Amorphous magnesium hydroxide

In neutral and alkaline environments, the magnesium hydroxide product can form a surface film which offers considerable protection to the pure metal or its common alloys. Electron diffraction studies of the film formed ia humid air iadicate that it is amorphous, with the oxidation rate reported to be less than 0.01 /rni/yr. If the humidity level is sufficiently high, so that condensation occurs on the surface of the sample, the amorphous film is found to contain at least some crystalline magnesium hydroxide (bmcite). The crystalline magnesium hydroxide is also protective ia deionized water at room temperature. The aeration of the water has Httie or no measurable effect on the corrosion resistance. However, as the water temperature is iacreased to 100°C, the protective capacity of the film begias to erode, particularly ia the presence of certain cathodic contaminants ia either the metal or the water (121,122). 

The data on thermal decomposition of activated magnesium hydroxide are well described by the first-order equation. The rate constant increases by a factor of 5-7 while the time of magnesium hydroxide activation in a vibration mill increases till 6 h. An increase of the decomposition rate is due to the fact that the nuclei formation of a new phase is simplified in the case of amorphous phase not only on the surface but also in the bulk. 

Aluminum silicate Aminotrimethylene phosphonic acid Barium hydroxide lime Calcium metasilicate Calcium sulfate Calcium sulfate dihydrate Cellulose Diatomaceous earth Diatomaceous earth, amorphous Magnesium carbonate Sodium polyacrylate Talc filler, paper coatings Aluminum silicate dihydrate Bentonite Calcium metasilicate Whiting Wollastonite filler, paper sizing Kaolin... 

Cotton (Gossypium herbaceum) Cottonseed meal Diatomaceous earth Diatomaceous earth, amorphous Dolomite Kaolin Magnesium carbonate Magnesium hydroxide Mica Nepheline syenite Pyrophyllite Silica, amorphous Silica, amorphous hydrated Silica, fumed Strontium sulfate... 

Elimination eliminating silica through lime softening with magnesium chloride or magnesium hydroxide is very effective a reducing the concentration of amorphous silica and silicates. 

The saturation levels for common cooling-water scales were calculated, including calcium carbonate, calcium sulfate, amorphous silica, and magnesium hydroxide. Brudte saturation levels were included because of the potential for magnesium silicate formation as a result of the adsorption of silica upon precipitating magnesium hydroxide. Three categories of systems were encountered [24] ... 

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... 

Transparent red iron oxides containing iron oxide hydrate can also be produced directly by precipitation. A hematite content of > 85 % can be obtained when iron(II) hydroxide or iron(II) carbonate is precipitated from iron(II) salt solutions at ca. 30 °C and when oxidation is carried out to completion with aeration and seeding additives (e.g., chlorides of magnesium, calcium, or aluminum) [5.271], Transparent iron oxides can also be synthesized by heating finely atomized liquid pentacarbonyl iron in the presence of excess air at 580-800 °C [5.272], [5.273]. The products have a primary particle size of ca. 10 nm, are X-ray amorphous, and have an isometric particle form. Hues ranging from red to orange can be obtained with this procedure, however, it is not suitable for yellow hues. 

In a closed system equipped with an oil bubbler, 30 ml of tetrahydrofuran were added to a mixture of 4-amino-5-chloro-2-methoxybenzoic acid, 2.02 g (0.010 mole) and l,l -carbonyldiimidazole, 1.62 g (0.010 mole) with stirring. When evolution of carbon dioxide ceased, nitrogen was bubbled through the reaction mixture for 1 hr. A solution of 3-aminoquinuclidine, 1.26 g (0.010 mole) in 10 ml tetrahydrofuran was added dropwise to the stirred reaction mixture and stirring at room temperature continued for 3 hrs. TLC analysis (3% cone, ammonium hydroxide solution in methanol) showed some product formation. The mixture was heated at reflux temperature for 18 hours and then concentraded to an oil. TLC analysis showed the presence of the product, imidazole and 3-aminoquinuclidine. The oil was dissolved in methylene chloride (75 ml) and washed twice with 50 ml portions of aqueous sodium bicarbonate solution. The methylene chloride layer was dried over anhydrous magnesium sulfate and concentrated to yield 2.0 g (67%) of a glassy amorphous solid, the free base of the title compound. 

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