Journal ArticleDOI

The thermal decomposition of potassium bromate in the presence of chromium(III) oxide

01 Aug 1976-Thermochimica Acta (Elsevier)-Vol. 242, Iss: 2, pp 215-221

TL;DR: In this article, thermal decomposition studies of intimate mixtures of different molar ratios of potassium nitrate and chromium(III) oxide were made by employing thermogravimetry differential thermal analysis, chemical analysis, infrared spectral measurements and X-ray powder diffraction patterns.

AbstractThermal decomposition studies of intimate mixtures of different molar ratios of potassium nitrate and chromium(III) oxide were made by employing thermogravimetry differential thermal analysis, chemical analysis, infrared spectral measurements and X-ray powder diffraction patterns. Potassium nitrate in the presence of chromium(III) oxide starts decomposing around 350°C which is much below the decomposition temperature of pure potassium nitrate. Chromium(III) is completely oxidized into its hexavalent state when the mole ratio of KNO3 to Cr2O3 is greater than three.

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Citations
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Journal ArticleDOI
TL;DR: In this article, structural defects were introduced into the potassium bromate (PB) lattice in the form of SO2− 4 and Cl− ions in the process of crystal growth.
Abstract: Structural defects were introduced into the potassium bromate (PB) lattice in the form of SO2− 4 and Cl− ions in the process of crystal growth. It was assumed that these doped crystals PB(Cl−) and PB(SO2− 4) are composed of a two phase system, one being the perfect PB lattice and the other distorted regions due to induced defects. Isothermal decomposition of doped and normal PB samples was carried out gasometrically between the temperature range 653–663 K. The α-t plots reveal that the process occurs through initial gas evolution, acceleratory and decay stages. It also confirmed that doping enhances the rate of the reaction, the effect being more pronounced in the case of PB(SO2− 4). The data are found to be well fitted to the Prout-Tompkins and Avrami-Erofe'ev mechanisms.

10 citations

Journal ArticleDOI
TL;DR: In this paper, the kinetic and activation energies of thermal decomposition of KNO3 as an oxidizer in pyrotechnic compositions were studied in the presence of Fe2O3 nanoparticles as catalysts, using thermogravimetric analysis under argon atmosphere at different heating rates (10, 15, and 20 Kmin−1).
Abstract: The kinetic and activation energies of thermal decomposition of KNO3 as an oxidizer in pyrotechnic compositions were studied in the presence of Fe2O3, Mn2O3, and TiO2 nanoparticles as catalysts, using thermogravimetric analysis under argon atmosphere at different heating rates (10, 15, and 20 K min−1). The prepared nanoparticles were characterized by XRD patterns, SEM images, and BET surface area analysis. For verification of data, the activation energies for thermal decomposition of KNO3 were calculated using non-isothermal isoconversional methods of KAS, OFW, and Friedman for different conversion fraction (α) values in the range 0.1–0.9. The activation energies were 201.6–208.2, 170.0–177.9, 173.9–181.6, and 213.0–223.8 kJ mol−1, respectively, in the absence and presence of 5 mol% of Fe2O3, Mn2O3, and TiO2. The results indicated that while Fe2O3 and Mn2O3 nanoparticles have catalytic effects, TiO2 nanoparticles show inhibitory effect on the thermal decomposition of KNO3.

9 citations

Journal ArticleDOI
TL;DR: The large scale manufacture of sodium chromate is carried out by heating finely ground chromite ore mixed with sodium carbonate and lime in air as discussed by the authors, and the essential reaction leading to the formation of the sodium chromates is the reaction of the mixture of chromite and lime.
Abstract: The large scale manufacture of sodium chromate is carried out by heating finely ground chromite ore mixed with sodium carbonate and lime in air. The essential reaction leading to the formation of sodium chromate is $$2Cr_2 O_3 + 4 Na_2 CO_3 + 3 O_2 \xrightarrow{{\Delta {\rm H}_{R^0 } }}4Na_2 CrO_4 + CO_2$$

5 citations

Journal ArticleDOI
A. K. Tripathy
TL;DR: In this article, low temperature isothermal kinetic studies were performed on alkali roasting of Cr2O3 with progressive replacement of Na2CO3 in the reaction mixture by NaNO3 in a temperature range of 573 to 873 K. The influence of the nitrate on the course of the reactions was studied.
Abstract: Low temperature isothermal kinetic studies were performed on alkali roasting of Cr2O3 with progressive replacement of Na2CO3 in the reaction mixture by NaNO3 in the temperature range of 573 to 873 K. The influence of the nitrate on the course of the reactions was studied. Statistical design of experiments was employed to asses the relative influence of different process variables. Kinetic analysis of the experimental data shows that the reaction with NaNO3 follows a simple first-order model, and the activation energy of the reaction is 22.7 kJmol-1, as compared to 72 kJmol−1 for Na2CO3 flux.

4 citations

Journal ArticleDOI
TL;DR: In this paper, a powder x-ray diffraction (PXRD) method for detecting KBrO3 adulteration in bakery ingredients and products was proposed and validated using ICCD and COD databases.
Abstract: Potassium bromate is used in the baking industry as a bread improver and is known to improve dough kneading characteristics and bread volume. However, over the years, its carcinogenic nature has been established and KBrO3 is considered a hazardous adulterant in food systems. This study aimed to develop and validate a novel powder x-ray diffraction (PXRD) method for the detection of KBrO3 adulteration in bakery ingredients and products. Different combinations of x-ray tube voltage (25–45 kV), tube current (25–45 mA), step size (0.006°–0.13°), and time per step (50–150 s) were experimented on an angle of 15°–90° at 25 °C with CuKα radiation (λ = 1.5418 A). The KBrO3 phase was identified based on the peak values of 2θ and Miller indicate (hkl) and was confirmed using ICCD and COD crystallography databases. Based on the observation, x-ray tube voltage (45 kV), current (45 mA), step size (0.006 A), and net time per step (150.450 s) were found to be the optimal diffraction conditions for the detection of KBrO3. This study demonstrates the potential of XRD as a non-destructive, rapid, and reliable method for the detection of KBrO3 in bakery products.

4 citations

References
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TL;DR: The No. 10123 1quart "Success" can as discussed by the authors dispenses solvent by finger pressure on the valve, which then closes upon release of the pressure, as indicated in the accompanying figure.
Abstract: use and allows it to dispense no more solvent than is needed when the swab-stick is dipped into it like a pen into an inkwell. Available in 4 oz., 6 oz., and 8 oz. sizes, the price ranges from $3. 50 to$3. 75. This same company also advertises a model No. 10123 1quart "Success" can which dispenses solvent by finger pressure on the valve, which then closes upon release of the pressure, as indicated in the accompanying figure. There is also a plunger can of I-pint size that dispenses solvent by pressure on the plunger. Price for the first type of can is about $8, for the second, about$7.

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TL;DR: In this article, the characteristic frequencies of 52 metals have been studied in the region 700-240 cm−1 and a particle size of 10 μ or smaller was found to give the best representative spectrum.
Abstract: The characteristic frequencies of oxides of 52 metals have been studied in the region 700-240 cm−1. Data for oxides of metals of different valence states and the frequencies of polymorphic forms of several oxides are presented. A particle size of 10 μ or smaller was found to give the best representative spectrum.

474 citations

Journal ArticleDOI
TL;DR: In this article, the infrared spectra from 300-880 cm−1 of 208 inorganic substances are reported, nearly all of which are salts containing polyatomic ions, and a list of characteristic frequencies is given for twenty ions.
Abstract: The infrared spectra from 300–880 cm−1 of 208 inorganic substances are reported. Nearly all are salts containing polyatomic ions. Spectral curves are presented for 140 of the compounds, and a list of characteristic frequencies is given for twenty ions. Among other matters discussed are: (a) the non-reproducibility of some of the spectra, and reasons for this, (b) absorption due to the torsional oscillation of water molecules, and (c) some vibrational assignments for MnO4−1 and CrO42−1.

188 citations

Journal ArticleDOI

134 citations

Journal ArticleDOI
TL;DR: In this paper, a study of the thermal decomposition of intimate mixtures of different molar ratios of KClO4 and chromium(III) oxide was conducted employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis.
Abstract: A study of the thermal decomposition of intimate mixtures of different molar ratios of potassium perchlorate and chromium(III) oxide, and potassium perchlorate and nickel(II) chromite(III) was conducted employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis. Upon heating to 400°C Cr(III), in 2:1 molar ratios, is oxidized to potassium dichromate. Only a stoichiometric amount of Cr(III) was oxidized from molar ratios less than 2:1, leaving behind excess Cr2O3 and NiCr2O4 whereas from molar ratios greater than 2:1, Cr(III) was completely oxidized and the excess KClO4 started decomposing around 410°C which is much below the decomposition temperature of pure KClO4.

22 citations