Phosphate species

Relationship Between End Point Volumes for Solutions of Phosphate Species with HCl and NaOH... 

Hexafluorophosphoric Acid. Hexafluorophosphoric acid (3) is present under ambient conditions only as an aqueous solution because the anhydrous acid dissociates rapidly to HF and PF at 25°C (56). The commercially available HPF is approximately 60% HPF based on PF analysis with HF, HPO2F2, HPO F, and H PO ia equiUbrium equivalent to about 11% additional HPF. The acid is a colorless Hquid which fumes considerably owiag to formation of an HF aerosol. Frequently, the commercially available acid has a dark honey color which is thought to be reduced phosphate species. This color can be removed by oxidation with a small amount of nitric acid. When the hexafluorophosphoric acid is diluted, it slowly hydrolyzes to the other fluorophosphoric acids and finally phosphoric acid. In concentrated solutions, the hexafluorophosphoric acid estabUshes equiUbrium with its hydrolysis products ia relatively low concentration. Hexafluorophosphoric acid hexahydrate [40209-76-5] 6 P 31.5°C, also forms (66). This... 

Analysis. Excellent reviews of phosphate analysis are available (28). SoHds characterization methods such as x-ray powder diffraction (xrd) and thermal gravimetric analysis (tga) are used for the identification of individual crystalline phosphates, either alone or in mixtures. These techniques, along with elemental analysis and phosphate species deterrnination, are used to identify unknown phosphates and their mixtures. Particle size analysis, surface area, microscopy, and other standard soHds characterizations are useful in relating soHds properties to performance. SoHd-state nmr is used with increasing frequency. 

Compute the concentrations of the phosphate species in a H3P04 solution that has pH = 2.25, if the total concentration of all four forms of the dissolved phosphates is 15 mmol-L-1. 

Table 6.5. Crystalline phosphate species found in magnesium phosphate cements...

According to El-Mashri et al.,190 the A106 A104 ratio determines the hydration capacity of anodic oxides. Tetrahedral sites are hydrated easily to form a boehmite-like structure, which is known to be composed of double layers of Al-centered octahedra, weakly linked by water molecules to other layers.184 As the oxide formed in H3P04 contains about 70% tetrahedral aluminum bonds, its hydration ability should be higher than that of the oxide formed in tartrate solution. However, this has not been found in practice, which is interpreted by El-Mashri et al. as being due to some reduction of A104 by incorporated phosphate species. 

The equilibria among the species are dependent on the pH of the solution in much the same way as the equilibria among the various phosphate species (see Chapter 14). Not only is the formation of polyvanadates reminiscent of phosphorus chemistry, so is the fact that vanadium forms oxyhalides such as OVX3 and V02X. 

Phosphate reacts and forms insoluble compounds with many metals, particularly iron, aluminum, and calcium. Under acid soil conditions, both iron and aluminum become more soluble, and thus as soil pH decreases, its phosphate fixing power increases. This means that iron and aluminum react with phosphate to form insoluble species that are not available to plants. Under basic conditions, high concentrations of calcium exist and insoluble calcium phosphates form. Insoluble phosphate species are also formed with other metals that happen to be present however, the three mentioned are generally present in the highest concentration, and so they represent the major reactants with phosphate. Iron, aluminum, and calcium phosphates can also occur as coatings on soil particles. 

Column operation for adsorption and elution of phosphate species... 

Since properties of both arsenate and phosphate species are very close, the adsorption of phosphate species was studied prior to that of arsenate. The phosphate adsorption was tested by the following two methods (i) and (ii). Hereafter, flow rate and volume of feed are given in space velocity (SV, h 1)... 

Figure 15. Cyclic voltammogratn on Pt(ll I) at 10 mV for various pH solutions of 0.8 - 4.6, when the respective anion concentration was kept at 0. M. (A) Sulfate solutions at [sulfate species] = O.IM. (B) Perchlorate solutions at [CIO4] = 0.1 A/. (C) Phosphate solutions at 0. M ionic strength of phosphate species. (From Ref. 62.)...

H. A.-Kozlowska, J. Klinger, and B. E. Conway, /. Electroanal. Chem. 75, 45 (1911). Fukuda and A. Aramata, The kinetic study of adsorption processes of the phosphate species on platinum)111) in aqueous acidic solutions, J. Electroanal. Chem., in press (1997). 

Ion pairing of phosphate species. Source-. From Atlas, E., et al. (1976). Marine Chemistry, 4, 243-254. 

Note that equation 5.2 is irreversible and the product AMP will require two phosphorylation steps to reconstitute the high-energy adenosine triphosphate, ATP. Inositol 1,4,5-triphosphate is an important molecule in the cytosol, where it releases calcium ions from storage. It forms part of a series of inositol-phosphate species that mediate calcium ion concentrations inside and outside the cell. 

ToF-SIMS, and AFM results, the formation of ordered monolayers of octade-cylphosphoric acid on a Ta205 surface involves both monodentate and bi-dentate phosphate species [135]. In the case of goethite, (y-AlOOH), it was found that methylphosphonic acid bound to the surface as a monodentate or a bidentate species depending on the pH and the concentration [163]. 

Natural fibrous materials are identified somewhat by chance. For example, there are seven vanadate and seven vanadium oxysalt minerals on the list of fibrous minerals. These species are composed of a rare element, vanadium, but the fibrous samples may have attracted attention because they are often brightly colored. Vanadinite [Pb5(V04)3Cl] for example, is bright orange-red. Further, the list of natural mineral fibers we have compiled contains seventy-seven phosphate species. So many phosphates are listed because detailed descriptions of these mostly quite rare minerals were readily available (Nriagu and Moore, 1984). 

The specific adsorption of H2P04 ions that accompany the UPD of Zn + ions on Pt (platinized electrodes obtained by Pt electrodeposition on the gold-plated plastic foil) electrodes was studied by using a radiotracer method with P phosphate species in the presence of a great excess of C104 ions [196]. It was found that the specific adsorption of species induced... 

Mass balance Equate 2(calcium species) = 3(phosphate species). 

Herve et al. (57) investigated the thermal changes of structures by means of XRD and TG-DTA for Keggin-type heteropolyacids and proposed Scheme 2. Infrared spectroscopy of H4PMo, VO40 showed the release of vanadium atoms to form H3PM012O40 and vanadium phosphate species (55). Exposure to water vapor induces the decomposition of the latter (indicated by the disappearance of a band at ca. 1037-1030 cm -1) (58). 

Of the four prominent pure end-member phosphate species of the apatite group only dahllite (space group C63/m) is a common biomineral28. This carbonate apatite is a distinct variety of apatite rather than a mixture of CaC03 and hydroxyapatite. Expressed as oxides, the mineral content of bovine cortical bone (dry fat-free material) has the following chemical composition112 ... 

Fig. 15. Distribution of phosphate species at 20 °C (after Kester and Pytkowicz130))...

RuHAP was synthesized from a stoichiometric HAP, Ca10(PO4)6(OH)2, with RuCl3nH20. Analysis by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray (EDX), IR and Ru K-edge X-ray absorption fine structure (XAFS) showed that a monomeric Ru phosphate species is created on the HAP surface. Figure 5.2a shows a proposed surface structure of RuHAP. 

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