Magnesium slurries

A magnesium slurry in ether can be used to prepare benzol-cyclobutenylmethylmagnesiumbromide at — 50° without the rcarrangcmcnttoo-vinyl-phenylmethylmagnesium bromide, usually encountered with other preparations of the metal.7... 

Methoxy-2-methyl-4-phenyl-l-beDzoteIluriiiiiini Trifluoromethanesulfonatc2 1 ml] of a solution of 1.57 g (10 mmol) of bromobenzene in 5 ml] of dry tetrahydrofuran is added to a slurry of 0.41 g (17 mmol) of magnesium turnings in 3 ml] of dry tetrahydrofuran. A 20 mg crystal of iodine is added and, when the iodine color has faded, the rest of the bromobenzene solution is added dropwise to the magnesium slurry. The mixture is heated under reflux for 1 h, a solution of l.Og (3.3 mmol) of 7-methoxy-2-methyl-4-oxo-477-l-benzotellurin in 5 ml] of dry tetrahydrofuran is added, the resultant mixture is heated under reflux for 1 h, and then cooled to 0°. A saturated aqueous solution of ammonium chloride is added dropwise, the resultant mixture is diluted with 100 ml] of water, and then extracted with three 25 ml] portions of dichloromcthane. 

A few years later an apparatus was described [25] in which a highly reactive magnesium slurry was prepared by evaporation of magnesium at 5 x 10 bar from an alumina crucible in a simple rotating-solution reactor (Fig. 5.1). 

Carbonate is measured by evolution of carbon dioxide on treating the sample with sulfuric acid. The gas train should iaclude a silver acetate absorber to remove hydrogen sulfide, a magnesium perchlorate drying unit, and a CO2-absorption bulb. Sulfide is determined by distilling hydrogen sulfide from an acidified slurry of the sample iato an ammoniacal cadmium chloride solution, and titrating the precipitated cadmium sulfide iodimetrically. 

Martin Marietta Magnesia Specialties, Inc. (Pittsburgh, Peimsylvania, formerly Clearwater, Inc.) hydrates MgO to produce magnesium hydroxide slurry containing 58% soflds (73). 

Production and Shipment. Magnesium hydroxide is produced and shipped in aqueous slurry or as dry powder. 

Bulk density is 1.49 kg/L for 57% solids slurry with a Mg(OH)2 loading of 0.85 kg/L. The properties of some magnesium hydroxide slurries are given in Table 12. 

Instmmentation and control guidelines for processes utilizing magnesium hydroxide and other slurries have been outlined (82). An experimental deterrnination of the accuracy of magnetic dow meters for magnesium hydroxide slurries d owing in pipelines (qv) has been reported (83). 

Slurry Viscosity. Viscosities of magnesium hydroxide slurries are determined by the Brookfield Viscometer in which viscosity is measured using various combinations of spindles and spindle speeds, or other common methods of viscometry. Viscosity decreases with increasing rate of shear. Fluids, such as magnesium hydroxide slurry, that exhibit this type of rheological behavior are termed pseudoplastic. The viscosities obtained can be correlated with product or process parameters. Details of viscosity deterrnination for slurries are well covered in the Hterature (85,86). 

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... 

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