Metaphosphate tetrametaphosphates

A further condensation occurs in the metaphosphates, 4P03, with a pseudo cation anion ratio 1 1. In these compounds, phosphor has still the same coordination number, but the POf " ions are either condensed to rings, e.g. in the tetrametaphosphate (NH4)4(P4012), or to chains of infinite length, the structure of the phosphates in a tetrametaphosphate being... 

P03] J -groups, the metaphosphates, in which, however, not only ring-shaped complex anions, such as are found in (NH4)4(P03)4 ammonium tetrametaphosphate (Romers), but also very long chains occur as in glassy meta-phosphoric acid itself. 

Modem cyclic formulation of tetrametaphosphate anion suggested by A. Glatzel. (Ring structure of metaphosphate definitely established by L. Pauling and J. Sherman 1937.)... 

On heating, some tetrametaphosphates revert to tri metaphosphates while others form long-chain polyphosphates (5.173). 

Neodynium ultraphosphate, NdPjO (5.185), is an efficient and much-used laser material. The cyclic tetrametaphosphates MNdP40j2 (M = Li, Na, K), the ortho phosphates M3Nd(P04)2, M = Na, K, fluorapatite doped with Nd + or Ho + and Nd-doped metaphosphate glasses are also efficient laser materials. 

Lead(II) metaphosphates formulated as dimetaphosphate Pb(P03)2, trimetaphosphate J[Pb3(P03)6.3H2O], tetrametaphosphate Pb2(P03)4 and hexametaphosphate Pb3(P03>6 have been claimed. Preparations usually involve the action of alkali metaphosphate upon soluble lead(II) salts, but conditions appear to be critical for obtaining the right pro-ducti47. 148.149. Fusion methods involving lead nitrate and phosphorus(V) oxide have also been usediso. 

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