The Structural Chemistry of Condensed Inorganic Phosphates

Abstract

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; anions. This has been shown in the case of pofyarsenatophosphates, 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 eflects. 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.

Thermodynamic aspects of the adsorption of hexametaphosphate on kaolinite

“…Since the hydrolysis processes of HMP are slow [11,12] and the measurements are performed in a time range of a few hours, the presence of hydrolysis products of HMP can be neglected and HMP can be considered as the only species in solution that can be adsorbed.…”

“…At neutral pH values, however, HMP reveals a remarkable stability toward the ring cleavage process, so that its hydrolysis proceeds quite slowly [11,12].…”

“…Literature concerning the behavior of sodium hexametaphosphate in water [10][11][12] supports a background knowledge for this study, because it makes it possible to characterize the chemistry of the deflocculant in solution. As in the case of all cyclic metaphosphates, the HMP ring undergoes cleavage by hydrolysis to form, in the first instance, the corresponding linear hexaphosphate through a reaction of the first order with respect to HMP [11,12].…”

“…As in the case of all cyclic metaphosphates, the HMP ring undergoes cleavage by hydrolysis to form, in the first instance, the corresponding linear hexaphosphate through a reaction of the first order with respect to HMP [11,12]. This linear hexaphosphate is then degraded into lower phosphates following at least three routes [11][12][13].…”

Pyrophosphate-bridged complexes with picomolar toxicity

“…More probable is the notion that these compounds dissociate and the mono-nuclear products formed gain cellular entry, possibly now by diffusion [40]. As mentioned earlier, pyrophosphate is sensitive to hydrolysis forming phosphate ðPO 3À 4 Þ anions [41][42][43]. To investigate this hypothesis, a stability study was conducted using 3.…”