Tetrametaphosphoric acid

Sodium tetrametaphosphate [13396-41-3] M 429.9, pKj 2.60, pKj 6.4, pKj 8.22, pK 11.4 (tetrametaphosphoric acid, H4P4O12). Crystd twice from water at room temperature by adding EtOH (300g of Na4P40i2,H20, 2L of water, and IL of EtOH), washed first with 20% EtOH then with 50% EtOH and air dried [Quimby J Phys Chem 58 603 1954]. 

Tetrametaphosphoric acid behaves in aqueous solution as a strong acid 326, 334), the fourth H+ ion of which is, however, appreciably more weakly dissociated than the first three 62). Solutions of their alkali salts are neutral. 

HPOs, Monometaphosphoric acid. (HPOj)j, Dimetaphosphoric acid. (HPOj)j, Trimetaphosphoric acid. (HP03)4, Tetrametaphosphoric acid. (HPOa)4, Pentametaphosphoric acid. (HPOa) Hexametaphosphoric acid. 

An important class of condensed phosphoric acids is that in which each phosphate tetrahedron is bonded by oxygen atoms to two other tetrahedra. These acids have the composition (HPOgJ, with x - 3,4, 5,6, . They are called the metaphosphoric acids. Among these acids are tetrametaphosphoric acid and hexametaphosphoric acid. 

Other preparative methods Free tetrametaphosphoric acid. 

For total % P2O5 > 86.1, small amounts of trimeta- and tetrametaphosphoric acid were also detected. 1 = ortho-, 2 = pyro-, 3 = tri-, 4 = tetra-phosphate, etc. Highpoly = higher-molecular-weigfit material including 15-phosphoric acid. 

Under controlled conditions of hydrolysis, the cage-like molecules of P40]q will disintegrate by rupture of successive P-O-P linkages to form a variety of products. The main process entails the rupture of two P-O-P linkages to give cyclic tetrametaphosphoric acid as indicated in (4.49). 

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