Aqueous complexes with phosphate ions

Experimental stoichiometty of the complexes in [1990ELY/BRI] Equilibrium constant, logio Proposed stoichiomehy of die complexes in [1990ELY/BRI] 

Quantitative solubihty experiments have been described in [1956CHU/STE], [1967MOS/ESS], [1994BAG/FOU], [19950ST], [1999FOU/LAG] and 

Chukhlantsev and Stepanov found logio = -57.6 for h-doped Th3(P04)4(s) and suggest that the difference between this value and the other two determinations is due to the formation of Th3(0H)3(P04)3(s) but no evidence for this is presented. For reasons given in Appendix A these values have not been accepted by the present review. It can be noted that these values differ significantly from that proposed in [1994BAG/FOU], logi = -(112 + 2.1). 

The equilibrium constant reported by [1956CHU/STE] for the reaction Th(HP04)2(s, hyd) Th + 2HPOf 

Moskvin et al. [1967MOS/ESS] have reported equilibrium constants, log,, for the reactions  

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Protactinium can be recovered from solutions 2-8M in nitric or hydrochloric acids by extraction with tributyl phosphate, isobutyl methyl ketone or other organic solvents. The protactinium can be stripped from the solvent by aqueous acid fluoride solutions the addition to these solutions of Al3 + ion or boric acid, which form stronger complexes with fluoride ion than... 

Ligand (264) has been prepared and complexed with Ru" to give [Ru(264)(4-Metpy)] + which protonates on the cyclam N atoms to give a series of species up to [Ru(H3264)(4-Metpy)] +. In aqueous solution, the system acts as a selective luminescent sensor for ATP (with respect to phosphate, sulfate, and chloride ions). Oxaaza macrocycles attached to the 4 -position of tpy either directly or with a spacer as in (265) have been synthesized in addition, l,10-diaza-18-... 

The fact that twelve molybdate ions are bound to each phosphate unit in molybdophosphate has been exploited as an amplifying factor. The molybdophosphoric acid is extracted from the original solution into a mixture of diethyl ether or chloroform with butanol, in order to eliminate the excess of molybdate reagent it is then re-extracted into an aqueous phase and broken down with alkali. The molybdate ions are reacted with ammonium rhodanide90 or aminochlorobenzenethiol76 to give coloured products with absorption maxima at 470 and 710 nm, respectively. One phosphate ion thus yields twelve molybdate units, the optical absorbance is amplified with respect to that of the heteropoly phosphate complex and its measurement provides a sensitive determination procedure. 

This chargeless molecule can be extracted by ether or amyl alcohol. In addition to this a set of complex ions, such as [Fe(SCN)]2+, [Fe(SCN)2]+, [Fe(SCN)4]-, [Fe(SCN)5]2-, and [Fe(SCN)6]3 are also formed. The composition of the product in aqueous solution depends mainly on the relative amounts of iron and thiocyanate present. Phosphates, arsenates, borates, iodates, sulphates, acetates, oxalates, tartrates, citrates, and the corresponding free acid interfere due to the formation of stable complexes with iron(III) ions. 

Specific interactions between starch and proteins were observed as early as the beginning of the twentieth century. Berczeller996 noted that the surface tension of aqueous soap solutions did not decrease with the addition of protein (egg albumin) alone, but it did decrease when starch and protein were added. This effect was observed to increase with time. Sorption of albumin on starch is inhibited by bi- and trivalent ions and at the isoelectric point. Below the isoelectric point, bonding between starch and albumin is ionic in character, whereas nonionic interactions are expected above the isoelectric point.997 The Terayama hypothesis998 predicts the formation of protein complexes with starch, provided that starch exhibits the properties of a polyelectrolyte. Apart from chemically modified anionic starches (such as starch sulfate, starch phosphate, and various cross-linked starch derivatives bearing ionized functions), potato starch is the only variety that behaves as a polyelectrolyte. Its random phosphate ester moieties permit proteins to form complexes with it. Takeuchi et a/.999-1002 demonstrated such a possibility with various proteins and a 4% gel of potato starch. 

Most solution reactions that lead to the formation of aqueous inorganic complexes are endothermic, thus the complexes increase in stability with increasing temperature (see Fig. 1.6). This applies to the formation of most metal complexes with sulfate, fluoride, bicarbonate, carbonate, and phosphate ions (cf. Christensen et al. 1975 Smith and Martell 1976 Nordstrom et al. 1990). In other words the hotter the water is, the more the metal species in it will be present as complexes with these ligands rather than as free ions. Complexation thus tends to increase the mobilities of most metals at elevated temperatures. For example, the reaction... 

The mixture to be separated contains [U02] and Pu(TV) nitrates, as well as metal ions such as 3gSr. Kerosene is added to the aqueous solution of metal salts, giving a two-phase system (i.e. these solvents are immiscible). Tributyl phosphate (TBP, a phosphate ester) is added to form complexes with the uranium-containing and plutonium ions, extracting them into the kerosene layer. The fission products remain in the aqueous solution, and separation of the solvent layers thus achieves separation of the fission products from Pu- and U-containing species. Repeated extractions from the aqueous layer by the same process increases the efficiency of the separation. 

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