other practical situations where particle aggregation is important include the precipitation of colloidal mud at the mouth of a river due to the salinity of the sea-water exceeding the critical coagulation concentration, land (e.g. mountainside) stability, building and road foundations, the retention of a porous structure in filtration, mineral processing117 and paper making. Control of particle aggregation is also of primary importance in adhesives, inks, pharmaceuticals, cosmetics, foodstuffs and lubricants. 

Preparatively, it is important that mineral acids, carboxylic acids, and terf-carbenium ions can be added to alkenes via carbenium ion intermediates. Because of their relatively low stability, primary carbenium ions form more slowly in the course of such reactions than the more stable secondary carbenium ions, and these form more slowly than the even more stable tertiary carbenium ions (Hammond postulate ). Therefore, mineral and carboxylic acids add to unsymmetrical alkenes regioselectively to give Markovnikov products (see Section 3.3.3 for an explanation of this term). In addition, these electrophiles add most rapidly to those alkenes from which tertiary carbenium ion intermediates can be derived. 

The chemistry of these polysaccharides is dominated by partial esterification of the total number of carboxyl groups. The sequence of uronic acids in the primary structure is occasionally interrupted by rhamnose, and there is usually a trace of acetyl and phenolic substituents. Models developed from experimental data considered neutral side chains with DP = 2-10 (De Vries et al., 1982). These 1,4-a-linked linear uronans are susceptible to alkali—more so if the C-6 hydroxyl is esterified, but exceptionally acid-stable when this site is unsubstituted. Dispersion stability is less at higher DP. Uronans are endowed with strong dye-fixing and mineral-sequestering properties because of their charged surface. 

Admixes to the soil in stabilization process compound with the minerals and soil grains, and may lead to generation of new chemical mix with different properties in comparison with the primary properties of soil. Lime as an ordinary stabilizer compounds with soil in the form of quick-lime (CaO) or hydrated lime (Ca(OH)2) can improve soil physical properties [7]. 

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