Determination Of Ferrous Iron Research Articles

Novel application of the X-ray fluorescence method for the determination of FeO content for reference materials characterization

Novel X-ray fluorescence technique is applied for determination of ferrous iron (FeO) content for reference material characterization in addition (or as alternative) to volumetric method. Approach is based on the dependence of FeKβ5 line relative intensity on the iron valence state. A set of 99 reference materials was studied to choose optimal calibration set containing rocks of different composition: ultrabasic, basic, intermediate, and acid igneous rocks, silicate sedimentary and metamorphic rocks. The ratio of FeKβ5 and FeKβ1,3 lines intensities was chosen as analytical parameter. A set of 40 GeoPT samples was analyzed, and it was shown that the uncertainty of proposed X-ray fluorescence technique is comparable to one of certified volumetric (potassium dichromate titration) technique for the samples with Fe2O3tot content more than 1wt%. The presence of Sr and Co in usual for rocks content (up to ∼0.23wt% and ∼200μg/g respectively) does not affect to the measurement uncertainty. Analytical potential, limitations and features of proposed technique are discussed.

The environmental importance of iron speciation in soils: evaluation of classic methodologies

Iron is an essential mineral and one of the most abundant in soils, presenting itself in the environment as ferrous and ferric ions. As each oxidation state of iron has a different role in the environment, its speciation in environmental studies is important. The determination of ferrous iron received great attention from soil chemists because of its important role in agriculture, in redox processes, and as an electron acceptor in the catalysis of organic matter. Methodologies with the use of colorimetric reagents to determine ferrous iron are divergent and not very clear. In this study, we compared two colorimetric reagents (1,10-phenanthroline and ferrozine) to determine the total concentration of iron, ferrous and ferric ions in soil, using simple and low-cost methodologies. The determination of ferrous and total iron with 1,10-phenanthroline colorimetric reagent, following published instructions, did not correlate with ferrozine method, presenting an erroneous quantification. After neutralizing the extract of 1,10-phenanthroline with NaOH, both colorimetric methods allowed to quantify with precision and high yield the amount of ferrous and total iron extracted from the soil. The oxidation states of iron have a different contribution and importance to the environment. In this sense, the improvement of a widely used methodology is crucial for the better study of iron speciation in soil.

Determination of Ferrous Iron in Ferric Chloride Hexahydrate

Objective: As a pharmaceutical raw material, ferric chloride hexahydrate has been included in the British Pharmacopoeia, the European Pharmacopoeia (2008) and the United States Pharmacopoeia (2015), and there are detailed discussions on quality standards and testing methods. Ferric chloride hexahydrate has not been included in the Chinese Pharmacopoeia. This study is the part of research to establish a spectrophotometric method for the determination of ferrous iron in ferric chloride hexahydrate. In this study, the two methods were discussed in detail, and the spectrophotometric method for detecting the content of ferrous iron in ferric chloride hexahydrate was proposed. Methods: The detection method on ferrous iron in ferric chloride hexahydrate among European pharmacopoeia, United States pharmacopoeia and Chemical Reagent Ferric Chloride Hexahydrate (HG/T3474-2014) of China's Chemical Industry were compared. The last two methods were not easy to operation. On the basis of the European pharmacopoeia, a method was proposed that after Fe³⁺ were screened with H3PO4, Fe2+ was measured by spectrophotometry, and the method was verified by experiments. Results and Conclusion: The spectrophotometry method is easy to operate and has good reproducibility. The content of ferrous iron can be calculated semi-quantitatively by masking ferric iron with H3PO4 and spectrophotometric determination of ferrous ion content. Therefore, the method established in this study can more clearly detect whether the ferrous content in ferric chloride hexahydrate is up to standard.

Online Flow‐Based Spectrophotometric Determination of Ferrous Iron Mass Fraction and Total Iron Mass Fraction in Twenty‐Seven Rock Reference Materials Using a Schlenk line Technique

We developed an online continuous‐flow spectrophotometric method for determination of ferrous iron and total iron mass fractions in various types of geological certified reference materials (CRMs) using a Schlenk line technique to exclude oxygen during the digestion process. The continuous‐flow technique enabled automatic, reliable and real‐time analysis, and decreased sample and reagent consumption. The Schlenk line expels air to prevent oxidation during sample digestion. Compared with traditional spectrophotometric procedures, this analytical procedure is easier, more automated and more accurate. The composition of the acid matrix and time used to dissolve the samples were carefully examined. The procedure was tested on 186 replicates of twenty‐seven rock CRMs, and the results showed good agreement with the compiled values from the literature. Based on the statistical data, the proposed procedure was found to be accurate within 0.12% m/m for ferrous iron mass fraction and 0.084% m/m for total iron mass fraction compared with the certified/recommended values. The proposed procedure is accurate, reproducible and has a high throughput (ten samples per hour).

An Iron Determination Method for Azo Dyes-Contaminated Wastewater

We have designed an improved iron determination method based on the ability of ferrous iron to reduce 12-molybdophosphate (12-MP). The method allows for direct determination of ferrous iron in the presence of azo dyes. The iron determination method had a specific extinction coefficient of 0.0514 (mg l-)-1.cm-1 at 865 nm with a correlation coefficient of 0.999. The relative standard deviation for each data point does not exceed 5% (n=3) suggesting precision. In its oxidized state 12-MP is yellowish in color and when reduced it forms a blue solution. The iron determination method is less interfered with azo dyes compared to common iron determination methods such as 1,10-phenanthroline and the commercial FerreMoTM.

An Iron Determination Method for Azo Dyes-Contaminated Wastewater


 We have designed an improved iron determination method based on the ability of ferrous iron to reduce 12-molybdophosphate (12-MP). The method allows for direct determination of ferrous iron in the presence of azo dyes. The iron determination method had a specific extinction coefficient of 0.0514 (mg l-)-1.cm-1 at 865 nm with a correlation coefficient of 0.999. The relative standard deviation for each data point does not exceed 5% (n=3) suggesting precision. In its oxidized state 12-MP is yellowish in color and when reduced it forms a blue solution. The iron determination method is less interfered with azo dyes compared to common iron determination methods such as 1,10-phenanthroline and the commercial FerreMoTM.

Precise determination of ferrous iron in silicate rocks

We have developed a highly precise method for the determination of ferrous iron (Fe2+) in silicate rocks. Our new method is based on Wilson’s procedure (1955) in which surplus V5+ is used to oxidize Fe2+ into Fe3+ while equivalently reducing V5+ into V4+. Because V4+ is more resistant to atmospheric oxidation than Fe2+, Fe2+ in the sample can be determined by measuring unreacted V5+ by adding excess Fe2+ after sample decomposition and then titrating the unreacted Fe2+ with Cr6+. With our method, which involves conditioning the sample solution with 5 M H2SO4 in a relatively small beaker (7 mL), the oxidation of Fe2+ or V4+ that leads to erroneous results can be completely avoided, even in 100-h sample decompositions at 100°C. We have measured the concentration of FeO in 15 standard silicate rock powders provided by the Geological Survey of Japan (GSJ). Analytical reproducibility was better than 0.5% (1σ) for all but those samples that had small amounts of Fe2+ (<1.5 wt.% of FeO). Fourteen of these samples gave FeO contents significantly higher than the GSJ reference values. This likely indicates that the GSJ reference values, obtained by compiling previously published data, contain a large number of poor-quality data obtained by methods with lower recovery of Fe2+ caused by oxidation or insufficient sample decomposition during analyses. To achieve accurate determinations of Fe2+ in our method, several factors besides the oxidation must be considered, including: (1) long-term variations in the concentration of Fe2+ solution must be corrected; (2) excess use of the indicator must be avoided; and (3) the formation of inert FeF+ complex must be avoided during titration when using boric acid as a masking agent.

Semiautomatic determination of ferrous iron in iron ore using a flow-injection technique

A semiautomatic method for mineral-phase analysis for ferrous iron (FeCO3) using on-line leaching technique was developed. A flow-injection manifold is described, which makes on-line leaching of the powdered sample followed by color developing of Fe(II) with o-phenanthroline and its spectrophotometric determination possible. This method can produce meaningful results provided that the experimental conditions are kept at optimum values. The analysis time is greatly reduced by using flow injection techniques. Sample throughput was about 12 samples/hr with a method precision of 2.7% RSD, depending on the leaching time chosen and FeCO3 content in ores. Analytical data were in good agreement with recommended values for analysis of standard references materials. For each analysis, 20–30 mg of powdered sample was required. © 2000 John Wiley & Sons, Inc. Lab Robotics and Automation 12:86–90, 2000

Monitoring Corrosion in Boiler Systems with Colorimetric Tests for Ferrous and Total Iron

Because of the low oxygen conditions that prevail in industrial boiler systems, active corrosion releases soluble corrosion products that contain iron in the ferrous, Fe(II), oxidation state. Active corrosion can be detected throughout boiler systems by colorimetric determination of ferrous iron. Ferrous iron measurements are particularly useful for detecting corrosion in once-through components such as feedwater (FW) systems. The same approach is equally valuable for detecting internal boiler corrosion when accurate information on cycles of concentration is available. Ferrous iron testing also can differentiate the dispersion of iron oxide particulates in the FW from corrosion of the boiler internals. Corrosion mechanisms that generate ferrous iron species are discussed as well as the interpretation of data obtained by total iron testing.

Determination of ferrous iron in rock and mineral samples by three volumetric methods

SAIKKONEN, RISTO J. and RAUTIAINEN, IRJA A. 1993. Determination of ferrous iron in rock and mineral samples by three volumetric methods. Bull. Geol. Soc. Finland 65. Part 1, 59-63. Ferrous iron was determined by three volumetric methods in 13 in-house reference rock samples and in 31 international geological reference samples. The methods used were Amonette & Scott' s oxidimetric method, Wilson's oxidimetric method and Pratt's method. The results for FeO by these volumetric methods in 13 in-house rock samples were compared to the results obtained in other analytical laboratories in Finland. The results for FeO in the international samples were compared with published data. The results show that Pratt's method is the most reliable of the methods tested.

Biotite and garnet compositional variation and mineral equilibria in Grenville gneisses of the Otter Lake area, Quebec

Garnet‐biotite gneisses, some of which contain sillimanite or hornblende, are widespread within the Otter Lake terrain, a portion of the Grenville Province of the Canadian Shield. The metamorphic grade is upper amphibolite to, locally, lower granulite facies.The atomic ratio Fe2+/(Fe2++ Fe3+) in biotite ranges from 0.79 to 0.89 (ferrous iron determinations in 10 highly pure separates), with a mean of 0.86. Mg and Fe2+ atoms occupy 67–78% of the octahedral sites, the remainder are occupied by Fe3+, Ti, and Al, and some are vacant. Mg/(Mg + Fe2+), denoted X, in the analysed samples ranges from 0.32 to 0.65. Garnet contains 1–24% grossular, 1–12% spessartine and X ranges from 0.07 to 0.34.Compositional variation in biotite and garnet is examined in relation to three mineral equilibria:(I) biotite + sillimanite + quartz = garnet + K‐feldspar + H2O;(II) pyrope + annite = almandine + phlogopite;(III) anorthite = grossular + sillimanite + quartz.Measurements of X (biotite) and X (garnet) are used to construct an illustrative model for equilibrium (I) which relates the observed variation in X to a temperature range of 70°C or a range in H2O activity of 0.6; the latter interpretation is preferred.In sillimanite‐free gneisses, the distribution of Mg and Fe2+ between garnet (low in Ca and Mn) and biotite is adequately described by a distribution coefficient (KD) of 4.1 (equilibrium II). The observed increase in the distribution coefficient with increasing Ca in garnet is ln KD= 1.3 + 2.5 × 10−2 [Ca]where [Ca] = 100 Ca/(Mg + Fe2++ Mn + Ca). The distribution coefficient is apparently unaffected by the presence of up to 12% spessartine in garnet.In several specimens of garnet‐sillimanite‐plagioclase gneiss, the Ca contents of garnet and of plagioclase increase in unison, as required by equilibrium (III). The mean pressure calculated from these data (n= 17) is 5.9 kbar, and the 95% confidence limits are ±0.5 kbar.

A new spectrophotometric method for the determination of ferrous iron in the presence of ferric iron

AbstractA new spectrophotometric method for the determination of ferrous iron concentration in samples containing ferric iron is presented. This new method is a modification of the Muir o‐phenanthroline ferrous iron determination method.The new method consists of the quantitative spectrophotometric determination of Fe(II) by o‐phenanthroline, but in which the ferric iron is complexed with sodium fluoride to eliminate interferences.A critical experimental comparison between the Muir spectrophotometric method, the Kolthoff titrametric method and the new proposed method is presented. Whenever Fe(III) accounts for more than 50% of the total iron in a sample, the method of Muir overestimates Fe(II).The proposed method has a range of 1–10 μg ferrous iron. It is as insensitive to other metal ions as the original method of Muir and is insensitive to Fe(III) up to a point where Fe(III) might be as high as 95% total iron.The proposed method is suitable for Fe(II) determination in bacterial leaching systems, where Fe(II) might be as low as 1% of total iron.

Melt densities in the Na 2O-FeO-Fe 2O 3-SiO 2 system and the partial molar volume of tetrahedrally-coordinated ferric iron in silicate melts

Abstract The densities of 12 melts in the Na 2 O-FeO-Fe 2 O 3 -SiO 2 system have been determined in equilibrium with air, in the temperature range of 1000–1500°C, using the double bob, Archimedean technique. Ferrous iron determinations of 100–200 mg samples, “dip” quenched from high temperature, indicate that all the melts investigated were highly oxidized under these experimental conditions. 57 Fe Mossbauer spectra of glasses obtained by drop quenching 80 mg melt samples from loop equilibration runs yield Fe 3+ /Fe 2+ data equivalent to that for the densitometry (dip) samples for all but the most viscous melt, and confirm that all but one melt equilibrated with air during the densitometry measurements. Melt densities range from 2.17 to 2.88 g/cm 3 with a mean standard deviation (from replicate experiments) of 0.36%. Least squares regression of the density data at 1300, 1400 and 1500°C, was calculated, both excluding and including excess volume terms (herein named linear and nonlinear fits, respectively) and the root mean squared deviation (RMSD) of each regression was compared with the total experimental error. The partial molar volumes computed for linear fits for Na 2 O and SiO 2 are similar to those previously reported for melts in the Na 2 O-Al 2 O 3 -SiO 2 system ( Stein et al ., 1986). The partial molar volumes of Fe 2 O 3 obtained in these linear fits are equal to those obtained by Shiraishi et al . (1978) in the FeO-Fe 2 O 3 -SiO 2 system but 5 to 10% lower than reported by Mo et al . (1982) in multicomponent melts. The partial molar volume exhibited by Fe 3+ in this system is representative of the partial molar volume of tetrahedrally coordinated Fe 3+ in silicate melts.

Simple Spectrophotometric Determination of Ferrous Iron in Twelve French Geochemical Reference Standards

Iron (II) oxide in silicate rocks can readily be measured after digestion with HF and HCl by reaction with KI and KIO3. The iodine produced during the digestion is trapped in CCl4 and measured at 512 nm spectrophotometrically. Results for ten accepted and two new geochemical reference standards are presented.

Determination of ferrous iron in silicate rocks

Abstract Present-day rock analyses commonly are deficient because FeO and other constituents (H 2 O and CO 2 ), which are not amenable to instrumental analysis, are not determined. Ferrous iron, however, can be determined with good precision in most silicate rocks by a simple, rapid, and inexpensive method using a fused-silica flask in place of a large Pt crucible for sample dissolution. Comparative data on 18 standard reference samples are given.

Chelating agent differences in ferrous iron determinations

Abstract Experiments were conducted to test the ability of ferrous iron (Fe2+) chelating agents to discriminate between Fe2+ and ferric iron (Fe3+), to determine ranges of Fe2+ detection in reactions, to determine interactions of chelating agents with phosphorus (P) which is common in plant tissue, and to evaluate some of the complexities of methodology for Fe2+ determinations. PDTS [ferrozine; 3‐(2 pyridyl)‐5,6‐bis (4‐phenyl‐sulfonic acid)‐l,2,4‐triazine] reacted with only small amounts of Fe3+, had a fairly wide range of Fe2+ detection (0–200 μg), P did not interfere with the reaction, and methodology was relatively simple. TPTZ [2,4,6‐tripyridyl‐s‐triazine] was very specific for Fe2+, did not react with Fe3+, had a relatively narrow range of Fe2+ detection (0–40 μg), P did not interfere with the reaction, and methodology was relatively simple. BPDS [4,7‐diphenyl 1.10‐phenanthrolinedisulfonic acid] reacted with a small amount of Fe3+, had a fairly wide range of Fe2+ detection (40–200 μg), did not react ...

Determination of ferrous iron in copper-process metallurgical solutions by the o-phenanthroline colorimetric method

Determination of ferrous iron in copper-process metallurgical solutions by the o-phenanthroline colorimetric method

The determination of ferrous iron in natural waters with 2,2′ bipyridyl

Measurements of ferrous iron, in water containing both ferrous and ferric iron, by the 2,2′ bipyridyl method and polarography are compared. When samples are protected from strong solar irradiation and contact with air, and measurements are made quickly, the 2,2′ bipyridyl method can distinguish the oxidation states of iron in anoxic waters containing ferrous iron.

A study of Wilson's determination of ferrous iron in silicates

The chemical factors affecting the accuracy of Wilson's procedure for determination of ferrous iron in silicates have been investigated. This procedure utilizes pentavalent vanadium to oxidize ferrous iron as it is set free from the silicate by hydrofluoric acid. The quadrivalent vanadium produced is more resistant to oxidation by oxygen than ferrous iron, and conserves the reducing power of the silicate. The procedure is done at room temperature. Recovery of ferrous iron under various conditions has been studied to elucidate the chemical mechanisms of loss in the procedure. Some improvements have been made. The studies indicate that the procedure is of high accuracy. An effect resulting in loss of ferrous iron titre has been found, involving the chemical attack of solids by solutions containing oxygen and pentavalent vanadium. This loss does not appear to take place if all ion species are in solution.

Direct determination of ferrous iron in silicate rocks and minerals by iodine monochloride

Direct determination of ferrous iron in silicate rocks and minerals by iodine monochloride