Abstract: Gaseous perfluorocarbons in a waste gas are adsorbed by an adsorption device. Subsequently a decomposition of the perfluorocarbons takes place with formation of hydrogen fluoride. The hydrogen fluoride is converted with an oxide of a metal to be reduced, to the metal fluoride thereof. The metal fluoride formed is then fed again to the reduction process.

Abstract: A sensor is provided for measuring the concentration of a fluorocarbon in the offgas during molten salt electrolysis of metal compounds. The measurement takes place at time intervals of less than 10 seconds and a controller initiates reduction in an electrolysis voltage if a fluorocarbon limit value of 25 ppm is exceeded.

Abstract: A method for synthesising a rare earth element by a redox reaction. The starting material side of the reaction for synthesising the rare earth element includes a rare earth compound, in which the rare earth element is present in a positive oxidation state, and hydrogen. The redox reaction takes place in two stages. First, a hydration reaction takes place between an elementary rare earth element and hydrogen to form a rare earth hydride. Then, a reaction takes place between the rare earth compound and the rare earth hydride. An elementary rare earth element and a hydrogen-containing compound are produced at the same time as the product of the reaction.

Abstract: Between an anode and a cathode, a salt melt containing a metal ion is separated from the anode by a gap across which an electric arc can be formed. The metal ion is deposited on the anode and subsequently removed.