Abstract: A method of treating an aqueous cyanide- and/or complexing-agent-containing solution, including high-temperature treating the solution in a closed reaction vessel, discharging at least a portion of the treated solution from the reaction vessel, at least partially replacing the discharged fraction with untreated solution, and subjecting the untreated solution to high-temperature treatment along with a treated-solution fraction remaining in the reaction vessel.

Abstract: In a method for working up a gold bath or a gold alloy bath, which contains gold in the form of a gold sulphite complex, working up takes place through at least one oxidant, which oxidizes the sulphite contained in the complex and reduces the gold contained in the complex to its metallic form. In the method in particular hydrogen peroxide and potassium-peroxo-monosulphate are used as oxidants. The oxidants are provided in a kit.

Abstract: In a method for working up a gold bath or a gold alloy bath, which contains gold in the form of a gold sulphite complex, working up takes place through at least one oxidant, which oxidizes the sulphite contained in the complex and reduces the gold contained in the complex to its metallic form. In the method in particular hydrogen peroxide and potassium-peroxo-monosulphate are used as oxidants. The oxidants are provided in a kit.

Abstract: In a method for the treatment of sewage containing nitrites comprising the reduction of the nitrite with urea in an acid medium it is provided, to obtain end products friendly to the environment and an economic conduction of the method, that a greatly acid urea solution be supplied and circulated through a pipe reactor, and that the sewage containing nitrite to be treated should be injected into the pipe reactor. Furthermore, the invention relates to a device for carrying out the method and to an examination device which is particularly suitable for the periodic determination of the nitrite content in a circulation duct.