Metaphosphates hydrates

An abrasive is usually chemically inert, neither interacting with other dentifrice ingredients nor dissolving in the paste or the mouth. Substances used as dentifrice abrasives include amorphous hydrated silica, dicalcium phosphate dihydrate [7789-77-7] anhydrous dicalcium phosphate [7757-93-9] insoluble sodium metaphosphate [10361-03-2], calcium pyrophosphate [35405-51-7], a-alumina trihydrate, and calcium carbonate [471-34-1]. These materials are usually synthesized to specifications for purity, particle size, and other characteristics naturally occurring minerals are used infrequently. Sodium bicarbonate [144-55-8] and sodium chloride [7647-14-5] have also been employed as dentifrice abrasives. 

The crystal structure of the cyc/<7-hcxaphos-phate anion in Nar.P OiR.fiHoO shows that all 6P atoms are coplanar and that bond lengths arc similar to those in the P Oy and p40i2 anions. See ref. 147 for the structure of the hydrated cyc/o-decaphosphate KioPit)03o.4H20. Higher cyr/r)-metaphosphates can be isolated by... 

J. P. Guthrie, Hydration and Dehydration of Phosphoric Acid Derivatives Free Energies of Formation of the Pentacoordinate Intermediates for Phosphate Ester Hydrolysis and of Monomeric Metaphosphate, J. Am. Chem. Soc. 1977, 99, 3391. 

Hexachloroethane, removal from zirconium (IV) chloride, 4 124 Hexachloroplumbic(IV) acid, 1 48 Hexaguanidonium tetraphosphate 1-hydrate, 5 97, 100 Hexahalogenoplumbic acids, 1 48 Hexahalogenotellurates(IV), 2 188 Hexaiodostannates(IV), formation of, by tin(IV) iodide, 4 121 Hexametaphosphates (see Metaphosphates)... 

As the tetroxide has been shown to have the formula of a mixed anhydride, it should yield phosphorous and phosphoric acids on treatment with watbr. Actually, the solution, after neutralisation with sodium hydroxide, showed the reactions of phosphites and metaphosphates. The hydration may therefore be represented by an equation... 

Metaphosphates become hydrated in neutral and alkaline as well as in acid solution, according to the equations... 

Uranyl pyrophosphate, (U03)2P207, is formed as a precipitate when a solution of sodium metaphosphate is poured into a hot solution of uranyl nitrate. The tetrahydrate, (U02)2P20,.4H20, is precipitated in yellow microcrystals by double decomposition of sodium pyrophosjihate and uranyl nitrate. The hydrate loses water and yields the anhydrous salt at 120° C. Uranyl pyrojohosphate is insoluble in water, alcohol, or ether but it dissolves in excess of sodium pyrophosphate solution (see below), and also in dilute nitric acid. 

In acid environments proteins may form protein-phosphate complexes of low solubility. The metaphosphates, which are less hydrated than the ortophosphates, form complexes that are less soluble than those with ortophosphates. This has been utilized for the modification of functional properties of protein concentrates and preparations, for separation of proteins in different food processing operations, and in treatment of protein-containing food plant effluents. 

NMR exchange experiments for the study of surface dissolution species in solution-aged metaphosphate glass has been reported. It has been demonstrated that use of CP allows the resonances of phosphate tetrahedral species within the hydrated dissolution surface to be selectively and cleanly edited from the bulk unaged phosphate species. Incorporating the CP-editing into a 2D RFDR exchange experiment also has allowed the local spatial connectivity between these surface dissolution phosphate species to be directly addressed. 

P40i2Na4-4H20 Sodium tetra-metaphosphate 4-hydrate, 6 98 P40i2Na, Sodium tetraphosphate, 6 99... 

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