Phosphorous availability

Parfitt RL, Yeates GW, Ross DJ, Mackay AD, Budding PJ (2005) Relationship between soil biota, nitrogen and phosphorous availability and pasture growth under organic and conventional management. Appl Soil Ecol 28 1-13... 

Oehl, F., Oberson, A., Tagmann, H.U., Besson, J.M., Dubois, D., Mader, P., Roth, H.R., Frossard, E. 2002. Phosphorous budget and phosphorous availability in soils under organic and conventional management. Nutrient Cycling in Agroecosystems 62 25-35. 

How can oxidation-reduction reactions of iron and manganese influence nutrient release in flooded soil and sediment Under what conditions is phosphorous available ... 

Figure 7.45 shows the XRD pattern of Li2BP05 phosphor. In the standard JCPDS data, there is no XRD pattern of Li2BP05 phosphor available for comparison. The XRD pattern did not indicate the presence of the constituents carbonates or traces of ammonia gas, which is indirect evidence of the formation of the desired compound. These results indicate that the final product was formed in homogeneous and crystalline form. 

It was found that that in the case of soft beta and X-ray radiation the IPs behave as an ideal gas counter with the 100% absorption efficiency if they are exposed in the middle of exposure range ( 10 to 10 photons/ pixel area) and that the relative uncertainty in measured intensity is determined primarily by the quantum fluctuations of the incident radiation (1). The thermal neutron absorption efficiency of the present available Gd doped IP-Neutron Detectors (IP-NDs) was found to be 53% and 69%, depending on the thicknes of the doped phosphor layer ( 85pm and 135 pm respectively). No substantial deviation in the IP response with the spatial variation over the surface of the IP was found, when irradiated by the homogeneous field of X-rays or neutrons and deviations were dominated by the incident radiation statistics (1). 

Triple (Concentrated) Superphosphate. The first important use of phosphoric acid in fertilizer processing was in the production of triple superphosphate (TSP), sometimes called concentrated superphosphate. Basically, the production process for this material is the same as that for normal superphosphate, except that the reactants are phosphate rock and phosphoric acid instead of phosphate rock and sulfuric acid. The phosphoric acid, like sulfuric acid, solubilizes the rock and, in addition, contributes its own content of soluble phosphoms. The result is triple superphosphate of 45—47% P2 s content as compared to 16—20% P2 5 normal superphosphate. Although triple superphosphate has been known almost as long as normal superphosphate, it did not reach commercial importance until the late 1940s, when commercial supply of acid became available. 

An alternative process (97) for direct esterification of cresols using phosphoric acid, a slow reaction, was developed in Israel, where phosphoms oxychloride is not locally available. 

The large amount of fluorine values released from phosphate rock in the manufacture of fertilisers (qv) gives a strong impetus to develop fluorine chemicals production from this source (see Phosphoric acid and the phosphates). Additional incentive comes from the need to control the emission of fluorine-containing gases. Most of the fluorine values are scmbbed out as fluorosiUcic acid, H2SiPg, which has limited useflilness. A procedure to convert fluorosihcic acid to calcium fluoride is available (61). 

Alternative Processes. Because of the large quantity of phosphate rock reserves available worldwide, recovery of the fluoride values from this raw material source has frequently been studied. Strategies involve recovering the fluoride from wet-process phosphoric acid plants as fluosiUcic acid [16961-83-4] H2SiFg, and then processing this acid to form hydrogen fluoride. 

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... 

Hydrogen use as a fuel in fuel cell appHcations is expected to increase. Fuel cells (qv) are devices which convert the chemical energy of a fuel and oxidant directiy into d-c electrical energy on a continuous basis, potentially approaching 100% efficiency. Large-scale (11 MW) phosphoric acid fuel cells have been commercially available since 1985 (276). Molten carbonate fuel cells (MCFCs) ate expected to be commercially available in the mid-1990s (277). 

About 264,000 metric tons of elemental capacity is available in North America, plus another 79,000 t (P equivalent) of purified wet phosphoric acid (14). About 85% of the elemental P is burned to P2 5 hydrated to phosphoric acid. Part of the acid (ca 21%) is used direcdy, but the biggest part is converted to phosphate compounds. Sodium phosphates account for 47% calcium, potassium, and ammonium phosphates account for 17%. Pinal apphcations include home laundry and automatic dishwasher detergents, industrial and institutional cleaners, food and beverages, metal cleaning and treatment, potable water and wastewater treatment, antifree2e, and electronics. The purified wet acid serves the same markets. 

The radioactive isotopes available for use as precursors for radioactive tracer manufacturing include barium [ C]-carbonate [1882-53-7], tritium gas, p2p] phosphoric acid or pP]-phosphoric acid [15364-02-0], p S]-sulfuric acid [13770-01 -9], and sodium [ I]-iodide [24359-64-6]. It is from these chemical forms that the corresponding radioactive tracer chemicals are synthesized. [ C]-Carbon dioxide, [ C]-benzene, and [ C]-methyl iodide require vacuum-line handling in weU-ventilated fume hoods. Tritium gas, pH]-methyl iodide, sodium borotritide, and [ I]-iodine, which are the most difficult forms of these isotopes to contain, must be handled in specialized closed systems. Sodium p S]-sulfate and sodium [ I]-iodide must be handled similarly in closed systems to avoid the Uberation of volatile p S]-sulfur oxides and [ I]-iodine. Adequate shielding must be provided when handling P P]-phosphoric acid to minimize exposure to external radiation. 

Phosphoric Acid. This acid is the primary acidulant in cola beverages. Phosphoric acid is stronger than most organic acids and weaker than other mineral acids. The dibasic properties of phosphoric acid provide minor buffering capacity in the beverage. Food-grade phosphoric acid is commercially available in concentrations of 75%, 80%, and 85% and is one of the most economical acidulants. 

Sodium Phosphate Manufacturing. Some pure carbon dioxide gas is available as a by-product ia plants manufacturiag sodium phosphate from sodium carbonate [497-19-8] and phosphoric acid [7664-38-2]. Two carbon dioxide plants were iastalled prior to 1962 to utilize this by-product gas. 

Nitrilotriacetonitrile [628-87-5], N(CH2CN)2, a precursor to nitrilotriacetic acid [139-13-9], N(CH2COOH)2, can be prepared from the reaction of formaldehyde cyanohydrin with ammonia (26). Formaldehyde cyanohydrin is also used as an intermediate in pharmaceutical production. Commercial formaldehyde cyanohydrin is available as a 70% aqueous solution stabiLhed by phosphoric acid. 

Activated alumina and phosphoric acid on a suitable support have become the choices for an iadustrial process. Ziac oxide with alumina has also been claimed to be a good catalyst. The actual mechanism of dehydration is not known. In iadustrial production, the ethylene yield is 94 to 99% of the theoretical value depending on the processiag scheme. Traces of aldehyde, acids, higher hydrocarbons, and carbon oxides, as well as water, have to be removed. Fixed-bed processes developed at the beginning of this century have been commercialized in many countries, and small-scale industries are still in operation in Brazil and India. New fluid-bed processes have been developed to reduce the plant investment and operating costs (102,103). Commercially available processes include the Lummus processes (fixed and fluidized-bed processes), Halcon/Scientific Design process, NIKK/JGC process, and the Petrobras process. In all these processes, typical ethylene yield is between 94 and 99%. 

Fire Hazards - Flash Point Not flammable Flammable Limits in Air (%) Not flammable Fire Extinguishing AgerUs Not pertinent Fire Extinguishing Agents Not To Be Used Not pertinent Special Hazards of Combustion Products Oxides of sulfur and phosphorous may be formed when exposed to a fire situation Behavior in Fire Data not available Ignition Temperature Not pertinent Electrical Hazard Not pertinent Bunting Rate Not pertinent. 

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