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The presented paper is oriented to the processing of the results obtained from the measurement of the physical and chemical properties of the synthetic melts of the system FeO-SiO 2 -Fe 2 O 3 . On the basis of these results and knowledge obtained from the literature, we present an image of these melt structures. The structure of the system FeO-SiO 2 -Fe 2 O 3 may be characterized as an amorphous solidified melt. The basic structural component of such sets is the chemical compound fayalite (2FeO • SiO 2 ), which is ionized in cation Fe 2+ and anion complex SiO 4 4-. In the course of melting, the components are ionized, and formed are simple cations (e.g., Fe 2+ , FeO + , and Fe 3+ ), anion complexes (e.g., SiO 4 4-, FeO 2 -, Fe 2 O 5 4-, SiFeO 7 7-, FeO 3 3-, etc.) and, clusters, the composition of which corresponds to the present chemical components (for example: wu ¨stite, magnetite, fayalite). Tetrahedral SiO 4 4is a principal structural unit of the silicate melts. When increasing its content in the system, polymerization occurs with the formation of more complex anions (e.g., Si 2 O 7 6-, Si 3 O 10 8-, Si 3 O 9 6-, Si 2 O 6 4-, etc.). Knowledge about the non-negligible effect of iron upon the properties of these melts was obtained from analysis of the physical and chemical properties of the fayalite melt. Ferrous oxide behaves in these systems as the donor of the oxygen anions. The gradual transfer of the ferrite-oxygen complexes from tetrahedral to octahedral co-ordination depends on the reduction in the number of oxygen anions in the system. Existence of the individual ferrito-oxygen and silico-oxygen complexes is reflected in the physical properties of the fayalite melts.

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