Abstract: A method of leaching of the metal contents in natural silicates by means of mineral acids to produce a metal-containing leaching liquid and a solid residue is disclosed. The silicate is first crushed but the grain size of substantially all of it is kept above 0.1 mm. It is then leached for a period of time sufficient to form a solid residue consisting chiefly of silica. The process is controlled so that the grains do not change in size or shape in the course of the leaching process. The silicate to be leached may be anorthosite or olivinrich rock and the solid residue from the leaching process may be utilized for building material, as a source for silicon in industrial processes, as a catalyst or carrier of catalysts or as an absorbent.

Abstract: A mixer-settler apparatus is disclosed. The outlet tubes from the settler section are made positively adjustable in height so that proper phase separation can be obtained under varying conditions.

Abstract: Method of producing aluminiumchloride with a low content of magnesium from hydrochloric acid solutions which contain ions of aluminium and magnesium and from which the aluminiumchloride is precipitated by hydrochloric gas and where the precipitation is carried out continuously in cascade so that the major part of the aluminium will be precipitated from solutions in which the ratio between aluminium and magnesium calculated as g Al.sup.+3 /g Mg.sup.+2 is above 0,5. Produced aluminiumchloride may be transformed to aluminiumoxide by calcination.

Abstract: Method of producing aluminiumchloride with low contents of iron from solutions containing ions of aluminium and iron by precipitation of aluminiumchloride by means of hydrochloric gas where the solution from which the aluminiumchloride is precipitated contains at least 0.1 g Fe/l which solution has been formed by leaching of a natural mineral raw material or artifically produced aluminium-containing raw material by leaching with hydrochloric acid and/or sulphuric acid, respectively a mixture of such acids. The produced aluminiumchloride may be transformed to aluminiumoxide by calcination.

Abstract: Yttrium oxide with particularly big particles is formed by reacting yttrium ions with oxalate ions so that yttrium oxalate is precipitated. The precipitated yttrium oxalate is maintained at a temperature of 90.degree.-100.degree. C. for a period from 1/2 to 24 hours for formation of a crystal form of yttrium oxalate which can be dried and ignited to oxide without disintergrating. The heat-treatment can be combined with the precipitation and also with the subsequent drying and ignition to yttrium oxide.

Abstract: A process for the extraction of alumina from aluminum-containing silicates is disclosed. The process comprises acid leaching of the raw material, iron extraction, precipitation of the aluminum fraction as the aluminum chloride hexahydrate, removal of sodium chloride and calcination to alumina. The process can be made continuous with substantial regeneration and recycling of process components.