Phosphorous, determination

Black lamps A black lamp is a low-pressure mercury lamp whose envelope is covered with a phosphor such as strontium fluoroborate or barium disilicate. The type of phosphor determines the spectral distribution of the lamp output (Forbes et al., 1976). Figure 16.4 shows a typical spectral distribution for A < 500 nm from a black lamp as well as the solar... 

Edmond Becquerel (1820-1891) was the nineteenth-century scientist who studied the phosphorescence phenomenon most intensely. Continuing Stokes s research, he determined the excitation and emission spectra of diverse phosphors, determined the influence of temperature and other parameters, and measured the time between excitation and emission of phosphorescence and the duration time of this same phenomenon. For this purpose he constructed in 1858 the first phosphoroscope, with which he was capable of measuring lifetimes as short as 10-4 s. It was known that lifetimes considerably varied from one compound to the other, and he demonstrated in this sense that the phosphorescence of Iceland spar stayed visible for some seconds after irradiation, while that of the potassium platinum cyanide ended after 3.10 4 s. In 1861 Becquerel established an exponential law for the decay of phosphorescence, and postulated two different types of decay kinetics, i.e., exponential and hyperbolic, attributing them to monomolecular or bimolecular decay mechanisms. Becquerel criticized the use of the term fluorescence, a term introduced by Stokes, instead of employing the term phosphorescence, already assigned for this use [17, 19, 20], His son, Henri Becquerel (1852-1908), is assigned a special position in history because of his accidental discovery of radioactivity in 1896, when studying the luminescence of some uranium salts [17]. 

PTV-GC with a nitrogen-phosphorous determination recovery. >95% (86% for tri(n-butyl) phosphate) extracted fraction-. 

ETA-LEAFS with direct solid analysis using an excimer laser (308 nm) was used to measure phosphorous in PET over a wide range (2-3000 Mgg ) with fg detection limits and a standard deviation of about 10% [116] validation by ETAAS and ICP-AES. A comparison of the detection limits obtained by ETA-LEAFS with commonly used techniques for phosphorous determinations is presented in Table 3.15. 

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). 

The identity of the moiety (other than glycerol) esterified to the phosphoric group determines the specific phosphoHpid compound. The three most common phosphoHpids in commercial oils are phosphatidylcholine or lecithin [8002-45-5] (3a), phosphatidylethanolamine or cephalin [4537-76-2] (3b), and phosphatidjlinositol [28154-49-7] (3c). These materials are important constituents of plant and animal membranes. The phosphoHpid content of oils varies widely. Laurie oils, such as coconut and palm kernel, contain a few hundredths of a percent. Most oils contain 0.1 to 0.5%. Com and cottonseed oils contain almost 1% whereas soybean oil can vary from 1 to 3% phosphoHpid. Some phosphoHpids, such as dipaLmitoylphosphatidylcholine (R = R = palmitic R" = choline), form bilayer stmetures known as vesicles or Hposomes. The bdayer stmeture can microencapsulate solutes and transport them through systems where they would normally be degraded. This property allows their use in dmg deHvery systems (qv) (8). 

The total phosphoms content of the sample is determined by method AOCS Ja 5-55. Analysis of phosphoUpid in lecithin concentrates (AOCS Ja 7-86) is performed by fractionation with two-dimensional thin-layer chromatography (tic) followed by acid digestion and reaction with molybdate to measure total phosphorous for each fraction at 310 nm. It is a semiquantitative method for PC, PE, PI, PA, LPC, and LPE. Method AOCS Ja 7b-91 is for the direct deterrnination of single phosphoHpids PE, PA, PI, PC in lecithin by high performance Hquid chromatography (hplc). The method is appHcable to oil-containing lecithins, deoiled lecithins, lecithin fractions, but not appHcable to lyso-PC and lyso-PE. 

Phospholipids. Phospholipids, components of every cell membrane, are active determinants of membrane permeabiUty. They are sources of energy, components of certain enzyme systems, and involved in Hpid transport in plasma. Because of their polar nature, phosphoUpids can act as emulsifying agents (42). The stmcture of most phosphoUpids resembles that of triglycerides except that one fatty acid radical has been replaced by a radical derived from phosphoric acid and a nitrogen base, eg, choline or serine. 

However, the peroxomonophosphate ion decomposes relatively rapidly ia aqueous solution. A mixture of peroxodiphosphoric and peroxomonophoshoric acids can be produced by treatiag a cold phosphoric acid solution with elemental fluorine (qv) (49). Peroxodiphosphoric acid is not produced commercially. Ammonium, lithium, sodium, potassium, mbidium, cesium, barium, 2iac, lead, and silver salts have all been reported. The crystal stmctures of the ammonium, lithium, sodium, and potassium compounds, which crysta11i2e with varyiag numbers of water molecules, have been determined (50). 

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). 

For the bones the preferenee has been given to atomie-absorption speetrometry with flame and graphite furnaee atomization beeause of a strong effeet of ealeium and phosphorous on the analytieal signals of mieroelements under determination in DCP-ai e AFS. It has been shown that In the presenee of lanthanum ehloride no interferenee effeets were observed in flame AAS for Ca, Mg and Sr. FTA AAS has been used to determine Mn and Li in bones. RSD for FAAS determination of Ca, Mg, Sr were 3-6 %, as for Li and Mn -10-12%. 

The press had been designed with a capacity to deliver 280 kN press force and to work at a production rate of 40 lids per minute. Calculations to determine the distribution of forming loads required indicated that the press capacity was adequate to form the family of steel lids to be produced on the machine. One of the major areas of interest in the design was the con-rod and pin (see Figure 4.66). The first option considered was based on a previous design where the con-rod was manufactured from cast iron with phosphor bronze bearings at the big and small ends. However, weaknesses in this approach necessitated the consideration of other options. The case study presents the analysis of the pin and con-rod using simple probabilistic techniques in an attempt to provide in-service reliable press operation. The way a weak link was introduced to ensure ease of maintenance and repair in the event... 

Rider and Amott were able to produce notable improvements in bond durability in comparison with simple abrasion pre-treatments. In some cases, the pretreatment improved joint durability to the level observed with the phosphoric acid anodizing process. The development of aluminum platelet structure in the outer film region combined with the hydrolytic stability of adhesive bonds made to the epoxy silane appear to be critical in developing the bond durability observed. XPS was particularly useful in determining the composition of fracture surfaces after failure as a function of boiling-water treatment time. A key feature of the treatment is that the adherend surface prepared in the boiling water be treated by the silane solution directly afterwards. Given the adherend is still wet before immersion in silane solution, the potential for atmospheric contamination is avoided. Rider and Amott have previously shown that such exposure is detrimental to bond durability. 

When, in the phosphorous oxychloride-pyridine dehydration of an alcohol these rules conflict, the stereoelectronic factor determines the direction of elimination ... 

Less Less Flow Excess ammonia in reactor. Release to work area, with amount released related to quantitative reduction in supply. Team member to calculate toxicity vs. flow reduction. 1. Valve A partially closed. 2. Partial plug or leak in pipe. Automatic closure of valve B on reduced flow from phosphoric acid supply. Set point determined by toxicity vs. flow calculation. 

On an industrial scale PCI3 is sprayed into steam at 190 and the product sparged of residual water and HCl using nitrogen at 165. Phosphorous acid forms colourless, deliquescent crystals, mp 70. T, in which the structural units shown form four essentially linear H bonds (O - H 155-I60pm) which. stabilize a complex 3D network. The molecular dimensions were determined by low-temperature single-crystal neutron diffraction at 15K.f - ... 

Phosphor-athcr, m. phosphoric ether (ester of phosphoric acid, specif, ethyl phosphate), -basis, phosphorus base, -bestimmung, /. determination of phosphorus, -blei, n. lead phosphide Min.) pyromorphite. -bombe, f. phosphorus bomb. -brandgranate, /. phosphorus incendiary shell, -brei, m. phosphorus paste, -bromid, n. phosphorus bromide, specif, phosphorus pentabromide, phos-phorus(V) bromide, -bromijr, n. phosphorus tribromide, phosphorus(III) bromide, -bronze, /. phosphor bronze, -calcium, n. calcium phosphide, -chlorid, n. phosphorus chloride, specif, phosphorus pcntachloride, phosphorus(V) chloride, -chloriir, n. phosphorous chloride (phosphorus trichloride, phosphorus(III) chloride), -dampf, tn. phosphorus vapor or fume, -eisen, n. ferrophos-phorus iron phosphide, -eisensinter, m. diadochite. 

The work of Porter et al. has shown that for copper in phosphoric acid the interfacial temperature was the main factor, and furthermore this was the case for positive or negative heat flux. Activation energies were determined for this system they indicated that concentration polarisation was the rate-determining process, and by adjustment of the diffusion coefficient and viscosity for the temperature at the interface and the application of dimensional group analysis it was found that ... 

This input to design refers to the long-term stability of the raw material sources for the plant. It is only of importance where the raw materials can or do contain impurities which can have profound effects on the corrosivity of the process. Just as the design should cater not only for the norm of operation but for the extremes, so it is pertinent to question the assumptions made about raw material purity. Crude oil (where HjS, mercaptan sulphur and napthenic acid contents determine the corrosivity of the distillation process) and phosphate rock (chloride, silica and fluoride determine the corrosivity of phosphoric acid) are very pertinent examples. Thus, crude-oil units intended to process low-sulphur crudes , and therefore designed on a basis of carbon-steel equipment, experience serious corrosion problems when only higher sulphur crudes are economically available and must be processed. 

The relation between free phosphoric acid content and total phosphate content in a processing bath, whether based on iron, manganese or zinc, is very important this relation is generally referred to as the acid ratio. An excess of free acid will retard the dissociation of the primary and secondary phosphates and hinder the deposition of the tertiary phosphate coating sometimes excessive loss of metal takes place and the coating is loose and powdery. When the free acid content is too low, dissociation of phosphates (equations 15.2, 15.3 and 15.4) takes place in the solution as well as at the metal/solution interface and leads to precipitation of insoluble phosphates as sludge. The free acid content is usually determined by titrating with sodium... 

For the primary stage (phosphoric) V) acid as a monoprotic acid), methyl orange, bromocresol green, or Congo red may be used as indicators. The secondary stage of phosphoric) V) acid is very weak (see acid Ka = 1 x 10 7 in Fig. 10.4) and the only suitable simple indicator is thymolphthalein (see Section 10.14) with phenolphthalein the error may be several per cent. A mixed indicator composed of phenolphthalein (3 parts) and 1-naphtholphthalein (1 part) is very satisfactory for the determination of the end point of phosphoric(V) acid as a diprotic acid (see Section 10.9). The experimental neutralisation curve of 50 mL of 0.1M phosphoric(V) acid with 0.1M potassium hydroxide, determined by potentiometric titration, is shown in Fig. 10.6. 

Procedure. To obtain experience in the method, the purity of analytical-grade potassium chlorate may be determined. Prepare a 0.02M potassium chlorate solution. Into a 250 mL conical flask, place 25.0 mL of the potassium chlorate solution, 25.0mL of 0.2M ammonium iron(II) sulphate solution in 2M sulphuric acid and add cautiously 12 mL concentrated sulphuric acid. Heat the mixture to boiling (in order to ensure completion of the reduction), and cool to room temperature by placing the flask in running tap water. Add 20 mL 1 1 water/phosphoric(V) acid, followed by 0.5 mL sodium diphenyl-amine-sulphonate indicator. Titrate the excess Fe2+ ion with standard 0.02M potassium dichromate to a first tinge of purple coloration which remains on stirring. 

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