Determination Of Fe3 Research Articles

Determination of Fe3+ sites in a NaFeSi2O6 glass by neutron diffraction with isotopic substitution coupled with numerical simulation

Isotopic substitution in neutron diffraction combined with empirical potential structure refinement simulations has been employed to probe the sites occupied by Fe3+ and Fe2+ in a NaFeSi2O6 glass. This study reveals the presence of two populations of Fe3+ sites. 95% of Fe3+ is in tetrahedral sites (dFe3+–O=1.866±0.001Å), as the remainder ferric iron and ferrous iron (∼20% of total Fe) are five coordinated.

Investigation of the Mixing Efficiency of a Chaotic Micromixer Using Thermal Lens Spectrometry

This work investigates the efficiency of a chaotic micromixer using thermal lens spectrometry. The outlet of the mixing device was connected to a thermal lens detection head integrating the probe beam optical fibers and the sample capillary. The chaotic micromixer consisted of a Y-shaped poly(dimethylsiloxane) (PDMS) microchip in which ribbed herringbone microstructures were etched on the floor of the main channel. Due to the solvent composition dependence of the thermal lens response, the photothermal method was shown to be highly sensitive to nonhomogeneous mixing compared to fluorescence detection. The apparatus was applied to the determination of Fe2+ with 1,10-phenanthroline using flow injection analysis; a limit of detection of 11 microg L(-1) of iron was obtained.

Partitioning of ferric and ferrous iron between plagioclase and silicate melt

Using the thermodynamic algorithm of Sugawara (Contributions to Mineralogy and Petrology 141, 2001, p. 659–686), FeO and Fe2O3 concentrations in plagioclase were computed for 420 published experiments on tholeiitic, FeTi-tholeiite, calc-alkaline, and alkaline magma compositions. Estimates of the partition coefficient between plagioclase and liquid range from 0.19 to 0.92 for Fe2O3 and from 0.008 to 0.050 for FeO, i.e. ca. twenty times greater for Fe2O3 than for FeO. Partitioning of Fe2O3 and FeO is independent of both oxygen fugacity and plagioclase composition, contradicting the common assumption that partitioning of Fe2O3 correlates positively with the amount of aluminium in plagioclase. In contrast, the SiO2-content of the magma correlates positively with the partition coefficients for Fe2O3 and FeO. This is ascribed to increasing activity of iron in polymerised SiO2-rich magma. Advances of micro-beam Fe-XANES techniques allow the determination of Fe3+/ΣFe in plagioclase. Using such plagioclase data and the partition coefficients for Fe2O3 and FeO, the Fe2O3/FeO and oxygen fugacity of equilibrium magma may be estimated. As petrological examples, we estimate that the oxygen fugacity of the Palisades sill ranged from the QFM buffer to 0.5 log unit below it (QFM to QFM –0.5), the Lake County basalt from QFM to QFM –2, and Upper Zone a of the Skaergaard intrusion from QFM –1 to QFM –1.5.

Determination of Fe2+ in Rice Leaves (Oryza sativa L.) by Using the Chelator BPDS Alone or Combined with the Chelator EDTA

Iron toxicity is a problem in many areas of wetland rice. Since Fe2+ is considered to be the toxic form of iron, the objective of this research was to determine the Fe2+ concentration in rice leaves using the chelator bathophenanthroline disulfonate (BPDS), disodium salt alone or combined with the chelator ethylenediaminetetraacetate (EDTA), disodium salt, where BPDS should solely chelate the Fe2+ and EDTA chelate only Fe3+. Thus, the combination of these chelators should stabilize the Fe oxidation states. It was also tested whether the chelators BPDS and EDTA could stabilize the oxidation states of Fe during the extraction of rice leaves. Extractions of rice leaves were carried out using an 1 mM BPDS or BPDS‐EDTA extractant solution. To test the stabilization of the Fe oxidation states by the combination of BPDS with EDTA, the extraction solution for one part of the samples contained 0.07 mM Fe3+. An extraction without plant material as control was also taken into consideration. The results indicated that the chelators were able to stabilize the oxidation states of Fe in the control (extraction without plant material). However, in the presence of plant material, Fe3+ was partly reduced to Fe2+, i.e., the chelators could not stabilize the oxidation states of Fe. Accordingly, we concluded that the BPDS‐EDTA method may function for the Fe2+ determination in water and soil, but it is apparently not suited for rice leaves.

Strong magnetic linear dichroism in Fe L23 and O K electron energy-loss near-edge spectra of antiferromagnetic hematite ?-Fe2O3

We report strong magnetic linear dichroism (MLD) at the Fe L 23 and O K edges of the antiferromagnetic compound hematite α-Fe2 O3 in high-resolution orientation- and temperature-dependent electron energy-loss spectroscopy (EELS). Large intensity differences of corresponding spectral features are observed when the Fe L 23 and O K edges are measured with momentum transfer either parallel or perpendicular to the magnetization. The resultant difference spectra for the Fe L 23 edges is consistent with the MLD observed in X-ray absorption spectroscopy. For the first time we have observed MLD at the O K edge, where the magnetic origin of this dichroism is demonstrated by temperature-dependent investigations across the Morin transition temperature T M = 263 K, at which the Fe electron spins, i.e. the magnetic moments, rotate by 90°. The O K edge MLD is interpreted in terms of superexchange between the spins of the Fe 3d and O 2p electrons through overlapping Fe 3d and O 2p orbitals. The experiments were performed in a transmission electron microscope (TEM), yielding information about the anisotropic electronic structure at nanoscale spatial resolution when operated with a focused electron probe. The effects of MLD at the Fe L 23 edges on the determination of Fe3+/ΣFe in hematite at submicrometre scale using different independent quantification methods are discussed.

Quantification of ferrous/ferric ratios in minerals: new evaluation schemes of Fe L 23 electron energy-loss near-edge spectra

Determination of Fe3+/ΣFe in minerals at submicrometre scale has been a long-standing objective in analytical mineralogy. Detailed analysis of energy-loss near-edge structures (ELNES) of the Fe L 23 core-loss edges recorded in a transmission electron microscope (TEM) provides chemical information about the iron oxidation state. The valence-specific multiplet structures are used as valence fingerprints. Systematic investigations on the Fe L 23 ELNES of mono and mixed-valence Fe-bearing natural minerals and synthetic solid solutions of garnets (almandine-skiagite and andradite-skiagite), pyroxenes (acmite-hedenbergite) and spinels (magnetite-hercynite) are presented where the presence of multiple valence states is distinguished by a splitting of the Fe L 3 edge. We demonstrate the feasibility of quantification of the ferrous/ferric ratio in minerals by analyzing the Fe L 23 ELNES as a function of the ferric iron concentration resulting in three independent methods: (1) The method of the modified integral intensity ratio of the Fe L 23 white lines employs two 2-eV-wide integration windows centring around both the Fe L 3 maximum for Fe3+ and the Fe L 2 maximum for Fe2+. This refined routine, compared to the previously published quantification method of the ferrous/ferric ratio in minerals, leads to an improved universal curve with acceptable absolute errors of about ±0.03 to ±0.04 for Fe3+/ΣFe ratios. (2) The second method uses a simple mathematical description of the valence-dependent splitting of Fe L 3 ELNES by fitting several Gaussian functions and an arctan function. The systematic analysis of the integral portions of the individual Gaussian curves for different mineral groups provides a further Fe3+/ΣFe quantification method with an absolute error of about ±0.02 to ±0.03. (3) The Fe L 3 ELNES can also be modelled with the help of reference spectra, whereby the Fe3+/ΣFe ratio can be determined with an absolute error of ca. ±0.02.

Fast Determination of Fe2+/Fe3+ Ratio in Ilmenite

Ilmenite (FeTiO3) is an initial raw material in titanium white manufacture. The Fe2+/Fe3+ ratio in ilmenite is measured before the sulphate technological process is started. The possibility of fast measurements of this ratio could help to control the manufacture process. A single-purpose Mossbauer effect analyser for the fast determination of Fe2+/Fe3+ ratio in ilmenite was built. The fast algorithm based on the calculation of a Fe2+/Fe3+ ratio from heights of spectral lines allowed to reduce the time of one analysis to ten minutes.

The single-purpose Mössbauer effect analyser for fast determination of Fe 2+ /Fe 3+ ratio in ilmenite

Ilmenite (FeTiO3) is an initial raw material in titanium white manufacture. The Fe2+/Fe3+ ratio in ilmenite is measured before the start of sulfate technological process. Possibility of fast measurements of this ratio could help to control manufacturing process. The single-purpose Mossbauer effect analyzer for fast determination of Fe2+/Fe3+ ratio in ilmenite was built.

Ferric iron content of mineral inclusions in diamonds from George Creek, Colorado determined using Mössbauer spectroscopy

The Mossbauer milliprobe allows the determination of Fe3+/ΣFe in samples as small as 50 μm. For the first time this technique is applied to a suite of diamonds of eclogitic paragenesis, where three garnet and five clinopyroxene inclusions in diamonds from George Creek, Colorado have been analysed. For garnet Fe3+/ΣFe ranges from 0–7%, while values for clinopyroxene range from 8–14%. These results are consistent with the low oxygen fugacity conditions implied by the presence of the inclusions in diamond.

Determination of Iron Oxidation State in Omphacites Applied to Geothermometry of Sudetic Eclogites

A common mineral geothermometer for eclogites is based on Fe2+-Mg exchange reaction between garnets and clinopyroxenes. For the accurate determination of Fe2+ in omphacites, ten omphacite samples were isolated from eight Sudetic eclogites and studied by electron microprobe and Mossbauer spectroscopy. Garnet-clinopyroxene equilibration temperatures for two Sudetic eclogites were calculated.

Refined Relationships between Chemical Composition of Dioctahedral Fine-Grained Micaceous Minerals and Their Infrared Spectra Within the OH Stretching Region. Part II: The Main Factors Affecting OH Vibrations and Quantitative Analysis

AbstractA new model for the interpretation of dioctahedral mica infrared (IR) spectra in the OH stretching vibration region is proposed. It is based on the analysis of the main factors responsible for the observed sequence of the OH frequencies. In terms of this model, the simple analytical dependence between the OH frequencies and the mass and valency of cations bonded to OH groups has been found. The specific character of the interaction between octahedral Al and OH groups in the mica structures is assumed.Integrated optical densities of the OH bands determined by the decomposition of the studied mica IR spectra are used for the quantitative analysis, that is, for the determination of a number of each type of octahedral cations per unit cell of the sample under study. A good agreement between the octahedral cation contents of 2:1 layers found from the IR spectra decomposition and the chemical analysis has shown that this technique may be used to study the local order-disorder of isomorphous cation distribution in mica structures.The essential result obtained by the quantitative analysis of the mica IR spectra is the determination of Fe3+ cations in the tetrahedral sites of some samples. This means that the conventional presentation of structural formulae for Al-Fe3+-containing 2:1 layer silicates is unacceptable without consideration of tetrahedral Fe3+ by spectroscopic techniques and by the quantitative analysis of the IR spectra, in particular.

Use of the respiration activity of Thiobacillus ferrooxidans for the specific determination of iron(II, III).

A method is described for the determination of Fe2+ and Fe3+ after its reduction to Fe2+ on the basis of oxygen uptake rate as a function of Fe2+ concentration. By using substrate-specific Thiobacillus ferrooxidans in combination with the standard addition method a specific determination of iron(II, III) is possible with the determination limit of 3 mumol/L.

Determination of Fe3+ and Fe2+ concentrations in feldspar by optical absorption and EPR spectroscopy

Ferrous and ferric iron concentrations in feldspars with low total iron content (<0.32 wt% total Fe) were determined from optical and electron paramagnetic resonance (EPR) spectra to better than ±15 percent of the amount present. Optical spectra indicate that Fe^(2+) occupies two distorted M-sites in plagioclases of intermediate structural state. The linear dependence of the Fe^(2+)/Fe total ratio on An content demonstrates that Fe^(2+) substitutes for Ca (not Na) so that the number of Ca-sites is a principal factor in iron partitioning in plagioclase. EPR powder spectra show that the number of sites for Fe^(3+) depends on structural state rather than on plagioclase chemistry. The observed linear correspondence of EPR double-integrated intensities with optical peak areas shows that all Fe^(3+) is tetrahedrally coordinated in both plagioclase and disordered potassium feldspar. Microcline perthites show, in addition to tetrahedral Fe^(3+), a signal due to axially coordinated ferric iron, which we associate with formation of hematite inclusions.

Doseamento espectrofotométrico de ferro (II) em medicamentos por complexação com ETTA

The ion Fe2+ in the drugs is complexed with ETTA in pH 4.5 and the absorbance of the formed complex is measuerd in 335 nm. This method presents excellent accuracy and the selectivity allows the determination of Fe2+ even in the presence of other metals and other chelating agents.

A Contribution to the Acid Cleaning of Boilers

AbstractThe dissolution rates of various types of magnetites are measured by a spectrophotometric technique allowing the determination of Fe3+/Fe2+ ratio as a function of time. Some tests are also performed on magnetite electrodes galvanically coupled to steel electrodes.The influence of copper on the dissolution rate of magnetite is evaluated and the effect due to the presence of organic corrosion inhibitors is determined.A circulating loop operating with some boiler tube electrodes was assembled in order to verify the possibility of monitoring the acid cleaning treatment by electrochemical measurements.Electrode potential‐time curves, polarization curves and polarization resistance data are recorded; the calculated corrosion rates are compared to weight‐loss data obtained in the same experimental conditions.From the overall results some conclusions are reached both on the dissolution process of magnetite and on the monitoring of the acid cleaning treatment.

Use of Magnetic Hyperfine Splitting to Determine Fe2+/Fe3+ Ratios in Complex Silicate Minerals

THE determination of Fe2+/Fe3+ ratios in complex multi-component minerals poses a difficult and recurring problem for mineralogists. Conventional wet methods of analysis are difficult and they are commonly subject to errors that result from the accidental oxidation of Fe2+ while the specimen is being dissolved. Such methods can give no information concerning relative site occupancy among the various distinguishable crystallographic sites, which is often of interest. Consequently, attempts have been made to develop nondestructive methods of obtaining the desired information; of these, Mossbauer spectroscopy has been most prominent1,2.

Dosage Spectrophotométrique du Fer Ferreux en Présence D'un Excès de fer Ferrique, et du fer Ferrique En Présence D'Un Excès De Fer Ferreux

AbstractThe spectrophotometric determination of traces of Fe2+ in a large excess of Fe3+ (⩽ 10–1 M) and the determination of Fe3+ in an excess of Fe2+ (⩽ 10−1 M) is described. Fe2+ is determined with o‐phenanthroline at pH ≅ 3 after complexation of the Fe3+ ions with fluoride. 2,2'‐bipyridyl gives better results than o‐phenanthroline in presence of ClO4 ions. Elimination of Fe3+ as Fe(OH)3 at pH ≅ 7 is also possible.Fe3+ is determined in an acid solution by a modified sulfocyanide method, corrected for an increase in absorbance after the addition of the colorimetric reagent.