Abstract: The invention relates to a method for controlling a process operating by means of the electrochemical potential, in which process complex ores and/or concentrates are treated in order to arrange the valuable components in the materials in a form appropriate for further processing and in which method electrodes made of material essentially similar to the materials to be treated in the process. According to the invention an impedance analysis in connection with the measurement of the electrochemical potential is carried out for the material to be treated in process in order to analyze the state of the solid surface and/or the state between the solid material and the intermediary material. The measured values are utilized in the adjustment of the process parameters. In order to carry out the impedance analysis voltage pulses are conducted into the material in at least one frequency and in at least one value of the electrochemical potential of the material.

Abstract: The invention relates to a method for removing sulphur and nitrogen compounds from gases by means of long-chained sulphur compounds mainly in acidic conditions, with an electroconductive solid material serving as the carrier of the long-chained sulphur compounds. The properties of the solid material surface are adjusted to be favourable to the sulphur polymer by means of potential measurements with mineral electrodes.

Abstract: The invention relates to a method for measuring and adjusting electrochemical potential and/or component content in the process of treating valuable materials, when the valuable materials should be recovered either together or separately by aid of the values of the recovery range defined on the basis of electrochemical potential and component control. According to the invention, the measuring of electrochemical potential and/or component content is carried out by means of at least one electrode (4, 5), advantageously by means of a mineral electrode, so that in order to regulate the physicochemical state of the electrode and/or to remove the coating layer formed on the electrode surface and in order to protect the electrode, onto the electrode there is switched a supply voltage differing from the electrochemical balance potential of the electrode, which supply voltage is switched off before starting the measuring operation.

Abstract: A process for the exploitation of low-grade oxidic and iron-bearing complex ores or concentrates, whereby the initial materials are reduced in a rotary kiln at a temperature of 1000.degree.-1500.degree. C. in such a manner that the products are a magnetic fraction primarily consisting of iron, and a non-magnetic oxide fraction, the materials present in this fraction being further exploitable by conventional methods.

Abstract: The invention relates to a process for the froth flotation of complex ores. In accordance with this invention, froth flotation is carried out by using a collector and froth flotation conditions for which it has been calculated in advance that the said mineral and the collector form stable surface compounds. The conditions include the electrochemical potential of the system, the concentration of the collector, the pH, and other physical factors. According to this invention it has been observed that by adjusting the potential and the concentration of the collector separately for each mineral, each mineral can be frothed out separately from the slurry, the process being in this case specific for the mineral. When so desired, the different minerals of the ore slurry can also be frothed simultaneously by selecting the conditions where the Pourfaix-type diagrams of all minerals in said complex ore overlap under the conditions in question.

Abstract: The invention relates to a process for the recovery of valuable metals from sulfidic, silicate-containing raw materials by slurrying the raw material in water, by subjecting the slurry to a selective leach under atmospheric conditions and in an acidic milieu, and by separating the valuable-metal containing solution from the solid leach residue.When the leach is carried out by introducing an oxygen-bearing gas into the slurry which contains finely-divided sulfide and carbon, the acidity of the slurry drops in a controlled manner so that a high efficiency of oxygen, and a high selectivity of the leach as regards valuable metals, are obtained. Owing to the presence of carbon the oxygen is reduced very easily and so oxygen efficiency is high and the rate of dissolving of the valuable metals increases in the slurry mixture.

Abstract: An iron-free chromium(III) compound is precipitated at an elevated temperature and pressure from an acidic aqueous solution which contains iron and chromium. In order to prevent coprecipitation of iron, an additive is added to the precipitation stage in an amount sufficient to provide in the precipitation conditions at least 2 g/l of bivalent chromium in the solution.

Abstract: A process for coating an electrically nonconductive material with a metal by attaching a less noble metal or a compound thereof, in pulverous form, to the surface of the electrically nonconductive material and spraying a solution of the nobler metal on the surface thus coated in order to cause the nobler metal to adhere to the surface.

Abstract: A process for electrolytic recovery of zinc from zinc sulfate solutions according to the electrowinning principle, using an aluminum cathode and a zinc sulfate solution which is devoid of any organic substance and to which at least one of cobalt and nickel has been added in such an amount that the solution contains nickel less than 2 mg/l and cobalt less than 5 mg/l.

Abstract: A hydrometallurgical process for the treatment of a raw material which contains iron and other metals, with a sulfuric acid solution, in order to dissolve the metals and to precipitate and separate the iron, the separated metal sulfate solution being exposed to evaporation in order to crystallize and separate the metal sulfates from the mother liquor, which is recycled to the treatment stage performed with sulfuric acid solution, and the separated metal sulfate being recovered.