Mechanical minerals

Modern coal-mining practice tends towards the use of mechanical devices, such as Cardox, Hydrox Mechanical Miners rather than explosives. This will not necessarily reduce the number of coal mine explosions because these may be, and indeed are known to be, initiated by other means such as faulty electrical equipment, breakage of electrical cables or other means of producing a hot spark or arc... 

Putnis A. (2002) Mineral replacement reactions from macroscopic observations to microscopic mechanisms. Mineral. Mag. 66(5), 689-708. 

Penn R L and Banfieid J F 1999 Formation of rutiie nuciei at anatase (112) twin interfaces and the phase transformation mechanism in nanocrystaiiine titania Am. Miner. 84 871... 

The mechanism of esterification of an alcohol in the presence of a mineral acid is now considered to involve the following steps. 

The observation already discussed ( 2.2, 2.3, 2.4) of nitrations, in concentrated and aqueous mineral acids and in pure nitric acid, which depend on the first power of the concentration of the aromatic compound, does not help much in elucidating the mechanisms of nitrations under these conditions. In contrast, the observation of zeroth-order... 

Physical Dilution. The flame retardant can also act as a thermal sink, increasing the heat capacity of the polymer or reducing the fuel content to a level below the lower limit of flammabiHty. Inert fillers such as glass fibers and microspheres and minerals such as talc act by this mechanism. 

Adsorption Mechanisms. The following mechanisms of adsorption are responsible for the formation of mineral—reagent bonds. 

Chemical Bond Formation (Chemisorption). This is the mechanism that leads to the formation of the strongest bonds between coUectors and mineral surfaces. Chemically adsorbed reagents usuaUy form surface compounds at the active waU sites. The flotation of calcite (CaCO ) and... 

Two main operational variables that differentiate the flotation of finely dispersed coUoids and precipitates in water treatment from the flotation of minerals is the need for quiescent pulp conditions (low turbulence) and the need for very fine bubble sizes in the former. This is accompHshed by the use of electroflotation and dissolved air flotation instead of mechanically generated bubbles which is common in mineral flotation practice. Electroflotation is a technique where fine gas bubbles (hydrogen and oxygen) are generated in the pulp by the appHcation of electricity to electrodes. These very fine bubbles are more suited to the flotation of very fine particles encountered in water treatment. Its industrial usage is not widespread. Dissolved air flotation is similar to vacuum flotation. Air-saturated slurries are subjected to vacuum for the generation of bubbles. The process finds limited appHcation in water treatment and in paper pulp effluent purification. The need to mn it batchwise renders it less versatile. 

Two air-saturation systems suited for use in water treatment are shown in Figure 15 (31). Such mechanisms faciHtate the release of air that generates much finer bubbles than mechanical air dispersion methods used in mineral flotation practice. 

Somatotropin, the P-adrenergic agonists, and the anaboHc steroids are considered metaboHsm modifiers because these compounds alter protein, Hpid, carbohydrate, mineral metaboHsm, or combinations of these and they partition nutrient use toward greater rates of protein deposition, ie, muscle growth, and lesser rates of Hpid accretion. Historical data leading to understanding of the mechanism (s) of action are found in reviews on anaboHc steroids (1), somatotropin (2—4), and the phenethano1 amines (5—7). 

Mg4Al2(OH) 2C02 3H20, is commonly written however, these minerals are generally non stoichiometric by nature and can include some amounts of alternative elements in then compositions. They function similarly to the zeoHtes but exist in layered stmctures and have a different trapping mechanism. In addition to then performance enhancement, the hydrotalcite minerals are compatible with PVC and can be used effectively in clear PVC appHcations as well as the pigmented formulations. 

Other Industrial Applications. High pressures are used industrially for many other specialized appHcations. Apart from mechanical uses in which hydrauhc pressure is used to supply power or to generate Hquid jets for mining minerals or cutting metal sheets and fabrics, most of these other operations are batch processes. Eor example, metallurgical appHcations include isostatic compaction, hot isostatic compaction (HIP), and the hydrostatic extmsion of metals. Other appHcations such as the hydrothermal synthesis of quartz (see Silica, synthetic quartz crystals), or the synthesis of industrial diamonds involve changing the phase of a substance under pressure. In the case of the synthesis of diamonds, conditions of 6 GPa (870,000 psi) and 1500°C are used (see Carbon, diamond, synthetic). 

As for other biological substances, states of dynamic equiUbrium exist for the various mineral nutrients as well as mechanisms whereby a system can adjust to varying amounts of these minerals in the diet. In forms usually found in foods, and under circumstances of normal human metaboHsm, most nutrient minerals are not toxic when ingested orally. Amounts considerably greater than the recommended dietary allowances (RDAs) can generally be eaten without concern for safety (Table 1) (3). 

The treatments used to recover nickel from its sulfide and lateritic ores differ considerably because of the differing physical characteristics of the two ore types. The sulfide ores, in which the nickel, iron, and copper occur in a physical mixture as distinct minerals, are amenable to initial concentration by mechanical methods, eg, flotation (qv) and magnetic separation (see SEPARATION,MAGNETIC). The lateritic ores are not susceptible to these physical processes of beneficiation, and chemical means must be used to extract the nickel. The nickel concentration processes that have been developed are not as effective for the lateritic ores as for the sulfide ores (see also Metallurgy, extractive Minerals recovery and processing). 

Many older finishes can be removed with single solvents or blends of petroleum solvents and oxygenates. Varnish can be removed with mineral spirits, shellac can be stripped with alcohols, and lacquers can be removed with blends of acetates and alcohols (lacquer thinners). The removal mechanism is one of dissolving the coating, then washing the surface or wiping away the finish. This method is often used to reamalgamate or liquefy old finishes on antique items of furniture. 

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