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Activation energies for the thermal decomposition reactions of hydrates and basic salts of FeSO4 were calculated using both conventional and statistical methods. The advantage and disadvantage of both methods is brought out. A combined method is proposed.

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The kinetics of thermal decomposition of iron(II) sulphate hexa- to monohydrates, as well as the hydroxy- and oxysulphates of iron(III), are presented and discussed. The results confirm that the final intermediate that decomposes to iron(III) oxide and sulphur trioxide during the thermal decomposition of any hydrate of iron(II) sulphate is the oxysulphate, Fe2O(SO4)2.

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Series of basic sulphates which were precipitated by the hydrolysis of Fe(OH)SO4 in the presence and absence of metallic iron were studied from compositional, crystallographic and thermal decomposition points of view. The results are presented and discussed. It was found that high pure iron oxides as well as high grade red iron oxide pigments can be obtained by agitating the basic sulphates in hot ammonical medium followed by roasting. Commercial exploitation of the results is suggested.

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Thermal analysis of iron(II) sulphate heptahydrate in air

III. Thermal decomposition of intermediate hydrates

Journal of Thermal Analysis and Calorimetry
Authors: M. S. R. Swami and T. P. Prasad

Iron(II) sulphate hydrates (hexa- through mono-) have been prepared and their thermal decomposition behaviours have been studied in air by isothermal and dynamic thermal analysis methods. The results show that their behaviours are similar to that of the heptahydrate. The stepwise loss of water molecules is accompanied by oxidation. Under a restricted supply of oxygen, the anhydrous sulphate is oxidized directly to Fe2O(SO4)2 without the formation of Fe(OH)SO4. When free exchange with oxygen is allowed, Fe(OH)SO4 is formed, which in turn decomposes to Fe2O(SO4)2. The decomposition of Fe2(SO4)2 to iron(III) oxide and sulphur oxides appears to occur via two independent paths — one direct and other through iron(III) sulphate.

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Iron(II) sulphate heptahydrate undergoes decomposition in the presence of basic beryllium carbonate without any interaction with the carbonate. The components of the mixture decompose individually. Iron(II) sulphate decomposes with the formation of tetrahydrate, monohydrate, anhydrous salt, oxysulphate and ferric sulphate as intermediate phases. The basic beryllium carbonate decomposes to the oxide with BeO·BeCO3 as the intermediate compound.

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The thermal decomposition of iron(II) sulphate heptahydrate was carried out in air under dynamic conditions in the presence of lithium, sodium, potassium and rubidium carbonates. The decomposition path in the presence of lithium carbonate differs from that in the presence of the other carbonates. In the presence of lithium carbonate, the heptahydrate loses all the water molecules before entering into reaction with the carbonate. The anhydrous sulphate then reacts with the carbonate, presumably to form iron(II) carbonate, which in turn undergoes decomposition — oxidation via magnetic oxide to ferric oxide. In the case of the other carbonates, iron(II) sulphate enters into reaction with the carbonate in question even before dehydration is complete, to form ferrous carbonate, which in turn reacts with the moisture still present to form green iron(II) hydroxide. This compound then undergoes decomposition — oxidation reactions via magnetic oxide to ferric oxide.

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Abstract  

Nuclear analytical techniques namely fission track technique using solid state nuclear track detector (SSNTD) and instrumental neutron activation analysis (INAA) have been standardized and applied for quantification of low uranium concentrations in liquid samples such as feed, elute and brine and solid sorbent samples respectively. The quantification of uranium is required for its recovery study from seawater, which is one of the potential sources of uranium. The uranium concentration of a liquid sample obtained by SSNTD method was compared with the other well established conventional techniques like ICP-MS, ICP-AES, adsorptive stripping voltametry and alpha spectrometry. INAA was applied for uranium concentration determination in the radiation grafted polyamidoxime sorbent samples.

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Abstract  

Soil samples collected at the Indian Antarctic station Maitree, situated at the Schirmachar Oasis and belonging to the East Antarctic charnockite provinces have been analysed to determine trace uranium concentrations. The fission track technique using Makrofol-KG as the track detector was used for the analyses. Finely powdered samples and pellets were irradiated with thermal neutrons from a nuclear reactor. Uranium concentrations were obtained from the tracks of the detector. Uranium concentrations were found to vary from 0.036 to 0.364 ppm in the samples investigated. The low levels of uranium indicate the absence of human intervention with the lithosphere in this region.

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Thermal analysis of ferrous sulphate heptahydrate in air

II. The oxidation-decomposition path

Journal of Thermal Analysis and Calorimetry
Authors: M. S. R. Swamy, T. P. Prasad, and B. R. Sant

The thermal decomposition of ferrous sulphate heptahydrate was carried out in air under dynamic and isothermal conditions. The intermediate phases were identified by chemical analysis and an X-ray technique. Ferrous sulphate heptahydrate is converted to tetrahydrate and monohydrate, but this conversion is accompanied by oxidation. Fe(OH)SO4 and Fe2O(SO4)2 are formed as oxidation products, and the latter decomposes to ferric oxide directly and/or through Fe2(SO4)3.

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Thermal analysis of ferrous sulphate heptahydrate in air

Part I. Some general remarks and methods

Journal of Thermal Analysis and Calorimetry
Authors: M. S. R. Swamy, T. P. Prasad, and B. R. Sant

The literature on thermal analysis of ferrous sulphate heptahydrate in air is reviewed. The oxidation-decomposition of ferrous sulphate heptahydrate is a complex function of experimental conditions. Some general methods including those developed by the authors for the purpose of analyzing various intermediates encountered during the oxidation-decomposition of the heptahydrate are presented and discussed.

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