Thermal analysis of iron(II) sulphate heptahydrate in air

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.     

Thermal analysis of iron(II) sulphate heptahydrate in air. V

The thermal decomposition of the hydroxysulphate and oxysulphate of iron(III) was carried out in air. Under dynamic conditions, the hydroxysulphate decomposes to the oxysulphate, which in turn decomposes to iron(III) oxide and sulphur oxides. The oxysulphate decomposes directly to iron(III) oxide and sulphur oxides. The heats of decomposition and heats of formation of the two basic sulphates were calculated.     

Thermal decomposition of iron(II) sulphate heptahydrate in air in the presence of basic magnesium carbonate

Results on the thermal decomposition of iron(II) sulphate heptahydrate in the presence of basic magnesium carbonate are presented and discussed. These results are compared with those for the mixture of iron(II) sulphate heptahydrate with basic beryllium carbonate. While no reaction occurs between the components in the case of basic beryllium carbonate, basic magnesium carbonate reacts readily with iron(II) sulphate heptahydrate.

---

Zusammenfassung Bei der in Gegenwart von basischem Magnesiumcarbonat erfolgten thermischen Zersetzung von Eisen(II)-sulfat-Heptahydrat erhaltene Ergebnisse werden beschrieben, diskutiert und mit denen verglichen, die in Gegenwart von Berylliumcarbonat erhalten wurden. Im Gegensatz zu basischem Berylliumcarbonat reagiert basisches Magnesiumcarbonat mit Eisen(II) sulfat-Heptahydrat.

---

. . , , .

---

---

The author gratefully acknowledges the support extended by Professor P. K. Jena, Director of this laboratory, and the permission to publish the results.     

Thermal decomposition of iron(II) sulphate heptahydrate in air in the presence of (basic) beryllium carbonate

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.

---

Zusammenfassung In Gegenwart von basischem Berylliumcarbonat zersetzt sich Eisen(II)-sulfat-Heptahydrat, ohne mit dem Carbonat in Wechselwirkung zu treten. Die Komponenten des Gemisches zersetzen sich individuell. Die Zersetzung des Eisen(II)-sulfats verläuft über die Zwischenphasen Tetrahydrat, Monohydrat, wasserfreies Salz, Oxysulfat und Eisen(III)-sulfat. Das basische Berylliumcarbonat wird über die intermediäre Verbindung BeO·BeCO₃ in das Oxid überführt.

---

, . . , , , . .₃.

---

---

The authors are grateful to Dr. B. R. Sant for his keen interest and useful suggestions throughout this work. They also express their sincere thanks to Prof. P. K. Jena, Director, for his kind permission to publish the results. One of us (MSRS) thanks the Director for a Senior Fellowship.     

Thermal decomposition of iron(II) sulphate heptahydrate in air in the presence of calcium,strontium and barium carbonates

The thermal decomposition in air of iron(II) sulphate heptahydrate in the presence of calcium, strontium and barium carbonates has been carried out. The decomposition path varies from carbonate to carbonate. Also, these decompositions are different from those of basic beryllium carbonate and basic magnesium carbonate. The results obtained for the kinetics of thermal decomposition have also been presented.     

Thermal decomposition of iron(II) sulphate heptahydrate in the presence of alkali metal carbonates

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.

---

Zusammenfassung Die thermische Zersetzung von Eisen(II)-sulfat-Heptahydrat wurde in Luft unter dynamischen Bedingungen in Gegenwart von Lithium-, Natrium-, Kalium und Rubidiumcarbonat ausgeführt. In Gegenwart von Lithiumcarbonat verläuft die Zersetzung auf einem anderen Wege als in Gegenwart der anderen untersuchten Carbonate. In Gegenwart von Lithiumcarbonat verliert das Heptahydrat alle Wassermoleküle, bevor es mit dem Carbonat in Reaktion tritt. Das wasserfreie Sulfat reagiert mit dem Carbonat vermutlich unter Bildung von Eisen(II)-carbonat, das oxydativ über Magnetit zu Eisen(III)-oxid zersetzt wird. Im Falle der anderen Carbonate tritt Eisen(II)-sulfat mit dem betreffenden Carbonat noch vor der völligen Beendigung der Dehydratation unter Bildung von Eisen(II)-carbonat in Reaktion, das daraufhin mit noch vorhandenem Wasser zu grünem Eisen(II)-hydroxid weiterreagiert. Diese Verbindung zersetzt sich oxydativ über Magnetit zu Eisen(III)-oxid

---

, , . . . , , - . , , . .

---

---

The authors express their sincere thanks to Dr. B. R. Sant for his keen interest in this work and for his valuable suggestions. They also express their gratitude to Professor P. K. Jena, Director, for his permission to publish the results. One of us (MSRS) also thanks the Director for a Senior Fellowship.     

Preparation and characterisation of magnesium sulphate heptahydrate from Kimberlite tailings

Weathered Kimberlite tailings of Panna Diamond Mines were characterised by DTA and XRD techniques. The XRD pattern shows the presence of serpentine, quartz, calcite, hematite, magnetite and anatase phases. DTA curve indicates first endothermic peak at 125C due to dehydration of the mineral and second endo peak at 670C due to dehydroxylation of serpentine closely followed by an exothermic peak at 810C associated with the formation of forsterite. XRD and DTA studies of sulphuric acid leach residue of the Kimberlite shows the disappearance of serpentine phase with the appearance of CaSO₄·2H₂O phase. The product MgSO₄·7H₂O obtained after purification and crystallisation. From the optical emission spectroscopic analysis, the product was found to contain Ca, Fe and SiO₂ as trace impurities.

---

Zusammenfassung Mittels DTA und Röntgendiffraktion wurden verwitterte Kimberlit-AbgÄnge aus Diamantbergwerken in Panna charakterisiert. Das Röntgendiagramm zeigt die Gegenwart von Serpentin-, Quarz-, Kalzit-, HÄmatit-, Magnetit- und Anatas-Phasen. Die DTA-Kurve zeigt einen ersten endothermen Peak bei 125C (Dehydratation des Minerales) und einen zweiten endothermen Peak bei 670C (Dehydroxylierung von Serpentin), eng gefolgt von einem exothermen Peak bei 810C (Bildung von Forsterit). Röntgendiffraktionsund DTA-Untersuchungen an einem schwefelsauren Extraktionsauszug von Kimberlit zeigen das Verschwinden der Serpentin-Phase, aber das zusÄtzliche Auftreten einer CaSO₄·2H₂O-Phase. Nach Reinigung und Kristallisation wurde MgSO₄·7H₂O als Produkt erhalten, dessen optische emissionsspektroskopische Untersuchung in Spuren Verunreinigungen mit Ca, Fe und SiO₂ zeigten.

     

Thermal decomposition of iron(II) sulphate in air. IV

Heats of decomposition and formation of various hydrates of iron(II) sulphate have been presented and discussed. The heat of dehydration of the monohydrate calculated from the DTA curves (50.2 kJ/mole) appears to be lower than the expected value. The value calculated from the heats of formation (79.4 kJ/mole) is therefore taken as the more accurate value.

---

Zusammenfassung Die Zersetzungs- und Bildungswärmen verschiedener Hydrate der Eisen(II)sulfate wurden aufgeführt und diskutiert. Die aus den DTA-Kurven berechnete Dehydratisierungswärme (50.2 kJ) des Monohydrats scheint niedriger zu sein als der erwartete Wert. Der aus den Bildungswärmen berechnete Wert (80.1) kJ) wird deshalb als der exaktere Wert angenommen.

---

Résumé On présente et discute les valeurs des chaleurs de décomposition et de formation de divers hydrates du sulfate de fer(II). La chaleur de déshydratation du monohydrate, calculée à partir des courbes d'ATD (50.2 kJ) paraît être plus faible que la valeur attendus. C'est pourquoi la valeur calculée à partir des chaleurs de formation (80.1 kJ) est considérée comme plus exacte.

---

(II). , , (50.2 ), . , , , 79.4 .

---

---

The authors express their grateful thanks to Dr. B. R. Sant for his keen interest and valuable suggestions, and to Prof. P. K. Jena, Director, for permitting the publication of the results. One of us (M. S. R. S.) is grateful to the RRL for the award of a Senior Research Fellowship.     

Potentiometric studies in oxidation-reduction reactions: Reduction with ferrous ethylenediamine sulphate ceric sulphate method

Ferrous ethylenediamine sulphate has been used as a reducing agent to determine indirectly potassium permanganate, ceric sulphate, potassium chlorate, hydrogen peroxide, potassium persulphate, potassium dichromate and potassium bromate by a potentiometric method. An excess of ferrous ethylenediamine sulphate added to each of the substances in acid medium was titrated with a standard solution of ceric sulphate, using platinum foil as an oxidation-reduction electrode coupled with a saturated calomel electrode through an agar-agar potassium chloride bridge.     

Volumetric studies in oxidation-reduction reactions: Reduction with ferrous ethylenediamine sulphate ceric sulphate method

Ferrous ethylenediamine sulphate has been used as a reducing agent in acid medium for the indirect volumetric estimations of potassium chlorate, potassium bromate, potassium metaperiodate, potassium dichromate, potassium ferricyanide, potassium permanganate, potassium persulphate, hydrogen peroxide and ceric sulphate. The excess of ferrous ethylenediamine sulphate added to each of the substances in acid medium was titrated with standard ceric sulphate solution using ferroin as an indicator.     

Mössbauer effect of ferrous zirconium double sulphate

The Mössbauer spectrum of ferrous zirconium double sulphate FeZrO(SO₄)₂·8H₂O shows a quadrupole split doublet at room temperature. The results are discussed in terms of high-spin Fe(II) in distorted octahedral symmetry.     

Dehydration of magnesium sulphate heptahydrate investigated by quasi isothermal—quasi isobaric TG

With the help of the quasi isothermal-quasi isobaric technique, completed with DTA and thermomicroscopic examinations, several new observations have been made regarding the dehydration process of MgSO₄ · 7 H₂O. It was found that under given conditions the material, first at 50°C and then at 95°C, melts in an incongruous way. In the course of the latter transformation, a ternary system consisting of solid MgSO₄ · 3 H₂O, a solution phase saturated with respect to the trihydrate, and a water vapour phase, is formed. The saturated solution reaches its boiling point at 105°C. Without any temperature change, the system loses four moles of water and solid MgSO₄ · 3 H₂O remains. This decomposes at 115°C and a mixture consisting of MgSO₄ · H₂O and MgSO₄ · 2 H₂O forms, the proportion of which depends on the experimental conditions. At 150°C, the latter compound loses one mole of water. The MgSO₄ · H₂O maintains constant weight up to 310°C, above which temperature the remaining water of crystallization is removed.     

Volumetric Studies In Oxidation-Reduction Reactions: Oxidation with ceric sulphate ferrous ethylenediamine sulphate method

Ceric sulphate has been used as an oxidizing agent in acid medium for the indirect volumetric determinations of ferrous ammonium sulphate, cuprous chloride, potassium thiocyanate, sodium thiosulpliate, sodiuin nitrite, hydrogen peroxide, sodium oxalate, hydroquinone and pyruvic acid. The excess of ceric sulphate added to each of the substances in acid medium was titrated with standard ferrous ethylenediamine sulphate solution using ferroin as an indicator.     

Mössbauer effect and thermal analysis investigation of a frozen aqueous solution of ferrous sulphate

Aqueous FeSO₄.7H₂O solutions of different concentrations were quickly frozen to liquid nitrogen temperature and the zero-velocity Mössbauer transmission and differential thermoanalytical (DTA) curves were measured simultaneously as the samples warmed up. On the DTA curves an exothermic peak could be observed at about ?60°C. Also changes in the Mössbauer parameters were found to take place at this temperature.     

Thermal degradation of amphetamine sulphate

The pyrolysis of amphetamine sulphate was studied in a laboratory flow reactor in the range 350–1000°C. The identifications and quantitative determinations of most gaseous and condensed products by means of gas chromatography and mass spectrometry made possible the suggestion of a thermal degradation scheme. The presence of sulphate in the initial molecule led to oxidation reactions in addition to the usual thermal reactions that occur during the pyrolysis of organic materials.     

Kinetics of thermal decomposition of intermediate hydrates and basic salts of iron(II) sulphate heptahydrate

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.

---

Zusammenfassung Die Kinetik der thermischen Zersetzung von Eisen(II)-sulfat-Hexahydrat zum Monohydrat und von Hydroxy- und Oxysulfaten von Eisen(III) ist angegeben und wird diskutiert. Die Ergebnisse bestätigen, daß das letzte, sich zu Eisen(III)-oxid und Schwefeltrioxid zersetzende Zwischenprodukt bei der thermischen Zersetzung aller Hydrate von Eisen(II)-sulfat das Oxysulfat Fe₂O(SO₄)₂ ist.

---

( - ) , . , - Fe₂O(SO₄)₂, .

---

---

The author is grateful to Prof. P. K. Jena, Director, for his kind permission to publish the results.     

Thermal desorption-capillary gas chromatography for the quantitative analysis of dimethyl sulphate, diethyl sulphate and ethylene oxide in the workplace

Sampling on solid adsorbents followed by thermal desorption and gas chromatography was evaluated as a simple method for the quantitative analysis of dimethyl sulphate, diethyl sulphate and ethylene oxide in the workplace environment. Tenax TA and Carbosieve S-III (for ethylene oxide) were found to be suitable adsorbents. The charged tubes can be stored at 22 degrees C for 4 days. The recovery is better than 98% (greater than 80% for ethylene oxide) in the mass range 1 ng-1 micrograms. The recovery is not dependent on air humidity. The limits of detection tested were at the lower parts per billion level.     

Potentiometric studies in oxidation-reduction reactions: Reduction with ferrous ethylenediamine sulphate indirect determinations

Ferrous ethylenediamine sulphate has been used as a reducing agent to determine indirectly potassium dichromate, hydrogen peroxide, potassium permanganate, potassium persulphate, potassium chlorate, potassium bromate, and ceric sulphate by a potentiometric method. An excess of ferrous ethylenediamine sulphate added to each of the substances in an acid medium is titrated with a standard solution of potassium permanganate, using platinum foil as an oxidation-reduction electrode coupled with a saturated calomel electrode through an agar-agar potassium chloride bridge.     

Thermal decomposition of calcium sulphate in carbon monoxide

Simultaneous TG and DTA studies were performed on analytical grade calcium sulfate and on samples of natural gypsum and phosphogypsum in carbon monoxide atmosphere. The decomposition temperatures and mechanism are influenced by the mineral impurities of the sample and the heating rate as well as the CO content of the gas atmosphere.

---

Zusammenfassung Simultane TG- und DTA-Untersuchungen von analytisch reinem Calciumsulfat und Proben von natürlichem Gips und Phosphogips wurden in Kohlenmonoxidatmosphäre ausgeführt. Temperatur und Mechanismus der Zersetzung werden durch mineralische Verunreinigungen der Probe, durch die Aufheizgeschwindigkeit und durch den CO-Gehalt der Gasatmosphäre beeinflußt.

---

. - , , .

---

---

The authors are indebted to Professor M. Veiderma for fruitful discussions and continuous support. The scholarship from Finnish Government to one of us (R. K.) is gratefully acknowledged.