Alkali polyphosphate

Partial replacement of cations when using excess of alkali phosphate was at first interpreted by supposing that the cations were in part bound as a complex with the polyphosphates. This led to incorrect conclusions regarding the molecular size of polyphosphates, which persist even now in the designation of Graham s salt as hexametaphosphate. The correct interpretation of these very complicated relationships stems from the discovery that in dilute solutions of polyphosphates even salts of the alkali metal ions are only partially dissociated—up to a maximum of 30-40% 260, 280, 282, 288, 333). The degree of dissociation a for alkali polyphosphates depends on many factors. Thus, for example, the effective degree of... 

A range of high-molecular alkali polyphosphates occur in several crystalline forms. In the case of the sodium and potassium compounds the trivial names Maddrell s and Kurrol s salts have been adopted and these... 

Chitosan and some of its derivatives, which are cationic polyelectrolytes, when mixed with alkali polyphosphates (anionic polyelectrolytes) will produce insoluble or gel-like macromolecular complexes. These are reported to be of use in microcapsules and in biotechnology. The structures of these materials are not known, but they presumably involve cross-linking between the chitosan and polyphosphate chains (10.32). 

Several different components may be present in a particular detergent formulation. In varying proportions, these include alkalies, polyphosphates, various surfactants, and chelating agents, as well as acids. 

Complex Ion Formation. Phosphates form water-soluble complex ions with metallic cations, a phenomenon commonly called sequestration. In contrast to many complexing agents, polyphosphates are nonspecific and form soluble, charged complexes with virtually all metallic cations. Alkali metals are weakly complexed, but alkaline-earth and transition metals form more strongly associated complexes (eg, eq. 16). Quaternary ammonium ions are complexed Htde if at all because of their low charge density. The amount of metal ion that can be sequestered by polyphosphates generally increases... 

Oxygen chelates such as those of edta and polyphosphates are of importance in analytical chemistry and in removing Ca ions from hard water. There is no unique. sequence of stabilities since these depend sensitively on a variety of factors where geometrical considerations are not important the smaller ions tend to form the stronger complexes but in polydentate macrocycles steric factors can be crucial. Thus dicyclohexyl-18-crown-6 (p. 96) forms much stronger complexes with Sr and Ba than with Ca (or the alkali metals) as shown in Fig. 5.6. Structural data are also available and an example of a solvated 8-coordinate Ca complex [(benzo-l5-crown-5)-Ca(NCS)2-MeOH] is shown in Fig. 5.7. The coordination polyhedron is not regular Ca lies above the mean plane of the 5 ether oxygens... 

Phosphates are another common ingredient of alkali cleaners. They have both detergent and peptisation properties. The pyro- and polyphosphates in particular have water softening capabilities. 

Sodium fluoride also attacks silica, as do sodium metaphosphate and sodium polyphosphate, and to a lesser extent sodium carbonate and sodium cyanide. Attack is particularly vigorous for fused alkalis, alkali halides and phosphates. 

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). 

Ions which do not have a rare gas configuration appear not to fit into this rule. They are much more firmly bound than the alkali and alkaline earth cations. A dependence on radius is not observed and for Hg(I) the binding is stronger with the diphosphate anion than with triphosphate 366). (See, also the binding of cations by highmolccular polyphosphates, Section IV,E,/,d.) For the analysis and determination of triphosphates, see Section VII,B. 

Micellar systems (i.e.,. Shenoy 1984 Ohlendorf Brunn) as well as other colloidal systems (polyphosphates (Hunston), tri-n-butyl-tin-fluoride, e.g. Dunn Evans) come under the heading surfactants . It is necessary to differentiate soaps into anionic, cationic, and non-ionic types. Among the anionic types one can find, for instance, alkali metals and ammonium salts consisting of various fatty acids, which were... 

Oxygen, carbon dioxide and various chemicals used to reduce scaling can cause corrosion. Corrosion control is provided largely by the use of inhibitors such as chromates, polyphosphates, silicates and alkalies. 

The effect of cations on the rate of hydrolysis of cycio-tri- and cvc/o-tetra-phosphates has also been studied.260 Alkali metal cations retarded the hydrolysis of both cyclo-phosphates in acidic solution but accelerated the reaction in basic solution. The catalytic activity followed the sequence Li+ > Na+> K+. Mg11, Ca11 and Ni11 retarded the hydrolysis of the cyclo-phosphates in the pH range 1.0-2.0 or 1.0-2.7, but accelerated the reaction at pH>3. Catalysis by Cu11 is observed above pH 2, while Alni has a marked catalytic effect at pH 1 and 2. A variety of other papers have appeared dealing with metal ion-promoted hydrolysis of polyphosphates.261-264 However, the mechanistic details of these reactions remain unclear and the catalytically active complexes remain undefined. 

It should be pointed out that neither of the methods described above was aimed at obtaining completely unmodified preparations of cellular condensed polyphosphates. Other, much milder, methods of extraction from cells have been developed in order to obtain samples of condensed phosphates, which are as little modified as possible to completely avoid the use of strong acids and alkali. 

Figure 8.14 Changes in the content of nucleic acids, phospholipids, Pi and PolyPs, and the activities of exopolyphosphatase (PolyPase) and pyrophosphatase (PPase) during synchronous growth of Schizosaccharomyces pombe (Kulaev et al., 1973b) (a) 1, number of cells PL, phospholipids OP, P J P, total phosphate (b) PPi, acid-soluble polyphosphate PP2, salt-soluble polyphosphate (c) PP3, alkali-soluble polyphosphate PP4, hot-perchloric-acid-soluble polyphosphate JZPolyP, total polyphosphate.

Some representative linear polyphosphates are the alkali salts M PjO, (pyrophosphates) and M5P3Oi0 (tripolyphosphates). Many detergents contain Na5P3Oi0, and it has other industrial uses. In detergents the triphosphate serves to sequester Ca2+ and Mg2+ ions. Using Ln3+ ions as models, the mode of complexation was shown by nmr to involve attachment of two tetradentate P3Ofo ions. 

Phosphorus has an even wider range of oxoacid chemistry, and a commensurately wide range of phosphates, phosphites, polyphosphates, hypophosphites, and so on of the alkali metals are preparable. Sodium and potassium are the most common cations used, largely because of their availability and low cost. The cation often has little effect on the properties and applications, which are covered in Phosphates Solid-state Chemistry. Most form a variety of crystalline hydrates, which have been well covered in previous treatments and need not be repeated here. Trae to form, lithium is the exception, forming no stable hydrates with phosphorus oxoanions. 

Harold reported that incubation of the mycelium of Neurospora crassa with inorganic phosphate resulted in formation of a complex, possibly consisting of polyphosphate bound to the free amino groups of a 2-amino-2-deoxygalactan. Mahadevan and Tatum found that precipitation of the alkali-soluble portion of N. crassa cell-walls with ammonium sulfate provided a fraction containing a 2-amino-2-deoxygalactose, glucuronic acid residues, and protein. 

Properties. The polyphosphates of the alkali or alkaline earth metals are soluble in water, the trifunctional branch points being un-... 

Uranium(VI) polyphosphates, (U02)2(P30io)2 H20, were obtained by precipitation of a uranyl solution with Na5P30io M2UO2P2O7, with M = alkali metal, have been synthesized by heating... 

Alkali metal and alkaline earth polyphosphates crystallize as short chains, two to six phosphate groups per chain or very long chains with hundreds to thousands of PO3 per chain. All polyphosphates in the alkali metal and alkaline earth systems are amorphous in the intermediate chain lengths. Control of the short chain length polyphosphates, both crystalline or amorphous, is a function of R, the M2O-P2O5 ratio. The control of the chain lengths of very long crystalline polyphosphates as Maddrell s salt, Kurrol s salt, and calcium phosphate fibers is not well understood. 

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