Solubilization phosphate

Saunders and Williams [79] have discussed ignition methods for the determination of organic phosphorus in soils. Sodium carbonate fusion has also been used to solubilize phosphate in soil analyses. 

The synthesis of the amprenavir derivative, which is equipped with a solubilizing phosphate group, takes a slightly different course from that used for the prototype. The protected intermediate 5 used in the synthesis of 12 is allowed to react with benzyloxycarbonyl chloride to provide the... 

For example, some plants can increase root volume and surface area to optimize uptake potential. Alternatively, plant roots and/or associated fungi can produce chelating compounds that solubilize ferric iron and calcium-bound phosphorus, enzymes and/or acids that solubilize phosphate in the root vicinity. Plants also minimize phosphorus loss by resorbing much of their phosphorus prior to litterfall, and by efficient recycling from fallen litter. In extremely unfertile soils (e.g., in tropical rain forests) phosphorus recycling is so efficient that topsoil contains virtually no phosphorus it is all tied up in biomass. 

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. 

Nitric Phosphate. About 15% of worldwide phosphate fertilizer production is by processes that are based on solubilization of phosphate rock with nitric acid iastead of sulfuric or phosphoric acids (64). These processes, known collectively as nitric phosphate or nitrophosphate processes are important, mainly because of the iadependence from sulfur as a raw material and because of the freedom from the environmental problem of gypsum disposal that accompanies phosphoric acid-based processes. These two characteristics are expected to promote eventual iacrease ia the use of nitric phosphate processes, as sulfur resources diminish and/or environmental restrictions are tightened. 

Carboxylate, sulfonate, sulfate, and phosphate ate the polar, solubilizing groups found in most anionic surfactants. In dilute solutions of soft water, these groups ate combined with a 12—15 carbon chain hydrophobe for best surfactant properties. In neutral or acidic media, or in the presence of heavy-metal salts, eg, Ca, the carboxylate group loses most of its solubilizing power. 

Scale and deposits are controlled through the use of phosphates, chelants, and polymers. Phosphates are precipitating treatments, and chelants are solubilizing treatments. Polymers are most widely used to disperse particulates but they are also used to solubilize contaminants under certain conditions. 

Developing agents must also be soluble in the aqueous alkaline processing solutions. Typically such solutions are maintained at about pH 10 by the presence of a carbonate buffer. Other buffers used include borate and, less frequendy, phosphate. Developer solubiUty can be enhanced by the presence of hydroxyl or sulfonamide groups, usually in the A/-alkyl substituent. The solubilization also serves to reduce developer allergenicity by reducing partitioning into the lipophilic phase of the skin (46). 

Chelant programs are solubilizing programs and are commonly prescribed for both FT and WT boilers either as replacements for, or used in combination with, phosphate precipitation programs. 

NOTE If the BW contains phosphate, the preferred reaction is for calcium to precipitate as hydroxyapatite, rather than to chelate with EDTA or NTA (a further competing anion effect). Consequently, there would seem to be no valid reason to produce combined phosphate-chelant programs, with the chelant acting as a reserve against unforeseen hardness incursions caused by a softener leakage, or other source. In practice, the chelant acts to solubilize existing deposits, producing a very clean boiler. 

Emulsions containing a water-solubile herbicide salt and a herbicide soluble in an organic solvent are prepared by a mixture of water, dioctyl phthalate, and isophorone. In this case ethoxylated poly ary lphenol phosphate neutralized with triethanolamine and ethoxylated acid phosphoric acid esters is used as emulsifier [231],... 

Solubilizing activity are also used in enhanced oil recovery. Tar and extremely viscous hydrocarbons are recovered by the injection of an aqueous solution of an anionic orthophosphate ester surfactant into a petroleum formation, retaining the surfactant in the formation for about 24 h, and displacing the solubilized hydrocarbons toward a recovery well. The surfactant forms an oil microemulsion with the hydrocarbons in the formation. An anionic monoorthophosphate ester surfactant which is a free acid of an organic phosphate ester was dissolved in water. The input of surfactant solution was 2-25% of the pore volume of the formation [250]. To produce a concentrate for the manufacture... 

The cobalt, nickel, and copper bis(2-ethylhexyl) phosphate surfactants dissolved in n-heptane lead to quasi-one-dimensional association microstructures, i.e., rodlike reversed micelles that increase in size via water solubilization [111],... 

The T2 site also became protected from tryptic hydrolysis after phosphorylation of the native or solubilized sarcoplasmic reticulum vesicles with inorganic phosphate in a calcium free medium in the presence of dimethylsulfoxide or glycerol [121,252]. Under these conditions the Ca -ATPase is converted into a covalent E2-P intermediate, that is analogous in conformation to the E2V intermediate formed in the presence of vanadate. In contrast to this, the T2 site in the stable phosphorylated Ca2E P intermediate generated by the reaction of the Ca -ATPase with chro-mium-ATP in the presence of Ca [178,253] was fully exposed to trypsin, just as it was in the nonphosphorylated Ca2Ei form. Therefore the phosphorylated intermediates show the same sensitivity to trypsin at the T2 site as the corresponding nonphosphorylated enzyme forms. 

Chemical modification studies with fluorescein-5 -isothiocyanate support the proximity of Lys515 to the ATP binding site [98,113-117,212,339]. Fluorescein-5 -isothiocyanate stoichiometrically reacts with the Ca -ATPase in intact or solubilized sarcoplasmic reticulum at a mildly alkaline pH, causing inhibition of ATPase activity, ATP-dependent Ca transport, and the phosphorylation of the Ca " -ATPase by ATP the Ca uptake energized by acetylphosphate, carbamylphos-phate or j -nitrophenyl phosphate is only partially inhibited [113,114,212,339]. The reaction of -ATPase with FITC is competitively inhibited by ATP, AMPPNP, TNP-ATP, and less effectively by ADP or ITP the concentrations of the various nucleotides required for protection are consistent with their affinities for the ATP binding site of the Ca -ATPase [114,212,340]. 

Especially in dicotyledonous plant species such as tomato, chickpea, and white lupin (82,111), with a high cation/anion uptake ratio, PEPC-mediated biosynthesis of carboxylates may also be linked to excessive net uptake of cations due to inhibition of uptake and assimilation of nitrate under P-deficient conditions (Fig. 5) (17,111,115). Excess uptake of cations is balanced by enhanced net re-lea,se of protons (82,111,116), provided by increased bio.synthesis of organic acids via PEPC as a constituent of the intracellular pH-stat mechanism (117). In these plants, P deficiency-mediated proton extrusion leads to rhizosphere acidification, which can contribute to the. solubilization of acid soluble Ca phosphates in calcareous soils (Fig. 5) (34,118,119). In some species (e.g., chickpea, white lupin, oil-seed rape, buckwheat), the enhanced net release of protons is associated with increased exudation of carboxylates, whereas in tomato, carboxylate exudation was negligible despite intense proton extrusion (82,120). 

The growth of ectomycorrhizal trees is frequently improved by their increased phosphorus (P) accumulation (3), and this, in turn, is related to the intensity of the mycorrhizal infection. Ectomycorrhizal fungi solubilize insoluble forms of A1 and Ca phosphates as well as inositol hexaphosphates, though a wide interstrain variability has been recorded (112). These complex P forms are digested by the secretion of extracellular acid and alkaline phosphomono- and phosphodi-ester-ases. Pi in soil solutions is easily taken up by ectomycorrhizal hyphae and then translocated to the host roots. Its absorption and efflux are probably regulated... 

F. Lapeyrie, J. Ranger, and D. Vairelles, Phosphate-solubilizing activity of ectoniy-corrhizal fungi in vitro. Can. J. Bol. 69 342 (1991). 

G. J. D. Kirk and M. A. Saleque, Root-induced solubilization of phosphate in the rhizosphcre of lowland rice. New Phytol. 729 325 (1995). 

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