Abstract: Mercury is removed from sulfuric acid-bearing hot and moist smelting-plant or roasting-plant gases by cooling and scrubbing the hot gases by means of a concentrated sulfuric acid mist in order to sulfatize the mercury and to separate it from the gases. The cooling is carried out by vaporizing so much water or dilute sulfuric acid solution from the gases that the temperature of the gas drops to below the dew point, in order to produce a sulfuric acid mist which sulfatizes and washes the mercury, the gases being separated from the mist and directed to the sulfuric acid plant. The process can be carried out by means of nozzles installed in the pipe which feeds hot and moist sulfuric acid-bearing gases into the scrubbing tower of the sulfuric acid plant, water or acid obtained from the scrubbing tower being fed through the nozzles into the feed pipe in the form of a finely-divided mist.

Abstract: A hydrometallurgical process for the treatment of a soluble silicate-bearing material for the recovery of its valuable metal content by leaching the silicate-bearing material at an elevated temperature with an aqueous solution of a mineral acid, precipitating silicic acid during the same stage in an easily settling and filtering form, the silicate-bearing material being added at such a rate that its concentration calculated as SiO.sub.2 corresponds to the simultaneously precipitating silicic acid quantity, and by finally separating the solid material from the valuable-metal-bearing solution.