Zinc residue

The processing of bauxite aluminium ore (hydrated alumina oxides) exemplifies these processes. In the Bayer process hot concentrated sodium hydroxide dissolves alumina which is subsequently separated and crystallized as aluminium hydroxide (hydrometallurgy). This is calcined to anhydrous alumina (pyrometallurgy) before being reduced in the Hall process (electrometallurgy) wherein alumina serves as the electrode from which elemental aluminium is deposited on the cathode. 

Metal scrap also includes enormous quantities of post-use items such as industrial machinery, vehicles, metal furniture, washing machines, and other consumer equipment, as well as metal residues from electroplating baths, wastewater treatment sludges, and the like. 

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Amalgamated zinc residues isolated from Clemmensen reduction of an alkyl aryl ketone in glacial acetic acid were pyrophoric, and had to be immediately dumped into water after filtration to prevent ignition. 

Zinc residues from reduction of nitrobenzene to N-phenylhydroxylam inc are often pyrophoric and must be kept wet dining disposal. 

Zinc residues from poorly mixed priming paint spontaneously inflamed after prolonged exposure to atmosphere. Aluminium residues may behave similarly. 

Adult 25 Maximum kidney zinc residue after 18 days was 14.1 g/kg DW vs. 4.9 g/kg in controls 18... 

Newt, Triturus cristatus, adults, held in tank with a zinc-plated base South African clawed frog, Xenopus laevis 200 to 3000 overa 7-day period Zinc-poisoned newts were lethargic, ate poorly, and had skin darkening prior to death. Zinc residues were elevated in kidney, brain, liver, and intestine, when compared to controls. The hippocampus region of the brain of poisoned newts contained zinc-rich cells 82... 

To a mixture of 50 g (0.4 mol) of nitrobenzene, 180 ml of 30% sodium hydroxide, 20 ml of water and 50 ml of ethanol, 100-125g (1.5-1.9g-atom) of zinc dust is added portionwise with efficient mechanical stirring until the red liquid turns light yellow. After stirring for an additional 15 minutes, 1 liter of cold water is added, the mixture is filtered with suction, the solids on the filter are washed with water, and the hydrazobenzene is extracted from the solids by boiling with 750 ml of ethanol. The mixture is filtered while hot, the filtrate is cooled, the precipitated crystalline hydrazobenzene is filtered with suction, and the mother liquor is used for repeated extraction of the zinc residue. Recrystallization of the crude product from an alcohol-ether mixture gives hydrazobenzene of m.p. 126-127°. 

To a solution of the p-bromophenacyl ester of 6-ethyl-5-methyl-3,6-dihydro-2H-pyran-2-carboxylic acids (46.0 g, 0.125 mol) in glacial AcOH (650 ml) was slowly added zinc (dust, 49.31 g, 0.754 mol) in a 60 min-period at room temperature. The reaction mixture was stirred at room temperature for 8 h, then filtered on Celite, and the zinc residue washed with AcOH (200 ml), then THF (200 ml). Most of the solvent was evaporated and the crude reaction mixture diluted with Et20 and washed with H20 (2x150 ml). The organic layer was treated with a diluted NaOH solution to pH 10. The aqueous phase was washed with Et20 several times, then acidified with a 1.0 N HCI solution to pH 4, and extracted with Et20. The combined organic extracts were... 

Step 7. Centrifuge and pour the supernate into a clean centrifuge tube. Discard solid zinc residue. 

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