Minerals surface area

Minerals require a suitable mucosal surface across which to enter the body. Resection or diversion of a large portion of small bowel obviously affects mineral absorption. Extensive mucosal damage due to mesenteric infarction or inflamatory bowel disease or major diversion by jejunoileal bypass procedures reduces the available surface area. Minerals whose absorption occurs primarily in the proximal intestine, e.g., copper or iron, are affected differently than those absorbed more distally, e.g., zinc. In addition, the integrity of the epithelium, the uptake of fluids and electrolytes, the intracellular protein synthesis, the energy-dependent pumps, and the hormone receptors must be intact. 

In general, high-surface-area minerals such as layer silicate clays and allophane dissolve at significant rates in strongly acid soils ... 

Posttreatment fines migration is quite common in sandstone acidizing. It may be difficult to avoid in many cases. The reaction of HE with clays and other aluminosilicate minerals and quartz can release undissolved fines. Also, new fines may be generated as a result of partial reaction with high-surface-area minerals, particularly clays and certain zeolites, in which they more rarely occur. 

Zeolite A high surface area mineral that is used in sorption pumps and cryosorption traps. The zeolite structure is characterized by internal cavities that are accessible through windows, the openings of which can be selected between 3 and 7 A, which allows the selective adsorption of gases or vapors depending on their molecular diameter. Zeolites must be regenerated at 200°C or more. Zeolites are also called Molecular sieves. 

Filtration. In many mineral processing operations, filtration follows thickening and it is used primarily to produce a soHd product that is very low in moisture. Filtration equipment can be either continuous or batch type and either constant pressure (vacuum) or constant rate. In the constant pressure type, filtration rate decreases gradually as the cake builds up, whereas in the constant rate type the pressure is increased gradually to maintain a certain filtration rate as the cake resistance builds. The size of the device is specified by the required filter surface area. 

Tricalcium phosphate, Ca2(P0 2> is formed under high temperatures and is unstable toward reaction with moisture below 100°C. The high temperature mineral whidockite [64418-26-4] although often described as P-tricalcium phosphate, is not pure. Whidockite contains small amounts of iron and magnesium. Commercial tricalcium phosphate prepared by the reaction of phosphoric acid and a hydrated lime slurry consists of amorphous or poody crystalline basic calcium phosphates close to the hydroxyapatite composition and has a Ca/P ratio of approximately 3 2. Because this mole ratio can vary widely (1.3—2.0), free lime, calcium hydroxide, and dicalcium phosphate may be present in variable proportion. The highly insoluble basic calcium phosphates precipitate as fine particles, mosdy less than a few micrometers in diameter. The surface area of precipitated hydroxyapatite is approximately... 

Sheet form, 914 mm (36 in.) in width, or widths agreed upon by purchaser and suppHer, composed of asphalt-saturated organic felt with approximately half the width of weather side coated with asphalt and surfaced with mineral granules, for use as cap sheet in constmction of BUR. Materials covered by this specification, in minimum mass per unit area, are Type I, 1806 g/m (37.0 lb/100 fU) Type II, 2260 g/m (46.3 lb/100 fU) Type III, 1733 g/m (35.5 lb/100 fU) and Type IV, 2090 g/m (42.8 lb/100 fU). 

Example 4 Calculation of Sample Weight for Surface Moisture Content An example is given with reference to material with minimal internal or pore-retained moisture such as mineral concentrates wherein physically adhering moisture is the sole consideration. With this simphfication, a moisture coefficient K is employed as miiltipher of nominal top-size particle size d taken to the third power to account for surface area. Adapting fundamental sampling theory to moisture sampling, variance is of a minimum sample quantity is expressed as... 

The oil and gas lease under homestead law would simply be the right to conduct drilling operations on a person s surface property. The lease would not constitute a claim to minerals found under a particular surface area as under the rule of capture rule. Since the resci voir could be reached from different surface locations with slant drilling, the economic rent of a homestead lease would be far less than the value of a capture-rule lease. The difference in value would accrue to the driller-finder, thereby encouraging production by making drilling more efficient and profitable. 

Secondary minerals. As weathering of primary minerals proceeds, ions are released into solution, and new minerals are formed. These new minerals, called secondary minerals, include layer silicate clay minerals, carbonates, phosphates, sulfates and sulfides, different hydroxides and oxyhydroxides of Al, Fe, Mn, Ti, and Si, and non-crystalline minerals such as allophane and imogolite. Secondary minerals, such as the clay minerals, may have a specific surface area in the range of 20-800 m /g and up to 1000 m /g in the case of imogolite (Wada, 1985). Surface area is very important because most chemical reactions in soil are surface reactions occurring at the interface of solids and the soil solution. Layer-silicate clays, oxides, and carbonates are the most widespread secondary minerals. 

The properties described above have important consequences for the way in which these skeletal tissues are subsequently preserved, and hence their usefulness or otherwise as recorders of dietary signals. Several points from the discussion above are relevant here. It is useful to ask what are the most important mechanisms or routes for change in buried bones and teeth One could divide these processes into those with simple addition of new non-apatitic material (various minerals such as pyrites, silicates and simple carbonates) in pores and spaces (Hassan and Ortner 1977), and those related to change within the apatite crystals, usually in the form of recrystallization and crystal growth. The first kind of process has severe implications for alteration of bone and dentine, partly because they are porous materials with high surface area initially and because the approximately 20-30% by volume occupied by collagen is subsequently lost by hydrolysis and/or consumption by bacteria and the void filled by new minerals. Enamel is much denser and contains no pores or Haversian canals and there is very, little organic material to lose and replace with extraneous material. Cracks are the only interstices available for deposition of material. 

The examples discussed above suggest useful directions for future research involving trace element analysis of bones. Specifically, the effects of developmental age and other factors (e.g., porosity, mineralization) that may lead to differences in surface area of specimens should be considered. Diage-netic effects should be monitored by analysis of a suite of elements whose abundances are not controlled by dietary abundances (e.g., Mn, Zr, etc.). Finally, although alkaline elements such as Sr and Ba are most likely to reflect the Sr/Ca and Ba/Ca levels of the diet, omnivores such as humans are likely to obtain the majority of these elements from plants rather than from animals. Therefore for accmate diet reconstruction it is necessary to determine the total abundance of Ca as and the Sr/Ca and Ba/Ca ratios of the plant and animal resources that were potential dietary staples. The effects of culinary practices on elemental abundances (Burton and Wright 1995 Katzenberg et al. this volume) must also be evaluated. 

The above-mentioned consideration indicates that important factors controlling the precipitations of barite and silica are surface area/water mass ratio (A/M), temperature, precipitation rate constant (k) and flow rate (u), and the coupled fluid flow-precipitation models are applicable to understanding the distributions of minerals in submarine hydrothermal ore deposits. 

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