Home About us Contact
|
Home About us Contact | ||
|
|
||
Sulphuric Acid (sulphuric + acid)
Selected AbstractsThe effect of organic acids on base cation leaching from the forest floor under six North American tree speciesEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2001F. A. Dijkstra Summary Organic acidity and its degree of neutralization in the forest floor can have large consequences for base cation leaching under different tree species. We investigated the effect of organic acids on base cation leaching from the forest floor under six common North American tree species. Forest floor samples were analysed for exchangeable cations and forest floor solutions for cations, anions, simple organic acids and acidic properties. Citric and lactic acid were the most common of the acids under all species. Malonic acid was found mainly under Tsuga canadensis (hemlock) and Fagus grandifolia (beech). The organic acids were positively correlated with dissolved organic carbon and contributed significantly to the organic acidity of the solution (up to 26%). Forest floor solutions under Tsuga canadensis contained the most dissolved C and the most weak acidity among the six tree species. Under Tsuga canadensis we also found significant amounts of strong acidity caused by deposition of sulphuric acid from the atmosphere and by strong organic acids. Base cation exchange was the most important mechanism by which acidity was neutralized. Organic acids in solution from Tsuga canadensis, Fagus grandifolia, Acer rubrum (red maple) and Quercus rubra (red oak) were hardly neutralized while much more organic acidity was neutralized for Acer saccharum (sugar maple) and Fraxinus americana (white ash). We conclude that quantity, nature and degree of neutralization of organic acids differ among the different tree species. While the potential for base cation leaching with organic acids from the forest floor is greatest under Tsuga canadensis, actual leaching with organic anions is greatest under Acer saccharum and Fraxinus americana under which the forest floor contains more exchangeable cations than does the strongly acidified forest floor under Tsuga canadensis. [source] Novel synthesis of flavour quality , -lactonesFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2006Dhananjay D. Zope Abstract The cyclization of 3-alkenoic acids with 80% sulphuric acid in the synthesis of , -lactones is always associated with fumes of sulphur dioxide gas and traces of cyclopentenones. The cyclopentenones formed during the reaction give off-odours to the , -lactones formed. Two catalysts, p -toluene sulphonic acid and o -phosphoric acid, with a catalytic amount of perchloric acid, were tried in the lactonization reaction to obtain , -lactones in high yields, and the reaction was free from sulphur dioxide gas fumes and cyclopentenones. A comparison of these catalysts with 80% sulphuric acid in the synthesis of , -lactones was also made. Copyright © 2006 John Wiley & Sons, Ltd. [source] Invasion of a karst aquifer by hydrothermal fluids: evidence from stable isotopic compositions of cave mineralizationGEOFLUIDS (ELECTRONIC), Issue 2 2001S. H. Bottrell Abstract Mineral deposits in the Cupp-Coutunn/Promeszutochnaya cave system (Turkmenia, central Asia) record a phase of hydrothermal activity within a pre-existing karstic groundwater conduit system. Hydrothermal fluids entered the caves through fault zones and deposited sulphate, sulphide and carbonate minerals under phreatic conditions. Locally, intense alteration of limestone wall rocks also occurred at this stage. Elsewhere in the region, similar faults contain economic quantities of galena and elemental sulphur mineralization. Comparisons between the Pb and S isotope compositions of minerals found in cave and ore deposits confirm the link between economic mineralization and hydrothermal activity at Cupp-Coutunn. The predominance of sulphate mineralization in Cupp-Coutunn implies that the fluids were more oxidized in the higher permeability zone associated with the karst aquifer. A slight increase in the ,34S of sulphate minerals and a corresponding ,34S decrease in sulphides suggest that partial isotopic equilibration occurred during oxidation. Carbonate minerals indicate that the hydrothermal fluid was enriched in 18O (,18OSMOW , + 10,) relative to meteoric groundwater and seawater. Estimated values for ,13CDIC (,13CPDB , , 13,) are consistent with compositions expected for dissolved inorganic carbon (DIC) derived from the products of thermal decomposition of organic matter and dissolution of marine carbonate. Values derived for ,13CDIC and ,18Owater indicate that the hydrothermal fluid was of basinal brine origin, generated by extensive water,rock interaction. Following the hydrothermal phase, speleothemic minerals were precipitated under vadose conditions. Speleothemic sulphates show a bimodal sulphur isotope distribution. One group has compositions similar to the hydrothermal sulphates, whilst the second group is characterized by higher ,34S values. This latter group may either record the effects of microbial sulphate reduction, or reflect the introduction of sulphate-rich groundwater generated by the dissolution of overlying evaporites. Oxygen isotope compositions show that calcite speleothems were precipitated from nonthermal groundwater of meteoric origin. Carbonate speleothems are relatively enriched in 13C compared to most cave deposits, but can be explained by normal speleothem-forming processes under thin, arid-zone soils dominated by C4 vegetation. However, the presence of sulphate speleothems, with isotopic compositions indicative of the oxidation of hydrothermal sulphide, implies that CO2 derived by reaction of limestone with sulphuric acid (,condensation corrosion') contributed to the formation of 13C-enriched speleothem deposits. [source] A block-on-ring tribocorrosion setup for combined electrochemical and friction testingLUBRICATION SCIENCE, Issue 3 2007M.S. Jellesen Abstract The combined action of corrosion and wear can cause degradation of equipment, and thereby financial losses related to the renewal or repair of damaged equipment. In the food industry, metal degradation is a major concern since metal release eventually can cause health risks for consumers. This study describes a block-on-ring testing facility used to determine sliding wear, and additionally allowing for electrochemical measurements, such as potentiodynamic polarization curves and potentiostatic monitoring of current and potential. To verify the reliability and reproducibility of this block-on-ring tribocorrosion setup, the tribological and electrochemical behaviour of stainless steel sliding against a ceramic ring in sulphuric acid has been determined. Furthermore, a case taken from the food industry has been examined. The study shows that results made on the described block-on-ring testing facility are reliable and can provide improved information about material properties when the material is exposed to combined chemical and mechanical degradation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Quantitative determination of phyllanthin and hypophyllanthin in Phyllanthus species by high-performance thin layer chromatographyPHYTOCHEMICAL ANALYSIS, Issue 6 2006Arvind K. Tripathi Abstract A simple, precise and rapid high-performance thin-layer chromatographic method has been developed for the estimation of phyllanthin (1) and hypophyllanthin (2), the important lignans of Phyllanthus species, especially Phyllanthus amarus. Separation of 1 and 2 was carried out on silica gel 60 F254 layers eluted with hexane:acetone:ethyl acetate (74:12:8), and the analytes were visualised through colour development with vanillin in concentrated sulphuric acid and ethanol. Scanning and quantification of spots was performed at 580 nm. Recoveries of 1 and 2 were 98.7 and 97.3%, respectively. The method was validated and the peak purities and limits of detection and quantification were determined. Copyright © 2006 John Wiley & Sons, Ltd. [source] Quantitative determination of oleane derivatives in Terminalia arjuna by high performance thin layer chromatographyPHYTOCHEMICAL ANALYSIS, Issue 4 2002D. V. Singh Abstract A simple, precise and rapid high performance thin layer chromatographic method has been developed for the simultaneous quantitative determination of five oleane derivatives, namely, arjunic acid, arjunolic acid, arjungenin, arjunetin and arjunglucoside I from stem bark extract of Terminalia arjuna. The isolation and separation of these compounds was carried out on 60F254 layers eluted with chloroform:methanol (90:10), and the analytes were visualised through colour development with vanillin in concentrated sulphuric acid:ethanol. Scanning and quantification of the spots at 640,nm showed good recoveries in the range 96.40,101.7%. Copyright © 2002 John Wiley & Sons, Ltd. [source] Citric acid traps to replace sulphuric acid in the ammonia diffusion of dilute water samples for 15N analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2006Patrick Schleppi The analysis of 15N in aqueous samples requires the concentration of dissolved nitrogen (N) into a small volume that can be analysed by mass spectrometry. This is conveniently achieved by the NH3 diffusion technique, where NH is captured on small acidified filters enclosed in PTFE. NO can be analysed the same way by reducing it to NH with Devarda's alloy. H2SO4 is commonly used for the acidification of the filters. During combustion, however, this acid leads to the production of SO2 and elemental sulphur, which both have detrimental effects on the mass spectrometer. We propose here to replace H2SO4 with citric acid because it is combusted completely to CO2 and H2O in the elemental analyser before entering the mass spectrometer. Citric acid was found to give comparable results in terms of N recovery and 15N values, both for NH and for NO samples. Blank samples revealed that N contamination was slightly lower using citric instead of sulphuric acid as acidifier of the glass filters. NH samples first concentrated over cation-exchange columns were strongly acidic and several methods were tested to raise the pH for the subsequent diffusion. These samples gave incomplete N recoveries, but this problem was independent of the acid used on the filters and of the final pH of the sample. Complete recovery was achieved only by increasing the volume of the eluate from the columns. Citric acid can thus generally be recommended instead of H2SO4 for ammonia diffusion. Copyright © 2006 John Wiley & Sons, Ltd. [source] Chemical injuries: The Tasmanian burns unit experienceANZ JOURNAL OF SURGERY, Issue 1-2 2003Sophie Ricketts Background: Chemical burns account for relatively few admissions to a burns unit. These injuries, however, deserve separate consideration because of their ability to cause continuing tissue destruction, their potential to cause systemic toxicity and the value of early treatment with copious lavage. Widespread inexperience in the treatment of chemical burns highlights the potential for greater levels of general awareness and knowledge. Methods: A review of 31 patients with chemical injuries admitted to the Tasmanian Burns Unit at the Royal Hobart Hospital (RHH) was carried out for the years 1989,1999. Results: The majority of patients were men aged 20,49 years (mean age: 32 years). Fifty-one per cent of injuries occurred in a domestic and 38% in an industrial setting. The more common aetiological agents were cement (25%), sulphuric acid (16%) and hydrofluoric acid (16%). The upper and lower extremities were involved in all but four patients and the mean total body surface area affected was 3.4%. The mean length of hospital stay was 9 days with a range of 1,30 days. Management of injuries consisted of either surgical or conservative treatment. The former included debridement and split-thickness skin grafting or primary closure and the latter of topical treatment with 1% silver sulfadiazine cream and appropriate dressings. Conclusion: Widespread inexperience in the treatment of chemical injuries highlights the potential for greater levels of knowledge. This is particularly apparent in the early management of these injuries. [source] Facile Synthesis and In-Vitro Antitumor Activity of Some Pyrazolo[3,4- b]pyridines and Pyrazolo[1,5- a]pyrimidines Linked to a Thiazolo[3,2- a]benzimidazole MoietyARCHIV DER PHARMAZIE, Issue 1 2010Hatem A. Abdel-Aziz Abstract The key precursor E -3-(N,N -dimethylamino)-1-(3-methylthiazolo[3,2- a]benzimidazol-2-yl)prop-2-en-1-one 4 was synthesized in good yield using Gold's reagent. The reaction of enaminone 4 with 5-amino-3-aryl-1 - phenylpyrazoles 5a, b in refluxing acetic acid in the presence of sulphuric acid, yielded pyrazolo[3,4- b]pyridines 7a, b. Similarly, pyrazolo[1,5- a]pyrimidines 10a, b and 14a,f were prepared by reaction of enaminone 4 with 5-amino-1H -pyrazoles 8a, b and 12a,f, respectively. The structure of pyrazolo[1,5- a]pyrimidine 10b was determined by X-ray diffraction. The synthesized compounds were tested for their in-vitro antitumor activity against the colon cancer cell line CaCo-2; their cytotoxicity against the normal fibroblast cell line BHK was explored as well. Some of the tested compounds exhibited cell growth inhibitory activity. The significant antitumor activity of compound 14f against the CaCo-2 cell line (IC50 = 0.5 ,g/mL) was coupled with a lower toxicity against BHK (IC50 = 2.3 ,g/mL). [source] Epoxidation of Jatropha (Jatropha curcas) oil by peroxyacidsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010Vaibhav V. Goud Abstract Jatropha (Jatropha curcas) oil with iodine value 104 g I2/100 g, and containing 44.7% oleic acid and 31.4% linoleic acid, was epoxidised in situ with hydrogen peroxide (30%) and acetic/formic acid in the presence of catalytic amounts of sulphuric acid. We have compared the kinetics of epoxidation of jatropha oil (JO) by peroxyacetic and peroxyformic acids, in or without toluene at 30, 50, 70, and 85 °C. The effects of temperature and various mole ratios on epoxidation rate, oxirane ring stability, and iodine value of the epoxidised oil were studied, and optimum conditions were established. The rate constants for epoxidation of JO were found to be in the range 0.22,69.4 × 10,6 l.mol,1.s,1 and activation energies were found to be 64.46 KJ.mol,1, 72 KJ.mol,1, 59 KJ.mol,1, 68.24 KJ.mol,1, for peroxyacetic and peroxyformic acids in or without toluene, respectively. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | |||||||||||||