Orthophosphates condensations

Waters and wastewaters may contain orthophosphates, condensed phosphates (poly- and metaphosphates) and organic phosphorus compounds. Under natural conditions free from human influence, concentrations of phosphorus... 

If not easily hydrolysed to soluble orthophosphates, condensed phosphates are usually best identified and estimated by the techniques of paper chromatography or x-ray diffraction (XRD) (see below). Several purely chemical methods are, however, known. 

Condensed phosphates are derived by dehydration of acid orthophosphates. The resulting polymeric stmctures are based on a backbone of P—O—P linkages where PO tetrahedra are joined by shared oxygen atoms. The range of materials within this classification is extremely broad, extending from the simple diphosphate, also known as pyrophosphate, to indefinitely long-chain polyphosphates and ultraphosphates (see Table 1). Both weU-defined crystalline and amorphous materials occur among the condensed phosphates. 

Pyrophosphates. The simplest linear condensed phosphates are pyrophosphates, which can be considered as the dehydration product of two orthophosphate groups. A water molecule is eliniinated to form a P—O—P linkage in a reversible reaction. 

In most analytical procedures for determining the total phosphoms content (normally expressed in terms of P20 ), the phosphates are converted to the orthophosphate form. Typically, condensed phosphates are hydrolyzed to orthophosphate by boiling in dilute mineral acid (0.1 N). The orthophosphate is then deterrnined by gravimetric or spectrophotometric methods. For gravimetric deterrnination, insoluble phosphomolybdates (or magnesium ammonium orthophosphate) is formed. 

The general manufacturing scheme for phosphate salts is shown in Figure 11. Condensed phosphates are prepared from the appropriate orthophosphate or mixture of orthophosphates, so the preparation of orthophosphates must be considered first for the manufacture of any phosphate salt. Phosphoric acid is neutralized to form a solution or slurry with a carefully adjusted acid/base ratio according to the desired orthophosphate product. The orthophosphate may be recovered either by crystallization from solution, or the entire solution or slurry may be evaporated to dryness. The dewatering (qv) method is determined by the solubihty properties of the product and by its desired physical properties such as crystal size and shape, bulk density, and surface area. Acid orthophosphate salts may be converted to condensed phosphates by thermal dehydration (calcination). 

Condensed Phosphates. The term condensed phosphate refers to any dehydrated, condensed orthophosphate for which the M20 P20 ratio is less than 3 1 (17). (1) is disodium orthophosphate [7558-79-4] and (2) tetrasodium pyrophosphate [7722-88-5]. 

A. Molybdenum blue method Discussion. Orthophosphate and molybdate ions condense in acidic solution to give molybdophosphoric acid (phosphomolybdic acid), which upon selective reduction (say, with hydrazinium sulphate) produces a blue colour, due to molybdenum blue of uncertain composition. The intensity of the blue colour is proportional to the amount of phosphate initially incorporated in the heteropoly acid. If the acidity at the time of reduction is 0.5M in sulphuric acid and hydrazinium sulphate is the reductant, the resulting blue complex exhibits maximum absorption at 820-830 nm. 

Some phosphates are simple orthophosphates, whereas others are condensed phosphates. Polymeric forms are also available these are complex condensed polyphosphates, all of which may be present in hydrogen, sodium, potassium, or even ammonium form. 

Condensation of CO2, ammonia, and ATP to form carbamoyl phosphate is catalyzed by mitochondrial carbamoyl phosphate synthase I (reaction 1, Figure 29-9). A cytosolic form of this enzyme, carbamoyl phosphate synthase II, uses glutamine rather than ammonia as the nitrogen donor and functions in pyrimidine biosynthesis (see Chapter 34). Carbamoyl phosphate synthase I, the rate-hmiting enzyme of the urea cycle, is active only in the presence of its allosteric activator JV-acetylglutamate, which enhances the affinity of the synthase for ATP. Formation of carbamoyl phosphate requires 2 mol of ATP, one of which serves as a phosphate donor. Conversion of the second ATP to AMP and pyrophosphate, coupled to the hydrolysis of pyrophosphate to orthophosphate, provides the driving... 

One example is silicate cement where orthosilicic acid, chemically generated in solution, condenses to form a silicic acid gel. Another is refractory cement where a cementitious product is formed by the heat treatment of an acid orthophosphate, a process which again involves condensation to form a polyphosphate. 

Orthopedic devices, 3 721-735 joint replacement, 3 727-735 Orthopedic marrow needles, 3 743-744 Orthophosphate (PO4), in soil, 11 112 Orthophosphates, 18 830-841 20 637 magnesium, 18 839 manufacture of, 18 853-855 Orthophosphate salts, 18 836 Orthophosphoric acid, 18 815, 817-826 condensation of, 18 826 properties of, 18 817-819 solubility of boron halides in, 4 140t orf/zo-phthalic resins, 20 101, 113 formulation of, 20 102 Orthorhombic crystal system, 8 114t Orthorhombic phosphorus pentoxide, 19 49 Orthorhombic structure, of ferroelectric crystals, 11 95, 96 Orthorhombic symmetry, 8 114t Orthosilicate monomers, in silicate glasses, 22 453... 

Condensed (poly) phosphates may exert different effects on calcium utilization than the aforementioned effects of simple (ortho-) phosphates. Polyphosphates have a much greater affinity for calcium than do orthophosphates, and soluble calcium-polyphosphate complexes are readily formed in the gastric and intestinal environments. In addition, polyphosphates must be hydrolyzed by an intestinal alkaline phosphatase (27) prior to absorption. We have found polyphosphates to be incompletely (80.5%) hydrolyzed to orthophosphate during the digestive process in young adult males when calcium intake was low only 56% of a 1 g phosphorus supplement was absorbed from a polyphosphate sources as compared to 71% from an orthophosphate source (5). 

Crystalline polyammonium catena-polyphosphate, (NH4) H2P 03 + 1, has been prepared by heating urea and monoammonium orthophosphate under ammonia vapor for 16 hours,1 by ammoniation of superphosphoric acid,2 by thermal condensation of urea phosphate,3 and by heating various ammonium phosphates in a current of ammonia.4,5 The procedure given below, in which crude ammonium tetrametaphosphate is reorganized and condensed to a long-chain polymer in a stream of ammonia, is straightforward and permits the use of common laboratory equipment and supplies. 

Orthophosphate and condensed phosphate are a measure of inorganic phosphoms. The latter is also termed as acid-hydrolyzable phosphate. However, during mild acid hydrolysis, a small amount of phosphoms from organic phosphoms compounds may be released. To determine suspended and dissolved forms of phosphoms, the sample should be filtered through a 0.45 pm membrane filter, and the filtrate and the residue analyzed separately. 

Belozersky, 1958,1959 Konovalov, 1960) or 10 % perchloric acid, at 80-100 °C (Krishnan etal, 1957 Drews, 1960b Fedorov, 1961 Harold, 1960,1962ab lames andCasida, 1964). When this method of extraction was employed, the condensed phosphates are hydrolysed to orthophosphate, the amount of which indicates the amount of condensed phosphates present in the acid-insoluble fraction. Hughes and co-workers (Hughes et al, 1963) used a prolonged (5 h) extraction of acid-insoluble PolyPs with 10 % TCA at 20-22 °C. In the author s opinion, this method ensures an almost complete extraction of acid-insoluble PolyPs from the cells of bacteria and other microorganisms. 

L. A. Okorokov, L. P. Lichko and I. S. Kulaev (1973a). A comparative investigation of the functions of polymeric metal orthophosphates and condensed polyphosphates in Penicillium chrysogenum (in Russian). Izv. Akad. Nauk SSSR. Ser. Biol., 1, 86-89. 

The cheapest and most important salts of purified phosphoric acid are the sodium salts, made by reacting the acid with sodium carbonate or sodium hydroxide. Sodium phosphates may be classified in a general way as (1) orthophosphates, (2) crystalline condensed phosphates, and (3) glassy condensed phosphates. 

Condensed phosphates are made by eliminating water from orthophosphates. The most important compound is sodium tripolyphosphate (STPP), made according to the following reaction ... 

Inorganic polyphosphates (polyPs), also called condensed phosphates, are linear polymers of tetrahedral orthophosphate units linked through common oxygen atoms by phosphoanhydride bonds (Figure 1A). PolyPs can be formed in the laboratory or in nature by temperature- or pressure-induced condensation of acid orthophosphate salts accordingly, they are prepared synthetically by heating the... 

The enzymic condensation of enolpyruvate phosphate and n-erythrose 4-phosphate is formulated in Fig. 4 as an attack by a nucleophilic group of the enzyme (here symbolized as OH ) on the enolphosphate, concerted with attack by carbon atom 3 of the enolpyruvate on the electrophilic carbon atom of the aldehyde, and protonation of the carbonyl oxygen atom by an acidic group. This results in the release of orthophosphate, or of a transient, phosphorylated enzyme, and the open-chain form of 3-deoxy-n-orobfno-heptulosonic acid 7-phosphate. In this mechanism, enolpyruvate phosphate could be replaced by an enolpyruvate-enzyme compound. The reaction is analogous to the irreversible reaction for the fixation of carbon dioxide (Reaction 7), found in plants, in which intermediates could also Enolpyruvate phosphate -f HCOi - oxaloacetate + HPO< (7)... 

In the third pathway for the formation of 3-deoxyulosonic acids, enol pyruvate phosphate and an aldose phosphate are condensed, yielding orthophosphate and a 3-deoxyulosonic acid phosphate. In addition to formation of 3-deoxy-n-araInno-heptulosonic acid 7-phosphate, another example of this type of reaction is the formation of a 3-deoxyoctulosonic acid 8-phosphate (probably 3-deoxy-D-jfJMCo-octulosonic acid) from enolp3Tmvate phosphate and D-arabinose 5-phosphate. These reactions, unlike those involving pjrruvate, proceed completely to the right and have, so far, not been reversed. 

Condensed phosphates are usually prepared by dehydration of orthophosphates under various conditions of temperature (300-1200°C) and also by appropriate... 

Orthophosphates are monomers. Their condensation polymerization leads to compounds such as pyrophosphates or metaphosphates, which have structures of long chain or ring polymers. These phosphates are formed by linkages of PO4 tetrahedra with shared oxygen atoms, such that the skeletons with alternating P and O atoms, either in chains or rings, are formed by heat treatment of orthophosphates, as in the following example ... 

In addition to the orthophosphates, other rare earth phosphates could also be obtained through hydrothermal routes. Tang et al. reported the synthesis of so-called CeP (with a composition of Ce(FIP04)2" H2O) nanotubes (Tang et al., 2005c). Concentrated phosphoric acid solution of 6 M was heated to a temperature ranging from 50 to 110 °C to form a condensed lirrear polyphosphate (P 03 +i) +2 Then, the (NH4)2Ce(N03)e solution is... 

Phosphates are compoimds that contain oxyanions of phosphorus(V), ranging from the simple orthophosphate group to condensed chain, ring, and network anions. Oxyanions of phosphorus in lower oxidation states such as phosphite, HP03, are also known. 

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