Silica phosphatization

In Germany, a silica-phosphate glass-ceramic has been developed and used clinically. It consists of fluorhydroxyapatite (Caio(P04)e(OH,F)2) and phlogopite ((Na,K)Mg3(AISi30io)F2), a type of mica [88,94-96],... 

Fig. 9.8. Comparison of pressure supported CEC (only the inlet vial is pressurized) and HPLC enantiomer separation of mephobarbital. Conditions 100 pm I.D. x 23.5 cm capillary (overall length, 40 cm) packed with Chira-Dex-silica phosphate buffer (5 mM, pH 7.0)-methanol (4 1, v/v) UV detection, 230 nra CEC, 20 kV 10 bar HPLC, 140 bar. Reproduced from [42], with permission.

This dissociated zircon is amenable to hot aqueous caustic leaching to remove the silica in the form of soluble sodium silicate. The remaining skeletal stmcture of zirconia is readily washed to remove residual caustic. Purity of this zirconia is direcdy related to the purity of the starting zircon since only silica, phosphate, and trace alkalies and alkaline earth are removed during the leach. This zirconia, and the untreated dissociated zircon, are both proposed for use ia ceramic color glazes (36) (see Colorants for ceramics). 

The simplest version of the iron (III) coagulation-microflltration process is by nature more complex and costly than the simplest versions of the ion-exchange and metal-oxide adsorbent processes. Furthermore, as is the case with the MOA processes, high feed pH, and the presence of signiflcant silica, phosphate, and fluoride concentrations will decrease the arsenic-removal efficiency of the C-MF process. Nevertheless, C-MF is attractive for arsenic removal because of lower chemical consumption and less waste production. 

The process variables known to influence arsenic capacity and column performance of alumina, GFH, and other adsorbents are as follows adsorbent, adsorbent particle size, flow rate, EBCT, and water quality parameters including arsenic concentration, As(III)/(V) speciation, pH, silica, phosphate, fluoride, hardness, and sulfate concentrations. Even with a complete water analysis, it is prudent to perform pilot studies with competitive adsorbents on the water to be treated because of the numerous factors that influence arsenic adsorption. Equilibrium isotherms and rapid small-scale column tests (RSSCTs) are typically run prior to the pilot study (7). 

A strong rock-like material is reported to be obtainable from furnace slag, lime and portland cement [56a], A useful material ( silica phosphate ) can be obtained by heating silica sand and phosphoric acid to around 1200°C. It is claimed the product has high strength and low porosity, and is lightweight and acid resistant [57]. 

This is an acid-base reaction, in which the base is the oxide ion (p. 89) the acidic oxide SiOj displaces the weaker acidic oxide CO2 in the fused mixture. But in aqueous solution, where the 0 ion cannot function as a strong basefp. 89),carbon dioxide displaces silica, which, therefore, precipitates when the gas is passed through the aqueous silicate solution. In a fused mixture of silica and a nitrate or phosphate, the silica again displaces the weaker acidic oxides N2O5 and P4OJ0 ... 

White phosphorus may be made by several methods. By one process, tri-calcium phosphate, the essential ingredient of phosphate rock, is heated in the presence of carbon and silica in an electric furnace or fuel-fired furnace. Elementary phosphorus is liberated as vapor and may be collected under phosphoric acid, an important compound in making super-phosphate fertilizers. 

Ethyl o-nitrocinnamate (1 mmol) was dissolved in triethyl phosphite (5 mmol) and heated at 170°C for 3 h. The triethyl phosphite and triethyl phosphate were removed in vacuo. The residue w as eluted through a column of silica gel using CHCI3 and the product recrystallizcd from CHCl3-hexane. The yield was 94%. 

Na2C03 851 Ft For silicates, and silica-containing samples alumina-containing samples insoluble phosphates and sulfates... 

Mineral Feed. Mineral feed supplements for domestic animals and fowl usually contain a pure form of pulverized limestone. In fact, some state laws require the supplement to be at least 35% available calcium. Other sources of calcium are bone meal and dicalcium phosphate. Use as mineral feed has been a steadily growing market for limestone. The material is ground to 90% minus 0.15 mm (100 mesh) or 80% minus 0.9074 mm (200 mesh), is low in silica, and has strict tolerances on arsenic and fluorine (see Feeds and feed additives). 

Coesite. Coesite, the second most dense (3.01 g/cm ) phase of silica, was first prepared ia the laboratory by heating a mixture of sodium metasibcate and diammonium hydrogen phosphate or another mineraliser at 500—800°C and 1.5—3.5 GPa (14,800—34,540 atm). Coesite has also been prepared by oxidation of silicon with silver carbonate under pressure (67). The stmcture is monoclinic = 717 pm, Cg = 1.238 pm, and 7 = 120°. 

An abrasive is usually chemically inert, neither interacting with other dentifrice ingredients nor dissolving in the paste or the mouth. Substances used as dentifrice abrasives include amorphous hydrated silica, dicalcium phosphate dihydrate [7789-77-7] anhydrous dicalcium phosphate [7757-93-9] insoluble sodium metaphosphate [10361-03-2], calcium pyrophosphate [35405-51-7], a-alumina trihydrate, and calcium carbonate [471-34-1]. These materials are usually synthesized to specifications for purity, particle size, and other characteristics naturally occurring minerals are used infrequently. Sodium bicarbonate [144-55-8] and sodium chloride [7647-14-5] have also been employed as dentifrice abrasives. 

Typical applications include primary devv atering of phosphate rock matrix and silica sand products following vv et screening. In ore dressing it is used rnainlv to protect large-diameter thickeners bv scalping out-l-65-mesh material,... 

Typical applications include careful sizing of silica-glass sand, washing phosphate rock, sizing of abrasives, smokeless powder, sodium ahi-rninate, etc,... 

Triboeleetrie Silica from limestone Florida pebble-phosphate flotation cone. Reduction of (piartz bv 80-90% Residual silica from pebble phosphate Tube t pe Tube t pe 80-100 70-90 -1.0 + 0.015 -1.0 + 0.10 20 10-15 1 1... 

Strong acids are able to donate protons to a reactant and to take them back. Into this class fall the common acids, aluminum hahdes, and boron trifluoride. Also acid in nature are silica, alumina, alumi-nosihcates, metal sulfates and phosphates, and sulfonated ion exchange resins. They can transfer protons to hydrocarbons acting as weak bases. Zeolites are dehydrated aluminosilicates with small pores of narrow size distribution, to which is due their highly selective action since only molecules small enough to enter the pores can reacl . 

Of the phosphorus-containing polymers the polyphosphates have been known for many years. Aluminium phosphate had been used in the manufacture of heat-resistant silica-fibre-reinforced laminates. 

Triphenyl phosphate Tripoli, see Silica, crystalline Tungsten as W... 

It is known that not all reactions proceed in the same manner on all adsorbent layers because the material in the layer may promote or retard the reaction. Thus, Ganshirt [209] was able to show that caffeine and codeine phosphate could be detected on aluminium oxide by chlorination and treatment with benzidine, but that there was no reaction with the same reagent on silica gel. Again the detection of amino acids and peptides by ninhydrin is more sensitive on pure cellulose than it is on layers containing fluorescence indicators [210]. The NBP reagent (. v.) cannot be employed on Nano-Sil-Ci8-100-UV2S4 plates because the whole of the plate background becomes colored. 

For the size exclusion chromatography of proteins on silica-hased diol packings, it is generally recommended to use fully aqueous mobile phases with a salt concentration between 0.1 and 0.3 M. In general, a phosphate buffer around pH 7 is used as the mobile phase. Under these circumstances, the tertiary structure of most proteins is preserved without difficulty and the interaction of proteins with each other is minimized. However, other inorganic buffers or combinations of buffers with organic solvents can be used without difficulties for special applications. 

A typical modem phosphorus fumace (12 m diameter) can produce some 4 toniKs per hour and is rated at 60-70 MW (i.e. 140000A at SOOV). Three electrodes, each weighing 60 tonnes, lead in the current. The amounts of raw material required to make 1 tonne of white phosphorus depend on their purity but are typically 8 tonnes of phosphate rock. 2 tonnes of silica, 1.5 tonnes of coke, and 0.4 tonnes of electrode carbon. The phos rfKmis vapour is driven off from the top of the fumace together with the CO and some H2 it is passed through a hot electrostatic precipitator to remove dust and then condensed by water sprays at about 70 (P4 melts at 44.T). The byproduct CO is used for supplementary heating. 

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