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  • 1
    Electronic Resource
    Electronic Resource
    Gel filtration analysis of vanadium in Ascidia nigra blood cell lysate (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 93 (1977), S. 309-311 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Fractions from a Sephadex gel filtration of homogenized Ascidia nigra blood cell lysate were analyzed for vanadium by atomic absorption spectroscopy. The results were unaffected by temperature from 4-21°C, and by ionic strength in the range 0.09-1.0 M (NaCl). Appreciable loss of vanadium in the supernatant was experienced above pH 2.2. Experiments at pH 2.1 under anaerobic conditions show that the green chromogen and the vanadium-containing bands elute separately. Under these experimental conditions, the vanadium-containing species is of relatively low (⋍ 1,000) molecular weight.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040930217
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  • 2
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of the oxidation of thiourea by chlorine dioxide (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 25 (1993), S. 53-62 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stoichiometry and kinetics of the oxidation of thiourea (SC(NH2)2) by chlorine dioxide (ClO2) have been studied by uv-vis spectrophotometry using conventional and stopped-flow mixing techniques at 25.0 ± 0.1°C, pH 0.3-4.8. In high acid and initial 10:1 molar ratio of thiourea to chlorine dioxide, thiourea is oxidized relatively rapidly to dithiobisformamidine ion ((NH2)2CSSC(NH2)22+), which slowly decomposes to thiourea, sulfur, and cyanamide (NCNH2). In high acid and excess ClO2, thiourea is oxidized to relatively stable formamidine sulfinic acid ((NH) (NH2)CSO2H). In high acid and molar ratios of ClO2 to thiourea of 5:1 and higher, some oxidation to formamidine sulfonic acid ((NH) (NH2)CSO3H) occurs. At lower acidity, along with Cl-, the major ClO2 reduction product, byproduct sulfate is detected and, at pH 〈 3, ClO2-, also, appears. Kinetics data were collected for high excess thiourea with varying pH. The [ClO2]-time curves are straight lines with negative slopes that increase in magnitude with increasing [thiourea]. The dependence on [thiourea] is first-order; the dependence on [ClO2] is zero-order for 90% of reaction. With decreasing pH, the rate increases and the disappearance of ClO2 becomes autocatalytic. Studies of the effects of reaction products on the rate of reaction lead to the conclusion that autocatalysis at low pH is due to the greater reactivity of HClO2 compared with ClO2-. A 10-step mechanism incorporating a slow one-electron transfer from thiourea to ClO2 to generate the (NH) (NH2)CS · radical and subsequent more rapid reactions has been constructed and implemented in a computer simulation which provides a reasonably accurate fit to the observed kinetics curves. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550250106
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  • 3
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of the reaction between thiosulfate and chlorite ions at 90°CSystematic Design of Chemical Oscillators. Part 32. Part 31: M. Alamgir and I.R. Epstein, J. Phys. Chem., 89, 3611 (1985) (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 18 (1986), S. 345-353 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the oxidation of S2O32- by ClO2- have been studied in aqueous alkaline solution at 900C using classical titrimetric methods to follow the course of the reaction. The reaction takes place according to the stoichiometry S2O32- + 2ClO2- + 2OH- = 2SO42- + 2Cl- + H2O even in large S2O32- excess. There is some indication of a complex reaction pattern, but 70% of the ClO2- disappearance can be best described by the autocatalytic rate equation -d[ClO2-]/dt = k[S2O32-] [ClO2-] [H+] with k = (1.3 ± 0.2) ×108 M-2 sec-1. The mechanism is explained by postulating nucleophilic attack of S2O32- on HClO2 to form a chlorine-containing intermediate.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550180307
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  • 4
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of the iodine oxidation of hydroxylamine (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 24 (1992), S. 11-18 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies of the stoichiometry and kinetics of the reaction between hydroxylamine and iodine, previously studied in media below pH 3, have been extended to pH 5.5. The stoichiometry over the pH range 3.4-5.5 is 2NH2OH + 2I2 = N2O + 4I- + H2O + 4H+. Since the reaction is first-order in [I2] + [I3-], the specific rate law, k0, is k0 = (k1 + k2/[H+]) {[NH3OH+]0/(1 + Kp[H+])} {1/(1 + KI[I-])}, where [NH3OH+]0 is total initial hydroxylamine concentration, and k1, k2, Kp, and KI are (6.5 ± 0.6) × 105 M-1 s-1, (5.0 ± 0.5) s-1, 1 × 106 M-1, and 725 M-1, respectively. A mechanism taking into account unprotonated hydroxylamine (NH2OH) and molecular iodine (I2) as reactive species, with intermediates NH2OI2-, HNO, NH2O, and I2-, is proposed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550240103
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of pyrogallol autoxidation: Calibration of the dynamic response of an oxygen electrodePart 63 in the series Systematic Design of Chemical Oscillators. Part 62: M. Orbán and I.R. Epstein, J. Am. Chem. Soc., 112, 1812 (1990). (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 25 (1993), S. 239-247 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the reaction between 1,2,3-trihydroxybenzene (pyrogallol) and O2 (autoxidation) have been determined by monitoring the concentration of dissolved dioxygen with a polarographic oxygen electrode. The reaction is carried out in pseudo-first-order excess pyrogallol, 25°C, 0.08 M NaCl, and 0.04 M phosphate buffer in the pH range 6.9-10.5. Data collection precedes reaction initiation, but only the data recorded after the estimated 3.2 s dead time are used in kinetics calculations. Observed rate constants are corrected for incomplete mixing, which is treated as a first-order process that has an experimentally determined mixing rate constant of 4.0 s-1. The rate law for the reaction is -d[O2]/dt=kapp[PYR]tot[O2], in which [PYR]tot is the total stoichiometric pyrogallol concentration. A mechanism is presented which explains the increase in rate with increasing [OH-] by postulating that H2PYR- (k2) has greater reactivity with dissolved dioxygen than does H3PYR (k1). The data best fit the equation kapp=(k1 + k2KH[OH-])/(1 + KH[OH-]) when the value of the hydrolysis constant KH (the quotient of the pyrogallol acid dissociation and water autoprotolysis constants) for this medium equals 3.1×104 M-1. The resulting values of k1 and k2, respectively, equal (0.13 + 0.01) M-1 s-1 and (3.5 plusmn; 0.1) M-1 s-1. This reaction is recommended as a test reaction for calibrating the dynamic response of an O2-electrode. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550250404
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