Abstract: A process for treating fluoride-contaminated scrap lining material from electrolytic reduction cells comprises mixing the material with 7-30 parts of sulphuric acid and sufficient water to bring liquid content to 60-80 parts per 100 parts of lining material, mixing in sufficient lime to at least neutralize the sulphuric acid and make the slurry slightly alkaline, the slurry then being allowed to set into a solid mass.The slurry should be of a paste-like consistency. The lime may be wholly calcium hydroxide, but a substantial proportion may be in the form of calcium carbonate.The scrap, before or after the above treatment with lime and sulphuric acid, is preferably heated to 150.degree.-500.degree. C. in the presence of water vapor to destroy cyanides.

Abstract: A starting solid mixture of AlCl.sub.3 and Nacl, which may have been obtained by acid leaching of an aluminiferous mineral and precipitation of the AlCl.sub.3 and NaCl, is mixed with water in an amount to form an aqueous solution containing NaCl and AlCl.sub.3 in a weight ratio Na.sub.2 O/Al.sub.2 O.sub.3 of about 0.028. This is sparged with HCl to precipitate AlCl.sub.3, but the sparging is stopped before a substantial concentration of NaCl starts to come out of solution. The precipitated AlCl.sub.3 may be calcined to Al.sub.2 O.sub.3 and washed to remove any residual NaCl.

Abstract: A process for the production of alumina from siliceous minerals containing substantial quantities of combined aluminium and calcium comprises the steps of treating the finely divided mineral with a hot acid liquor containing chloride, fluoride and calcium ions to extract alumina values from the mineral; recovering aluminium chloride from the liquid extract; recycling one fraction of the spent extract to the mineral extraction stage; and treating another fraction of the spent extract to regenerate hydrogen chloride gas for re-use in the process.