STUDY OF ACID-BASE PROPERTIES OF TUNGSTEN-MOLYBDATE MELTS OF DIFFERENT CATION COMPOSITION UNDER EQUILIBRIUM CONDITIONS
Abstract
Due to their important properties, molybdenum and tungsten oxides and bronzes of different stoichiometric composition are widely used in various fields of science and technology. Melts based on tungstates and molybdates of alkaline and alkaline earth metals have practical applications for obtaining these materials. According to modern views, molybdenum and tungsten bronzes of alkaline and alkaline earth metals are solid solutions of the entry of these metals into tungsten (molybdenum) (VI) oxide. Obtaining these bronzes is carried out by chemical and electrochemical methods of synthesis. Electrochemical cells with oxygen indicator electrodes and reference electrodes are used to study changes in the activity of oxygen ions in the tungstate melt. The experimental change in the potentials of the oxygen electrode in case of addition of oxygen ion acceptors in the form of molybdates and tungstates of alkali or alkaline earth metals is explained by the proposed model of the ionic composition of the melt taking into account the formation of cationized complexes involving alkali and alkaline earth metals. Mathematical calculations of potential values of oxygen electrodes make it possible to predict the composition (number of cations) of cationized complexes. Cations Sr2+, Ba2+, Li+, Mg2+, Zn2+ interact with molybdate and tungstate anions to form the corresponding cationized complexes. The ability to form complexes increases with an increase in the specific charge of the cation. The production of molybdenum and tungsten bronzes of different compositions is determined by the possibility of changing the electroreduction potential of molybdenum and tungsten compounds, and in the case of high-temperature electrochemical synthesis, by the possibility of their displacement and combination with the potential of the second component of the synthesis.
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