Condensed inorganic phosphates
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
After it had become known that three types of condensed inorganic phosphates, i.e. metaphosphates, polyphosphates, and ultraphosphates, exist, attempts were made to elucidate their formation, properties, and mutual relationships. Metaphosphates and polyphosphates containing up to eight or ten monomer units can be separated chromatographically. In the melts, equilibria exist between the various types of phosphate anions. Annealing of the glasses leads to crystalline products, sometimes containing only one type of anion. The glass-crystal transition proceeds via monomeric XO-3 anions. This has been shown in the case of polyarsenatophosphates, in which the As atoms are randomly distributed over the chains in the vitreous state, but are located at preferred positions in the crystalline state. The maximum degree of dissociation of polyphosphates and polyphosphoric acids in water is 30%, which accounts for the ion exchange and the chelating effects. The cation-catalysed decomposition of polyphosphates can take place either by hydrolytic degradation from the chain ends, or by rearrangement within the chains to form metaphosphates.
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