Chromous Ion Research Articles

Chromous capacities of ferrochromium and matte smelting slags

Purpose: of this paper is to extend the slag capacity concept to sparingly soluble cationic species encountered for example in matte smelting and ferrochromium processing in terms of chromous capacities. Design/methodology/approach: In this context in order to develop the chromous capacity the experimental data on slag-metal equilibrium for ferrochromium smelting and on chromium distribution between slag and matte phases encountered in sulphide smelting of PGM (Platinum Group Metals) and chromium containing copper nickel concentrates were used. Findings: The calculated chromous capacities were in the 10-8 range for ferrochrome smelting slags and 10-4 range for matte smelting slags. These values indicate the very low and moderate chromous ion dissolving ability of ferrochromium smelting slags and matte smelting slags respectively. Research limitations/implications: Due to highly reducing conditions in ferrochromium smelting and the imposed low oxygen partial pressures in sulphide smelting of chromium and PGM containing concentrates chromium in the slag was assumed to be in its divalent state. The slag-metal/matte reaction for dissolution of chromium into the slag as a cation under reducing conditions -in contrast to reactions for dissolution of species such as sulphur and phosphorus into the slag as anions under oxidizing conditions – required the release of electrons. Thus to maintain charge neutrality the dissolution of chromium from the metal or the matte phases into the slag as Cr2+ ions was accompanied by consumption of these electrons by reduction of Fe2+ ions in the slag into metallic Fe which dissolved in the metal/ matte phase. This was supported by the experimental equilibrium data. Hence the slagmetal/ matte reaction defining the chromous capacity involved both O2- and Fe2+ ions of the slag phase. Moreover for matte smelting the thermodynamic activities of species in the matte phase were assumed to conform to ideal associated solution model due to lack of data. For future work it is advisable to determine such activities. Practical implications: The calculated chromous capacities were in the 10-8 range for ferrochrome smelting slags and 10-4 range for matte smelting slags. The results clearly indicate that in matte smelting lower basicity slags would be preferable to render chromium more soluble in the slag in contrast to ferrochromium smelting where higher basicity slags would be suitable to minimize chromium losses to the slag. Originality/value: This research and hence the paper is probably the first on dissolution of chromium as chromous ion in slags, thus it is novel and original.

Two-Coordinate, Quasi-Two-Coordinate, and Distorted Three Coordinate, T-Shaped Chromium(II) Amido Complexes: Unusual Effects of Coordination Geometry on the Lowering of Ground State Magnetic Moments

The synthesis and characterization of the mononuclear chromium(II) terphenyl substituted primary amido-complexes Cr{N(H)Ar(Pr(i)(6))}(2) (Ar(Pr(i)(6)) = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-(i)Pr(3))(2) (1), Cr{N(H)Ar(Pr(i)(4))}(2) (Ar(Pr(i)(4)) = C(6)H(3)-2,6-(C(6)H(3)-2,6-(i)Pr(2))(2) (2), Cr{N(H)Ar(Me(6))}(2) (Ar(Me(6)) = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Me(3))(2) (4), and the Lewis base adduct Cr{N(H)Ar(Me(6))}(2)(THF) (3) are described. Reaction of the terphenyl primary amido lithium derivatives Li{N(H)Ar(Pr(i)(6))} and Li{N(H)Ar(Pr(i)(4))} with CrCl(2)(THF)(2) in a 2:1 ratio afforded complexes 1 and 2, which are extremely rare examples of two coordinate chromium and the first stable chromium amides to have linear coordinated high-spin Cr(2+). The reaction of the less crowded terphenyl primary amido lithium salt Li{N(H)Ar(Me(6))} with CrCl(2)(THF)(2) gave the tetrahydrofuran (THF) complex 3, which has a distorted T-shaped metal coordination. Desolvation of 3 at about 70 °C gave 4 which has a formally two-coordinate chromous ion with a very strongly bent core geometry (N-Cr-N= 121.49(13)°) with secondary Cr--C(aryl ring) interactions of 2.338(4) Å to the ligand. Magnetometry studies showed that the two linear chromium species 1 and 2 have ambient temperature magnetic moments of about 4.20 μ(B) and 4.33 μ(B) which are lower than the spin-only value of 4.90 μ(B) typically observed for six coordinate Cr(2+). The bent complex 4 has a similar room temperature magnetic moment of about 4.36 μ(B). These studies suggest that the two-coordinate chromium complexes have significant spin-orbit coupling effects which lead to moments lower than the spin only value of 4.90 μ(B) because λ (the spin orbit coupling parameter) is positive. The three-coordinated complex 3 had a magnetic moment of 3.79 μ(B).

ChemInform Abstract: Synthesis of Pyrrolopyrimidones by a Chromous Ion Mediated Reductive Cyclization.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Emission quenching of binuclear pyrophosphito platinum(II) complexes in aqueous solution by sulphur dioxide. Spectroscopic measurements on sulphur dioxide addition and chromous ion reduction

Abstract The emission intensity at 517 nm from Pt2(pop)44− (pop = P2O5H22−) is quenched by the addition of sulphur dioxide. The sulphur dioxide coordinates at the axial platinum(II) sites by a η1-SO2 bond. This coordination is supported by 31p NMR and Raman spectroscopy of aqueous solutions. The electronic spectrum of a sulphur dioxide saturated solution of Pt2(pop)44− shows an absorption at 428.5nm (∈ = 4.1 × 104). From the decrease in the chromophore for uncomplexed Pt2(pop)44− the equilibrium constant for SO2 binding is estimated to be 1.74 M2l−2. The effect of adding different quenchers to aqueous solutions of Pt2(pop)44− is discussed. The compound Pt2(pop)44− will undergo 2-electron reduction with chromous ion.

Conformation change of cytochrome c: I. Ferrocytochrome c structure refined at 1·5 Å resolution

Tuna ferrocytochrome c has been crystallographically refined at a resolution of 1.5 Å using the Diamond real-space method followed by Jack-Levitt restrained energy and reciprocal space refinement, monitoring progress continuously with superimposed Fourier and difference Fourier maps: The final R factor for cytochrome plus 53 solvent molecules, using 13,840 reflections with intensities greater than 2 σ, is 17·3%. The overall structure remains as described earlier (Takano et al., 1977), but structural details have been clarified to the point where meaningful comparison can be made with the oxidized molecule (following paper). Main and side-chain flexibility as judged by isotropic temperature parameters correlate with position in the molecule, with greatest flexibility at external chain loops. The haem group is held tightly in place by its attachments and neighbours, and is deformed slightly into a saddle shape. The iron does not deviate significantly from the best mean plane of the haem, and bond lengths to ligands are as expected from model compounds. A water molecule buried in the haem crevice is bonded to Asn52, Tyr67 and Thr78, the latter two being bonded also to Met80 and the outer haem propionate. It is proposed that this buried water molecule is involved in the reduction of ferricytochrome c by chromous ion, and the reactions of Tyr67 with KI 3 and tetranitromethane. Two other buried water molecules occur beneath the 20's loop at the right, and within the 40's loop at the bottom. Reasonable if tentative functional assignments can be made for all 24 of the evolutionarily invariant residues in the cytochrome molecule.

Chromium(III) products from the reduction of 1,4-benzoquinone by chromous ion. Synthesis of the .mu.-oxo-bis(pentaaquochromium(III)) ion

Chromium(III) products from the reduction of 1,4-benzoquinone by chromous ion. Synthesis of the .mu.-oxo-bis(pentaaquochromium(III)) ion

A new series of organochromium complexes formed in aqueous solutions

Chromous ion reacts with 3-pyridineacrylic acid, 4-pyridineacrylic acid, maleic acid and fumaric acid to give remarkably inert organochromium(III) species. These species were isolated by ion exchange from acidic aqueous media and were characterized by a variety of techniques. An organochromium(III) compound was even isolated from the Cr(III)-3-pyridineacrylic acid aqueous mixture in solid form. In all the organometallic compounds reported in this paper chromium(III) is believed to be σ-bonded to carbonyl by the general scheme ▪.

ChemInform Abstract: THE ONE‐ELECTRON REDUCTION OF CARBONIUM IONS. PART 13. THE CONFORMATIONAL EFFECTS OF CYCLOPROPYL, ISOPROPYL, AND PHENYL SUBSTITUENTS FLANKED WITH METHYL GROUPS ON THE REDUCTION RATE OF THE TROPYLIUM ION WITH THE CHROMOUS ION

Chemischer InformationsdienstVolume 10, Issue 41 Preparative Organic Chemistry ChemInform Abstract: THE ONE-ELECTRON REDUCTION OF CARBONIUM IONS. PART 13. THE CONFORMATIONAL EFFECTS OF CYCLOPROPYL, ISOPROPYL, AND PHENYL SUBSTITUENTS FLANKED WITH METHYL GROUPS ON THE REDUCTION RATE OF THE TROPYLIUM ION WITH THE CHROMOUS ION K. TAKEUCHI, K. TAKEUCHISearch for more papers by this authorK. KOMATSU, K. KOMATSUSearch for more papers by this authorK. YASUDA, K. YASUDASearch for more papers by this authorF. MIKUCHI, F. MIKUCHISearch for more papers by this authorK. OKAMOTO, K. OKAMOTOSearch for more papers by this author K. TAKEUCHI, K. TAKEUCHISearch for more papers by this authorK. KOMATSU, K. KOMATSUSearch for more papers by this authorK. YASUDA, K. YASUDASearch for more papers by this authorF. MIKUCHI, F. MIKUCHISearch for more papers by this authorK. OKAMOTO, K. OKAMOTOSearch for more papers by this author First published: October 9, 1979 https://doi.org/10.1002/chin.197941126AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume10, Issue41October 9, 1979 RelatedInformation

Automated Urease-Chromous Method for Determining Nitrogen in Fertilizers

Abstract An automated urease-chromous colorimetric method (AUCM) has been developed for determining nitrogen in fertilizers. The method is applicable to fertilizer samples that contain only ammoniacal, nitrate, and urea nitrogen. The concept of this method, combining nitrate reduction and enzymatic urea hydrolysis to produce a single method for total nitrogen, is new. The AUCM is an almost totally automated method with only an acidic dissolution step as the manual sample preparation. The urea is hydrolyzed to ammonia and carbon dioxide with urease, and the nitrate is reduced to ammonia with chromous ion within the continuous flow analytical system. The final step, also within the analytical system, is the spectrophotometric measurement of the ammonia, employing the ammonia-salicylate-hypochlorite chemistry. The sampling rate is 30 samples/hr. The method is not applicable to fertilizer samples containing refractory organic nitrogen forms, water-insoluble nitrogen, or significant levels of biuret. The average per cent nitrogen recovery by the AUCM for ammonium nitrate-diammonium phosphate bulk-blended fertilizer samples was 99.7, suspensions and liquids 99.7, urea fertilizers 97.8, and urea-diammonium phosphate bulk blends 98. The relative standard deviation for the analytical system was 0.40%, and for the method, 0.70%. The sample preparation is short and simple. This method offers many advantages as a screening method for fertilizer industry and control laboratories.

The one-electron reduction of carbonium ions. Part 13. The conformational effects of cyclopropyl, isopropyl, and phenyl substituents flanked with methyl groups on the reduction rate of the tropylium ion with the chromous ion

Methyl-, phenyl-, cyclopropyl-, and isopropyl-tropylium ions and the respective tropylium ions with flanking methyl groups have been synthesized, and the second-order rate constants, k2, for the reduction of the tropylium ions with chromous ion have been determined in 10% hydrochloric acid at 25.0 °C. A linear free-energy relationship is observed when log k2 values for phenyl-, H-, and methyl-tropylium ions flanked with one [(2e), (1b), and (2b)] and also two methyl groups [(3e), (3a), and (3b)] are plotted against those for the corresponding ions without flanking methyls [(1e), (1a), and (1b)]. However, the log k2 values for cyclopropyl- or isopropyl-tropylium ions with flanking methyls [(2c), (3c), and (3d)] significantly deviate upward from the linear correlation lines, reflecting the loss of stabilization caused by restriction on the conformation of the isopropyl and cyclopropyl groups. A linear correlation has also been found between the log k2 values and the charge-transfer energies with pyrene for all the tropylium ions [(1a)–(3e)], indicating that the reducibility of the tropylium ions reflects the electron affinity inherent to the respective ions, irrespective of the presence or absence of the flanking methyl groups.

ChemInform Abstract: REDUCTION OF α‐KETO ACIDS BY LOW‐VALENT METAL IONS. 1. REACTION OF AQUEOUS CHROMOUS ION WITH PYRUVIC ACID

Chemischer InformationsdienstVolume 9, Issue 34 Preparative Organic Chemistry ChemInform Abstract: REDUCTION OF α-KETO ACIDS BY LOW-VALENT METAL IONS. 1. REACTION OF AQUEOUS CHROMOUS ION WITH PYRUVIC ACID J. KONSTANTATOS, J. KONSTANTATOSSearch for more papers by this authorN. KATSAROS, N. KATSAROSSearch for more papers by this authorE. VRACHNOU-ASTRA, E. VRACHNOU-ASTRASearch for more papers by this authorD. KATAKIS, D. KATAKISSearch for more papers by this author J. KONSTANTATOS, J. KONSTANTATOSSearch for more papers by this authorN. KATSAROS, N. KATSAROSSearch for more papers by this authorE. VRACHNOU-ASTRA, E. VRACHNOU-ASTRASearch for more papers by this authorD. KATAKIS, D. KATAKISSearch for more papers by this author First published: August 22, 1978 https://doi.org/10.1002/chin.197834121AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume9, Issue34August 22, 1978 RelatedInformation

Reduction of .alpha.-keto acids by low-valent metal ions. 1. Reaction of aqueous chromous ion with pyruvic acid

Reduction of .alpha.-keto acids by low-valent metal ions. 1. Reaction of aqueous chromous ion with pyruvic acid

Conversion of oxyhemoglobin to methemoglobin by organic and inorganic reductants.

Human oxyhemoglobin is converted to methemoglobin by a wide array of organic and inorganic reductants. Depending upon the concentration and nature of the reductant, varying amounts of deoxyhemoglobin are produced. The general overall sequence is: FeO2 leads to (1) FeIII leads to (2) FeII. The intermediacy of methemoglobin can be demonstrated by direct spectral observation and by cyanide trapping. For organic reductants, the second-order rate constants for (1) vary from greater than 300 (phenylhydroxylamine) to 1.4 X 10(-4) M-1 s-1 (malononitrile). Generally the rates parallel the ease of hydrogen abstraction by iron-bound oxygen from the substrate, and simply hydrocarbons are reactive. Rates for these processes have been ascertained with recrystallized protein, lysed cells, and intact human erythrocytes. At room temperature oxyhemoglobin quantitatively converts benzaldehyde to benzoic acid and hydroquinone to benzoquinone. Rates for inorganic species (process 1) range from greater than 7 X 10(3) (chromous ion) to 0.015 M-1 s-1 (ferrocyanide). Ferrous ion rapidly deoxygenates oxyhemoglobin by direct attack on the oxy complex but methemoglobin is not an intermediate with this reagent. Taken together the results support the theoretical prediction that reductants should oxidize oxyhemoglobin, and they demonstrate at least some degree of radical character to the oxy complex.

Chromous ion reduction of mammalian cytochrome oxidase and some of its derivatives

The reduction of cytochrome c oxidase by Cr2+, followed by means of stopped-flow spectrophotometry, exhibits two phases: the faster Cr2+-concentration-dependent reaction has an initial rate constant of 1.1 X 10(4)M-1-S-1, but reaches a rate limit at high concentration of reductant; the slower phase is concentration-independent with a rate of 0.3S-1. The activation energies of the fast and the slow processes are 35 and 71 kJ/mol respectively. The reduction kinetics of the mixed-valence CO complex and the cyanide-inhibited enzyme were compared with those of the fully oxidized forms: both the liganded species have a fast phase identical with that found in the oxidized oxidase. A comparison of the kinetic difference spectra obtained for the fast phase of reduction of oxidized oxidase with those obtained on reduction of the liganded species suggests that the rapid phase arises from the reduction ofhaem a, and the slow phase from the reduction of haem a3.

Stabilities of trivalent carbon species. 3. Reduction of organic cations by chromous ion

Stabilities of trivalent carbon species. 3. Reduction of organic cations by chromous ion

Dynamic Jahn-Teller effect for the chromous ion in KMgF3

The dynamic Jahn-Teller effect for the chromous ion in KMg${\mathrm{F}}_{3}$ is characterized by acoustic measurements. Acoustic-relaxation measurements and the temperature dependence of the acoustic-paramagnetic-resonance spectra are used in conjunction with theoretical vibronic levels of a molecular-cluster approximation to evaluate the tunnel splitting ($\ensuremath{\delta}=10$ ${\mathrm{cm}}^{\ensuremath{-}1}$) and spin-orbit splitting ($D=1.2$ ${\mathrm{cm}}^{\ensuremath{-}1}$). These values ($\ensuremath{\delta}, D$) are approximately one half those observed for MgO:${\mathrm{Cr}}^{2+}$ where the octahedral coordination of the chromous ion is with oxygen anions compared to fluorine anions in KMg${\mathrm{F}}_{3}$. The gyromagnetic ratio as well as the internal strains are estimated to be less in KMg${\mathrm{F}}_{3}$ than in MgO.

Dynamic Jahn-Teller effect forCr2+in MgO: Acoustic paramagnetic resonance

An empirical evaluation of the parameters defining the dynamic Jahn-Teller effect for ${\mathrm{Cr}}^{2+}$ in MgO is made using the temperature dependence of the acoustic-paramagnetic-resonance (APR) spectra. The molecular-cluster model for the tightly bound ${\mathrm{Cr}}^{2+}$ and its nearest neighbours is applied to the experimental results to determine the tunneling splitting and spin-orbit splitting. The magnitude of the tunneling splitting ($\ensuremath{\delta}\ensuremath{\sim}19$ ${\mathrm{cm}}^{\ensuremath{-}1}$) and spin-orbit splitting ($D\ensuremath{\sim}2.3$ ${\mathrm{cm}}^{\ensuremath{-}1}$) indicates the ${\mathrm{Cr}}^{2+}$ impurity is in a more extreme dynamic limit of the Jahn-Teller effect than previously assumed ($\frac{\ensuremath{\delta}}{D}\ensuremath{\sim}8$). The gyromagnetic ratio for the paramagnetic triplet levels of ${\mathrm{Cr}}^{2+}$ ions exhibits a significant anisotropy resulting from local distortions of the cubic site due to internal strains. The anisotropy depends on the acoustic mode used to observe the spectra. For longitudinal waves the observed anisotropy of the $g$ factor can be explained as due to induced transitions in ions in a primarily tetragonal environment. The magnitude of the internal strain is found to be approximately ${10}^{\ensuremath{-}5}$. Only doublet transitions are observed for the triplet even though the strain splitting (singlet-doublet) is found to be approximately 0.2 ${\mathrm{cm}}^{\ensuremath{-}1}$ which would allow $\ensuremath{\Delta}m=1$ transitions for the acoustic frequencies used in this investigation. The slow transverse mode couples more strongly to the chromous ion and exhibits an APR spectrum which is more complex than the longitudinal wave under similar conditions. The anisotropy of the $g$ factor is due to the same sets of ions as the longitudinal mode but the magnitude of the APR peaks depends on the direction of the magnetic field in the crystal.

The one-electron reduction of carbonium ions. X. Conformational effects of cyclopropyl group on the rate of one-electron reduction of cyclopropyltropylium ion with chromous ion

The one-electron reduction of carbonium ions. X. Conformational effects of cyclopropyl group on the rate of one-electron reduction of cyclopropyltropylium ion with chromous ion

Kinetic studies on mammalian cytochrome c modified with 2-hydroxy-5-hydroxy-5-nitrobenzyl bromide

The reduction of 2-hydroxy-5-nitrobenzyl tryptophyl cytochrome c by the chromous ion was studied by stopped-flow techniques. At pH6.5 the reduction of 2-hydroxy-5-nitrobenzyl tryptophyl cytochrome c is complex, showing the presence of three distinct phases. Two chromium concentration-dependent phases are observed (1.1 X 10(5) M-1-S-1, phase 1; 1.25 X 10(4)M-1-S-1, phase 2) and one slow first-order process (0.25S-1, phase 3). A comparison of the static and kinetic difference spectra, along with the data from the reduction of the reoxidized reduced protein, suggests that the slow chromium concentration-independent phase is due to a slow conformational event after fast reduction of the NO2 group. The rates of the chromium concentration-dependent phases show a marked variation with pH above 7.5. The activation energies for the three processes were also measured at 33.2, 38.6 and 69.7 kJ-mol-1 for phases 1, 2 and 3 respectively. The reaction of reduced 2-hydroxy-5-nitrobenzyl tryptophyl cytochrome c with CO was foollowed by means of both stopped-flow and flash photolysis. The combination with CO at pH 6.8 as measured in stopped-flow experiments showed two phases, one CO-dependent phase (phase 2, 2.4 X 10(2)M-1-S-1) and one CO-independent phase (phase 1, 0.015S-1). Investigation of the pH-dependence of the phases showed both the rates and amounts of each phase to be pH-invariant. CO recombination, after photolytic removal, was found to be biphasic; a CO-dependent phase (phase 2, 2.4 X 10(2)M-1-S-1) and a CO-independent phase (phase 1, 1.0s-1) were observed. A tentative model which can accommodate these observations is proposed.

Short Communications. A comparative study of some kinetic and spectral properties of guanidinated and native cytochrome c

An investigation of the spectral and some kinetic properties of a chemically modified cytochrome c is presented. The kinetics of reduction by chromous ion and ascorbate are shown to be unchanged from that of the native molecule, as are the kinetics of NO binding. The effects of pH on the visible spectrum are discussed in terms of a possible change in the pattern of co-ordination of the molecule with changing pH.