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Trimetaphosphates from polyphosphates

The complex preparative interrelationships occurring in the sodium polyphosphate system are summarized in Fig. 12.21 (p. 531). Thus anhydrous NaH2p04, when heated to 170" under conditions which allow the escap>e of water vapour, forms the diphosphate Na2H2p207, and further dehydration at 250" yields either Maddrell s salt (closed system) or the cyclic trimetaphosphate (water vapour pressure kept low). Maddrell s salt converts from the low-temperature to the high-lemperaturc form above 300", and above 400" reverts to the cyclic... [Pg.529]

A comparative study of the products of dehydration of the dihydrogen monophosphates of polyvalent cations showed that the stable end-products for cations with ionic radii between 0.57 and 1.03 A. (Cu++, Mg++, Ni++, Co++, Fe++, Mn++, Zn"1-1", Cd++, A1+++) are tetrametaphosphates. When the cations are either larger or smaller the end-products of dehydration are crystalline high-molecular polyphosphates (Li+, Be++, K+, Rb+, Cs+, Ag+, Zn++, Cd++, Hg++, Ca++, Sr++, Ba++ Pb++, Cr+++, Fe+++, Bi+++). In the case of the alkali salts only sodium trimetaphosphate occurs as a condensed phosphate with a cyclic anion (304, 305). Up to the present, an alkali tctrametaphosphate has not been observed as the dehydration product of a dihydrogen monophosphate. Consequently, alkali tetrametaphosphates arc obtainable only indirectly. Reference is made later (Section IV,C,4) to the fact that the tetraphosphates of barium, lead, and bismuth are formed as crystalline phases from melts of the corresponding composition. There are also reports of various forms of several condensed phosphates of tervalent iron and aluminum (31, 242, 369). [Pg.14]

Formation of trimetaphosphate anions from those of Graham s salt also occurs in solution. In water this process is not associated with hydrolytic cleavage of the P—0—P bonds, as was at first assumed (10, 322), but is independent of it (361). Thus polyphosphates of long-chain amines which are soluble in benzene form trimetaphosphate quantitatively on warming the anhydrous solution (359). This transformation follows Ostwald s rule for successive transformations, since trimetaphosphates are more stable than polyphosphates (322). [Pg.44]

Perhaps the formation of trimetaphosphate and small quantities of tetrametaphosphate from dissolved polyphosphates, which can amount to 70% in presence of Mg++ ions, is an indication of the form in which the anion chains are present in the solution. In any case this formation of trimetaphosphates is not, contrary to what was proposed initially (293, 326), an argument for the assumption that trimetaphosphate rings constitute a structural unit in the polyphosphates. Thus in solutions of Maddrell s salt, the anions of which are known to be linear chains from crystal structure determination (78) (see Section IV,E,2), up to 50% yields of trimeta-... [Pg.44]

The /3-form of the arsenatophosphate and /3-KAs03 contain trimeric anionic rings. This follows from the isomorphism with the low temperature form of K3(P309), which is formed when KH2P04 is treated with a mixture of acetic acid and acetic anhydride 121). It may also be concluded from the observation that in the hydrolysate of /3-arsenatophosphate it is possible to detect, in addition to monoarsenate and a little trimetaphosphate, only mono- and diphosphate, but no tri- or higher polyphosphate 121). The /3-forms of arsenatophosphates contain anions of the types ... [Pg.63]

Maddrell s salt, which are interpreted as showing that kinetic effects are responsible for difficulties in converting the cyclic trimer into the linear polymeric forms. The potassium polyphosphate samples (Kurrol s salt) obtained from the fusion of potassium sulphate and phosphoric acid have chains terminated by OSOJ groups, according to i.r. spectra. Kinetic studies show a first-order dependence of polyphosphate concentration in the hydrolysis of Graham s salt to give trimetaphosphate and short-chain species. The vaporization of sodium metaphosphate from a Knudsen cell leads to predominantly monomeric, with some dimeric, species, according to mass-spectrometric data. ... [Pg.322]

Anhydrous trimetaphosphates MCaPaOg, where M = Na, K, or NH4, can be obtained by heating the hydrates, which crystallize from aqueous solution to 180 °C. Further heating to 500 °C converts the sodium salt into a high molecular weight polyphosphate while the potassium compound gives a second trimetaphosphate modification. The ammonium salt loses ammonia and phosphorus pentoxide to give calcium polyphosphate. [Pg.525]


See other pages where Trimetaphosphates from polyphosphates is mentioned: [Pg.17]    [Pg.17]    [Pg.339]    [Pg.529]    [Pg.167]    [Pg.159]    [Pg.18]    [Pg.26]    [Pg.39]    [Pg.46]    [Pg.50]    [Pg.327]    [Pg.45]    [Pg.1148]    [Pg.95]    [Pg.198]    [Pg.529]    [Pg.204]    [Pg.43]    [Pg.54]    [Pg.66]    [Pg.82]    [Pg.124]    [Pg.148]    [Pg.218]    [Pg.289]   
See also in sourсe #XX -- [ Pg.4 , Pg.40 ]

See also in sourсe #XX -- [ Pg.40 ]




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Trimetaphosphate

Trimetaphosphates

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