Phosphoric acid Subject

Devising an economical method of producing agricultural-grade potassium phosphates from potassium chloride and wet-process phosphoric acid has been the subject of intense agricultural—chemical research (37—39). Limited quantities have been produced industrially. The impact on the overall quantities of phosphoms and potassium compounds consumed by the fertilizer industry is small. Because potassium phosphates are an excellent source of two essential fertilizer elements, this research is expected to continue. 

For commercial appHcation, catalyst activity is only one of the factors to be considered. Equally important is catalyst life, but Htde has been pubHshed on this aspect. Partly because of entrainment losses and partly through loss of acid as volatile triethyl phosphate, the catalyst loses activity unless compensating steps are taken. This decline in activity can be counteracted by the periodic or continuous addition of phosphoric acid to the catalyst during use, a fact that seems to have been disclosed as early as 1940 (94). A catalyst subjected periodically to acid addition could remain in service indefinitely, according to a report by Shell (91). A later Shell patent (85) states that complete reimpregnation with acid is required every 200 mn-days. 

B. Solvolysis of Phosphoric Acid Derivatives.—Interest continues in neighbouring-group participation in the solvolysis of phosphate esters. As a potential model compound for investigating the mechanism of ribo-nuclease action, the phenyl hydrogen phosphate ester of c/j-3,4-tetrahydro-furandiol (24) has been the subject of a detailed study. Above (and probably also below) pH 4 hydrolysis gives solely the cyclic phosphate (25)... 

Cochineal pigments are extracted from dried bodies of female insects with water or with ethanol the result is a red solution that is concentrated in order to obtain the 2 to 5% carminic acid concentration customary for commercial cochineal. For carmine lakes, the minimum content of carminic acid is 50%. An industrial procedure applied in Spain uses ammonium hydroxide as the extracting agent and phosphoric acid as the acidifying agent. For analytical purposes the extraction is carried out with 2 N HCl at 100°C. The chemical synthesis of carminic acid has also been reported and is the subject of European and United States patents. ... 

In the 1870s more effective liquid cement-formers were found ortho-phosphoric acid and eugenol (Wilson, 1978). It was also found that an aluminosilicate glass could replace zinc oxide, a discovery which led to the first translucent cement. Thereafter the subject stagnated until the late 1960s when the polyelectrolyte cements were discovered by Smith (1968) and Wilson Kent (1971). 

Nucleic acids, DNA and RNA, are attractive biopolymers that can be used for biomedical applications [175,176], nanostructure fabrication [177,178], computing [179,180], and materials for electron-conduction [181,182]. Immobilization of DNA and RNA in well-defined nanostructures would be one of the most unique subjects in current nanotechnology. Unfortunately, a silica surface cannot usually adsorb duplex DNA in aqueous solution due to the electrostatic repulsion between the silica surface and polyanionic DNA. However, Fujiwara et al. recently found that duplex DNA in protonated phosphoric acid form can adsorb on mesoporous silicates, even in low-salt aqueous solution [183]. The DNA adsorption behavior depended much on the pore size of the mesoporous silica. Plausible models of DNA accommodation in mesopore silica channels are depicted in Figure 4.20. Inclusion of duplex DNA in mesoporous silicates with larger pores, around 3.8 nm diameter, would be accompanied by the formation of four water monolayers on the silica surface of the mesoporous inner channel (Figure 4.20A), where sufficient quantities of Si—OH groups remained after solvent extraction of the template (not by calcination). 

Several allotropic forms of phosphorus are known, the most common of which are the white, red, and black forms. Heating the white form at 400 °C for several hours produces red phosphorus, which is known to include several forms. A red form that is amorphous can be prepared by subjecting white phosphorus to ultraviolet radiation. In the thermal process, several substances (I2, S8, and Na) are known to catalyze the conversion of phosphorus to other forms. Black phosphorus consists of four identifiable forms that result when white phosphorus is subjected to heat and pressure. Phosphorus is used in large quantities in the production of phosphoric acid and other chemicals. White phosphorus has been used extensively in making incendiary devices, and red phosphorus is used in making matches. 

A mixture of 6-aminocaproic acid (13 g, 0.1 mol) and phosphorous acid (12.7 g, 0.156 mol) in chlorobenzene (100 ml) was heated to 100°C with stirring. Phosphorus trichloride (22 g, 0.16 mol) was added drop-wise to the mixture within a period of 30 min. The solution was then heated with stirring for 3 h. Insoluble material separated during this time. After cooling, the solvent was decanted, and the residue was boiled with water (60 ml) for 30 min and subjected to hot filtration with activated charcoal through a layer of Supercel. The solution was concentrated under reduced pressure and the crystals formed were collected by filtration. Methanol was added to the mother liquors to complete the precipitation. There was in this way isolated pure 6-amino-l-hydroxyhexylidenediphosphonic acid (15 g, 55%) of mp 245°C. 

To test the hypothesis that the addition of CCM reduces dental erosion, the erosive effects of four different drinks was compared a citric acid-based orange-flavored soft drink fortified with CCM (pH 4.0, 1344 mg Ca/liter) the same drink without CCM (pH 3.6, 72 mg Ca/liter) and positive and negative controls consisting of a diet phosphoric acid-based cola (pH 3.1, 35 mg Ca/liter) and distilled water, respectively (Rugg-Gurm et ah, 1998). In a randomized cross-over design comprised of four 6-day periods, 11 subjects were required to wear a palatal... 

Chlorothietane was subjected to reaction with dichloro derivatives of phosphorous acid to give, after heating the reaction mixture to 150°C, the acyclic compound thiophosphoric acid in low yields. ... 

System (4) has been reported for the quantitative determination of steroids in health and disease [143], Prior to analysis, free steroids were removed from the sample. Conjugated steroids were enzymatically hydrolyzed, and the liberated products extracted into 1 3 tetrahydrofuran-ethyl ether. The extract was evaporated, the residue dissolved in acetic acid, and then oxidized with sodium bismuthate. The final product was acetylated or formulated, and subjected to GC analysis along with the standard. A stabilized column of 4% LAC-2R-446 and 1% 85% phosphoric acid on... 

System (8) has been described for quantitation of corticosteroids as common adulterants in local drugs [156]. The sample is extracted from its matrix by methanol, and the resulting supernatant layer subjected to the HPLC analysis. The column used was an ODS-Zorbax column (25 cm x 4.6 mm), and the mobile phase 7 2 11 acetonitrile-methanol-aqueous 1% phosphoric acid. An eluent flow rate of 0.8 mL/min was used, and the analyte detection was performed using the UV absorbance at 240 nm. The calibration graph was found to be linear in the ranges of 1-15 pg/mL for betamethasone, 0.5-20 pg/mL for prednisolone, and 1-30 pg/mL for cortisone acetate. 

Chlorine atoms were produced by flowing a mixture of 5 % Cl2 in helium through a quartz tube, coated with a thin film of baked phosphoric acid to inhibit Cl atom recombination, and enclosed in a 2.45 GHz microwave cavity operating at 35 W. The purity of reactants was 99.5 to 97 %, and they were frequently subjected to several freeze-pump-thaw cycles. The reactants were flowed inside the reactor neat or diluted in helium (3% mixtures). 

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