Ferrous Oxalate Research Articles

A Method for Bonding to Dentin and Enamel

In vitro tensile bond strengths of about 1 ton per square inch between composites and dentin and enamel were obtained by applying a 5.3% solution of ferric oxalate to the tooth surface, followed by water and air cleaning; by applying a 10% solution of NTG-GMA, followed by cleansing with solvent and air; by applying a 5% solution of PMDM, followed by air to remove the solvent; and by placing the freshly mixed composite against the treated surface. If this breakthrough in the laboratory leads to sufficiently durable adhesion in clinical practice, the conservation of retention-form dentin could increase patient comfort, reduce treatment time and cost, and lessen fatigue for dentists.

Sintering of Fine Iron Powders Produced from Ferrous Oxalate Dihydrate

The oxalate rather than the nitrate was chosen because of the difficulties in heating the latter and removing the large amounts of nitrogen oxides that would be formed. Many industrial processes, such as the Hogana.s process (magnetite and carbon) and the Pyron process (millscale and hydrogen), involve the decomposition of oxides to produce iron powders. Other techniques involve the chloride, as in the Peace River process,! to produce iron. The ammonium sulphates have been used to produce nickel powders as in the Sherrit-Gordon process.2 The last two processes involve heating the compound in a stream of hydrogen. The Sol-Gel process3 makes use of the hydroxide gels which are reduced in hydrogen; this method is able to produce submicrometre sized powders. More elaborate reduction processes are used by the Domsa process for making iron powders by the reduction of millscale (Fe304) in methane. Other methods using hydrides as reducing agents4 have been used to produce vanadium and chromium powders. Arias5 describes a method used to produce chromium and nickel from their oxides by reduction with magnesium, sodium, or lithium vapour. It is possible to use the carbony16 to produce nickel powders by heating alone, as in the Mond process, and in theory this process could be used to produce iron powders. In many of the processes mentioned it is sometimes difficult to control the final particle size of the powder and, in some iron powder production processes, a crushing/grinding/milling stage has to be introduced. The oxalate has not been used in an industrial metal powder production process so far; however, the present work was part of a larger research programme 7 investigating the kinetics of reduction processes involving metallic salts. The results on the fine iron powders produced from that research by this route are presented here because of

Thermal decomposition of ferrous oxalate dihydrate studied by direct current electrical conductivity measurements

The feasibility of the use of direct current electrical conductivity,σ, measurements in the study of solid-state reactions involved in the synthesis ofγ-Fe2O3 from ferrous oxalate dihydrate has been reported. The study has been carried out in static air, dynamic air, dry nitrogen and dynamic air + water vapour environments. The conductivity data determined in static air are quite complex; nevertheless, the formation of Fe3O4 andα-Fe2O3 with the probable intermediate formation ofγ-Fe2O3 has been indicated. In dry nitrogen the step corresponding to dehydration is well resolved in the temperature region 145–220° C; the formation of FeO and Fe3O4 is also well characterized. In dry dynamic air the reaction further proceeds to the formation ofα-Fe2O3. In dynamic air containing water vapour there are definite indications of the formation ofγ-Fe2O3 prior to the formation ofα-Fe2O3. Definite experimental conditions have been determined for the formation ofγ-Fe2O3 in dynamic air containing water vapour. The conductivity measurements have been supplemented with infra-red spectroscopy and X-ray diffraction pattern measurements. The electrical conductivity measurements were found to give additional information on the solid-state reaction to that obtained from conventional thermal analytical techniques (such as differential thermal, thermogravimetric and differential thermogravimetric analyses).γFe2O3, obtained from the decomposition of FeC2O4 · 2H2O in dynamic air + water was found to have a coercive force of 3.142 A m−1, a saturation magnetization value of 7.1 T kg−1 and a ratio of remanence to saturation magnetization of 0.64.

Preparation and characterisation of γ-Fe2O3 as tape recording material

Optimum conditions for the preparation of tape recording quality γ-Fe2O3 by the thermal decomposition of ferrous oxalate dihydrate have been established. Formation of the intermediate Fe3O4 which is most important in forming γ-Fe2O3 takes place only in the presence of water vapour. Various stages of decomposition have been characterised by DTA, TG, DTG, and x-ray powder diffraction. The method for the preparation of acicular γ-Fe2O3 that matches very well with the commercial tape recording material has been developed.

Synthesis and the thermal decomposition of iron(III) tris(oxalato) ferrate(III) tetrahydrate

The paper describes the synthesis and thermal decomposition of Fe[Fe(C 2O 4) 3]4H 2O in air. The compound is completely dehydrated at 170°C and some reduction in the inner sphere iron(III) occurs. At 290°C, a mixture of ferric oxide and ferrous oxalate is obtained. Beyond 420°C, the decomposition is complete and final residue is ferric oxide. A probable reaction mechanism is proposed.

IR and Mössbauer study of iron glycerolates

Iron glycerolates obtained from the reaction between Fe(II) and Fe(III) oxylates and glycerol were studied by means of X-ray diffraction, IR and Mössbauer spectroscopy. Regardless of the oxidation state of iron in the starting salt, the final glycerolates contain nearly identical Fe 2+/Fe 3+ ratios, but the crystallization from Fe(III) oxalate proceeds faster. As shown by Mössbauer spectroscopy, the first particles of glycerolate obtained from ferric oxalate contain only Fe 3+ species, whereas from ferrous oxalate, Fe 2+ and Fe 3+ are initially present in the glycerolate. Well crystallized glycerolate exhibits three Mössbauer doublets; two are due to Fe 2+ species in different environments and one to Fe 3+ species. Spectral features observed by IR spectroscopy are accounted for by the presence of both structural Fe 2+ and Fe 3+ species.

Dyeing Anodized Aluminium: A Review

SummaryThe theory and practice of dyeing anodized aluminium are briefly reviewed and discussed. The dyes used are anionic water soluble types similar to wool dyes. Adsorption is by ion exchange, the dye anion being attracted by the positive charge on the anodic alumina film, and adsorbed either as monodisperse anions or as anionic micelles. Some covalent bonding between dye and film may also occur. Inorganic salts with divalent or trivalent anions retard or prevent dyeing when present in the dyebath. After dyeing, the anodic film is sealed in boiling water. This treatment improves fastness to washing and light. For very high fastness some inorganic salts are used as dyes, for example, ferric ammonium oxalate for imitation gold and brass colours.

Synthèse à haute température d'un glycérolate de fer au départ d'oxalate ferreux et ferrique

Attempts at synthesizing high temperature crystalline organic complexes starting from glycerol and various iron salts have been achieved, particularly with ferrous and ferric oxalate. For these latter, the powdered reaction products at various stages of the synthesis were studied by X-ray diffraction, i.r. spectroscopy, electron microscopy and chemical analysis. At least two steps are involved in the formation of the glycerolate: (1) a rearrangement of the structure of the starting salt with formation of a sheet structure suitable for the glycerolate, and (2) a reduction or oxidation of metallic ions. Relative rates of these two steps depend on the structural stability of starting materials. Rapid decomposition of ferric oxalate produces the formation of a ferric-rich intermediate product: in this case, the limiting step of the reaction is the progressive reduction of the Fe 3+ ion. On the other hand, ferrous oxalate breaks up at a rather slow rate and the relative oxidation rate of Fe 2+ may become fast enough to favour the direct formation of the stable organic complex.

Square wave voltammetry at the dropping mercury electrode: experimental

Abstract : Experimental verification of earlier theoretical work for square wave voltammetry at the dropping mercury electrode is given. Experiments using ferric oxalate and cadmium (II) in HC1 confirm excellent agreement with theory. Experimental peak heights and peak widths are found to be within 2% of calculated results. An example of trace analysis using square wave voltammetry at the dme is presented. The technique is shown to have the same order of sensitivity as differential pulse polarography but is much faster to perform. A detection limit for cadmium in 0.1 M HC1 for the system used here was 7 x 10 to the minus 8th power M.

Potassium Oxalate Inhibits Corrosion of Mild Steel by Ferric Ion

Abstract Potassium oxalate inhibits the corrosion of AISI 1010 steel in 2.5 pH H2SO4 solutions with and without Fe3+ ion at inhibitor efficiencies up to 98%. Ferric ion exerts a synergistic influence with oxalate ion. The minimum oxalate concentration required is directly proportional to the ferric ion concentration in solution. Inhibition is caused by 30.5 to 116.8 μ thick ferrous oxalate film, i.e., β-FeC2O4·2H2O, identified by X-ray diffraction analysis. Based on potential-time and current density-time curves, a three-stage mechanism for inhibition is postulated. Possible applications of this inhibitor in the mineral industry are suggested.

Effects of lipids on the activity of ferrochelatase

Removal of lipids from submitochondrial particles or detergent-solubilized mitochondrial preparations of rat liver resulted in a 90% loss of ferrochelatase (protochemeferro-lyase, EC 4.99.1.1) activity. The addition of either a fatty acid or phospholipid restored enzyme activity; the extent of reactivation being correlated with the degree of unsaturation of the fatty acid or acyl chain and independent of the polar head group of the phospholipid. Arrhenius plots of the ferrochelatase activities of submitochondrial particles and detergent-solubilized mitochondrial preparations showed transition temperatures of 37 and 28.5°C, respectively. Ferrochelatase of submitochondrial particles or detergent-solubilized preparations had an absolute requirement for Ca 2+. The ferrous salt of oxalic acid, a Ca 2+ chelator, was a very poor substrate for these preparations. In contrast, ferrochelatase activities of fatty acid- or lipid supplemented acetone extracts of these preparations were not dependent on the presence of Ca 2+ and ferrous oxalate served as substrate for these extracts.

Electroanalysis of iron in molten slags

It has been found, using chronopotentiometry, that ferric and ferrous ions in sodium disilicate at 950° C act as separate reducible species. The electrode processes have been examined and the diffusion coefficients have been determined. Using known weights of ferric oxide and ferrous oxalate in sodium disilicate glass, calibration curves have been obtained. These gave a good agreement between experimental and estimated values for mixtures of ferric and ferrous ions and suggest that the electroanalytical method could be suitable for the examination of ferric/ferrous ratios in steel-making slags.

The dependence on wavelength of 13C isotope effects in photolysis of aqueous solutions of ferrie oxalate

The formation of carbon dioxide by photolysis of aqueous solutions of ferric oxalate is accompanied by carbon isotopic fractionation. 12C appears preferentially in the evolved CO2, but the isotope effect depends markedly on the wavelength of the light used. Fractionation is essentially zero (k12/k13 = 1.001) at 366 nm, and increases with wavelength, reaching 1.050 at 520 nm. It is proposed that this variation of isotopic discrimination arises from the differing properties of the excited levels formed by photochemical activation.

Isotope effects measured by mössbauer spectrometry in ferrous oxalate and perchlorate

The influence of the substitution of H by D was investigated by means of the Mössbauer effect in the compounds FeC 2O 4 O 4·2H 2 O and Fe(ClO 4) 2·6H 2 O. Isomer shifts δ and quadrupole splittings ϵ were measured between 90 and 300 K. An important isotope effect dependent on temperature was observed for the value of ϵ in oxalate. Only a slight difference for the value of δ could be determined in perchlorate. The well-known transition of the perchlorate takes place at temperatures which differ by 4 K for the deuterated and hydrogenated compounds.

Chemical actinometry of ultraviolet laser radiation

The energy of nitrogen laser pulses (1.5×10–5 J) was measured by the chemical actinometry method, i.e., the amount of the products of photolysis of potassium ferric oxalate was determined photometrically. The quantum efficiency of photolysis induced by laser radiation was in good agreement with the quantum efficiency reported for conventional light sources.

The technique of step heating applied to thermal analysis

By use of the technique of step heating and a new type of sample holder, the undesirable effects caused by a number of external and internal factors in thermal analysis are eliminated. To point out the thermal effects appearing during sample decomposition, the thermograms were carried out without inert reference material. In function of the decomposition temperatures, thermal effects and the factors of the Arrhenius equation, the behaviour to decomposition of compounds was classified in five classes. By means of this classification is explained ideal and abnormal behaviour of the calcium oxalate monohydrate and respective of the ferrous oxalate dihydrate at the thermal decomposition in dynamic heating. This technique is applied to the study of the decomposition mechanism of the ferrous oxalate dihydrate and the decomposition temperatures and the activation energies were determined.

Studies on the formation of ?-Fe2O3 (maghemite) by thermal decomposition of ferrous oxalate dihydrate

The thermal decomposition of ferrous oxalate dihydrate FeC2O4.2H2O, has been investigated using thermogravimetric (TG), differential thermogravimetric (DTG), differential thermal analysis (DTA), X-ray diffraction and infra-red spectroscopic techniques. The DTA data obtained in air consist of an endothermic dehydration peak at ∼ 190‡ C and two exothermic peaks at ∼ 245 and ∼ 360‡ C. The first exotherm corresponds to the primary oxidative decomposition while the second one seems to be due to a structural transformation from a disordered or non-crystalline to a crystalline state ofα-Fe2O3. Similar experiments carried out using a nitrogen atmosphere show an endothermic peak ∼ 190‡ C followed immediately by an exothermic peak at 240‡ C. The final product of this decomposition has been identified as Fe3O4. The oxalate dihydrate containing traces of moisture decomposes in air under the ambient of its own gaseous products at ∼ 300‡ C to giveγ-Fe2O3. This compound has been characterized by X-ray diffraction and magnetic hysteresis measurements.

Emanation method for estimating reactivity of ferric oxides prepared from different sources

AbstractA method for estimating the reactivity of ferric oxide in solid state reaction processes is proposed. The temperature of the emanation curve maximum is taken as a characteristic parameter for the testing of the reactivity.The reactivity of ferric oxides prepared from ferrous sulphate, Mohr's salt (ferrous ammonium sulphate), ferrous oxalate and basic carbonate of iron by decomposition at 700°, 900° and 1100° has been studied. The results of the proposed method are compared with those of specific surface and catalytic activity measurements. The method is more objective and representative of the compound's ability to react with other solids.

Reaction of ortho-nitro-substituted benzene derivatives with ferrous oxalate

The reaction of ferrous oxalate with methyl 4-(o-nitrophenyl)butyrate, methyl o-nitrophenoxyacetate, o-nitrocumene, o-t-butynitrobenzene, NN-dimethyl-o-nitroaniline, o-nitroanisole, and nitrocyclohexane at 215–260° gave a variety of compounds, including cyclisation products and primary amines. Most of the results may be interpreted in terms of the formation of nitrene intermediates, although other mechanisms such as the dehydration of aci-nitro-tautomers, where these are possible, may be operative.

The conversion of azobenzenes to phenazines: A new molecular rearrangement

AbstractWhen azobenzenes arc heated with ferrous oxalate or with a fused mixture of aluminum chloride and sodium chloride the corresponding phenazines are formed in low yield. Azobenzene itself is exceptional in giving benz[c]cinnoline with AlCl3‐NaCl. Azoxybenzenes and ferrous oxalate give azobenzenes and some phenazines, while azoxybenzene itself also gives 2‐hydroxyazobenzene via a Wallach‐type rearrangement. The rearrangements are thought to occur at the surfaces of the reagent. No rearrangement to the phenazines occurs in the absence of the reagent.