Über die Bildungsweise von Polyanionen in wäßriger Lösung : Der Additionsmechanismus bei der Tetrawolframatbildung

Abstract

A reaction mechanism is developed for the first steps of the formation of isopolytungstates in acidified aqueous tungstate solutions. Because of the fast rate of formation for the tetratungstate ion an addition mechanism is assumed where a WO6 octahedron is built up by addition of a reactive WO4 tetrahedron to another tetrahedron or to an octahedron already formed. Considering different criterions the large number of isopolytungstates which is principly possible can be restricted to just one, namely a tetratungstate ion constructed from 4 WO42- and 4 H+ ions, which is in agreement with experiments. The discussion leads to the structural characteristics for stable polytungstates and to a model for the structure of the tetratungstate ion.