Abstract: A doubly N-confused porphyrin (N2CP), 2-ethoxy-5,10,15,20-tetrapentafluorophenyl-3,7-diaza-21,22-dicarbaporphyrin, and its Ag(III) and Cu(III) complexes were synthesized for the first time, via an acid-catalyzed condensation of pentafluorobenzaldehyde and meso-pentafluorophenyl-2,3‘-dipyrromethane. 1H NMR and single-crystal X-ray diffraction analyses reveal the arrangement of the three hydrogens (two CH and one NH) in the core of N2CP both in solution and in the solid state, respectively. The diamagnetic silver(III) complex has a square-planar tetracoordination and short Ag(III)−C bond distances of 1.987(8) and 2.011(8) A. Similarly, the diamagnetic Cu(III) complex shows a square-planar coordination with Cu(III)−C bond distances of 1.939(3) and 1.934(4) A. The trianionic nature of the N2CP ligand and a possibility of stabilizing the higher oxidation state by “confusion” are discussed.

Abstract: We have performed an in situ X-ray absorption spectroscopy (XAS) study to investigate the evolution of the local electronic and atomic structure of a high-surface-area Li 1-x Ni 0.85 Co 0.15 O 2 (0 ≤ x ≤ 1) cathode material during electrochemical delithiation. We have measured the changes in the oxidation state, bond distance, coordination number, and local disorder of Ni and Co absorbers as a function of the state of charge of the material. The X-ray absorption near edge spectra shows that delithiation of Li 1-x Ni 0.85 Co 0.15 O 2 leads to the oxidation of Ni 3+ to Ni 4+ . Ni atoms oxidize during the initial stages of charge and attain a maximum oxidation state of Ni 4+ well before the end of charge (x 0.85). On the other hand, Co atoms do not oxidize during the initial stages of charge but oxidize close to the end of charge. Analysis of the extended X-ray absorption fine structure (EXAFS) shows that the oxidation of Ni 3+ to Ni 4+ leads to the expected reduction in the Jahn-Teller effect. Also, to within the accuracy of the EXAFS technique, Co absorbers occupy Ni-type sites in the NiO 2 slabs. Furthermore, Co doping has a strong effect on the overall structural evolution and leads to a slight expansion of the a and b axes close to the end of charge.

Abstract: The reactivity of arsenopyrite (FeAsS) fractured surfaces toward oxygen was studied using synchrotron radiation excited photoelectron spectroscopy (SXPS). The spectra of the pristine surface provide evidence of different As and S surface sites. Signals for As3d with 0.33 eV lower and 0.37 eV higher binding energy than the bulk signal are attributed to arsenic surface sites with filled and unfilled dangling bonds, respectively, caused by the rupture of Fe-As and As-S bonds. Sulfur surface sites with filled dangling bonds, bonded to three iron as well as to two iron and one arsenic atom, give rise to a composite signal in the S2p spectra shifted by 0.79 eV to lower binding energy. Reaction of oxygen with FeAsS surfaces in ultra-high vacuum reveals fast oxidation of As surface sites with filled dangling bonds to As species of increasing oxidation state. The detection of oxidation states As 0 , As 2+ , As 3+ , and As 5+ indicate a consecutive reaction scheme for arsenic oxidation involving elementary one-electron transfer steps. The Fe3p spectra have a corresponding intensity increase of a component with a binding energy 1.1 eV higher than the Fe3p signal emitted from the pristine surface. This signal is assigned to Fe bonded to oxidized arsenic. The very small changes in the S2p spectra together with their decreased intensity indicate the formation of an arsenic and iron containing overlayer of oxidation products on top of the FeAsS mineral surface where the S2p signal arises from. In air oxidation of arsenic continues with As 5+ being the final oxidation product. An additional Fe3p signal at 56.1 eV binding energy is attributed to Fe bonded to O atoms formed during Fe oxidation. Sulfur oxidation leads to numerous intermediate oxidation products with sulfate being the final product. During air oxidation of up to 30 min, the sulfur signal at the low binding energy side of the S2p spectrum is broadened which is probably caused by S 2− formed in layers underneath As and Fe oxidation products. These oxidation products reach the surface by diffusion from the bulk (reaction induced segregation). A model of homogeneous oxidized layers on arsenopyrite indicates that reaction with air has produced a layer containing iron bonded to oxygen on top of the increasingly oxidized arsenic and iron containing layer. The Fe-O overlayer is about 1.8 monolayers thick and is probably formed through interaction of water with iron surface sites.

Abstract: The highly ordered mesoporous material HISiO2 was prepared at room temperature and low pH utilizing a high concentration of nonionic surfactant to achieve a hexagonal ordered phase with a pore size of ∼3.5 nm. The grafted amino ligand was covalently bonded to the internal pore surface of HISiO2 through a silanation procedure. Thereby, immobilized transition-metal−aquo complexes such as MnII-aquo (I), CuII-aquo (II), CoII-aquo (III), and ZnII-aquo (IV) were coordinated to the supported wall without impregnation on the surface. Diffuse reflectance spectroscopy (DRS) and electron paramagnetic resonance (EPR) studies observed that a proportion of the MnII complex was oxidized to a higher oxidation state, particularly MnIV. The kinetics and mechanism of redox reactions between o-aminophenol, o-phenylenediamine, and p-pheneylenediamine and the incorporated transition-metal−aquo−propylamine complexes have been investigated. The oxidation products of the amines have been monitored by UV−vis spectroscopy. The reac...

Abstract: The mechanism of catalytic oxidation reactions was studied using in situ X-ray absorption spectroscopy (XAFS) over a 17.5 wt% V2O5/Al2O3 catalyst, i.e., at reaction temperatures and in the presence of reactants. It was found that X-ray absorption near-edge structure (XANES) is a powerful tool to study changes in the local environment and the oxidation state of the vanadium centres during catalytic oxidation. At 623 K, the catalyst follows the associative mechanism in CO oxidation. XAFS revealed that the Mars–van Krevelen mechanism is operative at 723 K for CO oxidation. The extended X-ray absorption fine structure (EXAFS) results showed that the structure of the supported V2O5 phase consists of monomeric tetrahedral (Al–O)3–V=O units after dehydration in air at 623 K. However, the residuals of the EXAFS analysis indicate that an extra contribution has to be accounted for. This contribution probably consists of polymeric vanadate species. The structure remains unchanged during steady-state CO oxidation at 623 and 723 K. Furthermore, when oxygen was removed from the feed at 623 K, no changes in the spectra occurred. However, when oxygen is removed from the feed at 723 K, reduction of the vanadium species was observed, i.e., the vanadyl oxygen atom is removed. The V3+ ion subsequently migrates into the γ-Al2O3 lattice, where it is positioned at an Al3+ octahedral position. This migration process appears to be reversible; so the (Al–O)3–V=O units are thus restored by re-oxidation.

Abstract: A class of metallocene compounds is disclosed having general formula (I) wherein Y is a moiety of formula (II) wherein A, B, and D, same or different from each other, are selected from an element of the groups 14 to 16 of the Periodic Table of the Elements (new IUPAC version), with the exclusion of nitrogen and oxygen; R?1, R2, R3, R4 and R5? are hydrogen or hydrocarbon groups, Z is selected from a moiety of formula (II) as described above and from a moiety of formula (III) wherein R?6, R7, R8 and R9?, are hydrogen or hydrocarbon groups; L is a divalent bridging group; M is an atom of a transition metal selected from those belonging to group 3, 4, 5, 6 or to the lanthanide or actinide groups in the Periodic Table of the Elements (new IUPAC version), X, same or different, is hydrogen, a halogen, a R?10, OR10, OSO?2CF3, OCOR?10, SR10, NR10?2 or PR102 group, wherein the substituents R10 are hydrogen or alkyl groups; p is an integer of from 1 to 3, being equal to the oxidation state of the metal M minus 2. The above metallocenes are particularly useful in the polymerization of propylene.

Abstract: Reaction of the Mn4O4(6+) "cubane" core complex, Mn4O4L6 (1) (L = diphenylphosphinate, Ph2PO2-), with a hydrogen atom donor, phenothiazine (pzH), forms the dehydrated cluster Mn4O2L6 (2), which has lost two mu-oxo bridges by reduction to water (H2O). The formation of 2 was established by electrospray mass spectrometry, whereas FTIR spectroscopy confirmed the release of water molecules into solution during the reduction of 1. UV-vis and EPR spectroscopies established the stoichiometry and chemical form of the pzH product by showing the production of 4 equiv of the neutral pz radical. By contrast, the irreversible decomposition of 1 to individual Mn(II) ions occurs if the reduction is performed using electrons provided by various proton-lacking reductants, such as cobaltocene or electrochemical reduction. Thus, cubane 1 undergoes coupled four-electron/four-proton reduction with the release of two water molecules, a reaction formally analogous to the reverse sequence of the steps that occur during photosynthetic water oxidation leading to O2 evolution. 1H NMR of solutions of 2 reveal that all six of the phosphinate ligands exhibit paramagnetic broadening, due to coordination to Mn ions, and are magnetically equivalent. A symmetrical core structure is thus indicated. We hypothesize that this structure is produced by the dynamic averaging of phosphinato ligand coordination or exchange of mu-oxos between vacant mu-oxo sites. The paramagnetic 1H NMR of water molecules in solution shows that they are able to freely exchange with water molecules that are bound to the Mn ion(s) in 2, and this exchange can be inhibited by the addition of coordinating anions, such as chloride. Thus, 2 possesses open or labile coordination sites for water and anions, in contrast to solutions of 1, which reveal no evidence for water coordination. Complex 2 exhibits greater paramagnetism than that of 1, as seen by 1H NMR, and it possesses a broad (440 G wide) EPR absorption, centered at g = 2, that follows a Curie-Weiss temperature dependence (10-40 K) and is visible only at low temperatures, compared to EPR-silent 1. Its comparison to a spin-integration standard reveals that 2 contains 2 equiv of Mn(II), which is in agreement with the formal oxidation state of 2Mn(II)2Mn(III) that was derived from the titration. The EPR and NMR data for 2 are consistent with a loss of two of the intermanganese spin-exchange coupling pathways, versus 1, which results in two "wingtip" Mn(II) S = 5/2 spins that are essentially magnetically uncoupled from the diamagnetic Mn2O2 base. Bond-enthalpy data, which show that O2 evolution via the reaction 1-->2 + O2, is strongly favored thermodynamically but is not observed in the ground state due to an activation barrier, are included. This activation barrier is hypothesized to arise, in part, from the constraining effect of the facially bridging phosphinate ligands.

Abstract: A simple method for calculating the oxidation state of Cr in complexes containing only Cr−O bonds is presented. A total of 242 CrOn fragments with n = 3−6 were retrieved from the Cambridge Structural Database (CSD) and, together with the data for K3CrO8, were analyzed using the bond valence sum method. New R0 values for Cr(II) of 1.739(21) A, Cr(III) of 1.708(7) A, Cr(V) of 1.762(14) A, and Cr(VI) of 1.793(7) A were derived. An average R0 value of 1.724 A for Cr−O reproduces the oxidation state of 96 of the 110 Cr(II), Cr(III), and Cr(IV) CrOn complexes (n = 3−6) and that of K3CrO8 within 0.30 valence units. The crystal structure of K3CrO8 was redetermined at 173 K to provide accurate data for a Cr complex with both high oxidation state and coordination number. Potassium tetraperoxochromate(V), K3CrO8, is tetragonal, Space group Ī42m, a = b = 6.6940(3) A, c = 7.7536(5) A, Z = 2. The difficulties with fitting the observed valence for Cr(V) and Cr(VI) complexes with coordination numbers 4 and 5 are discusse...

Abstract: Tetrakis[bis(trimethylsilyl)methyl]digallane(4) 1 containing gallium atoms in an oxidation state of +II and a Ga–Ga single bond is a versatile starting compound for the synthesis of a broad variety of derivatives. One of the most exciting reactions is the substitution of alkyl groups without cleavage of the Ga–Ga bond, which succeeds by the treatment of 1 with chelating protonic acids such as carboxylic acids and acetylacetone derivatives. In all cases, two chelating ligands were introduced, which depending on their structural parameters either occupy terminal positions with each one co-ordinated to only one gallium atom or bridge the Ga–Ga bond. The reason for the different co-ordination behavior is discussed here.

Abstract: The oxidation state of polyaniline (PANI) can be varied from the fully reduced leucoemeraldine base (LEB) to the half oxidized emeraldine base (EB) and to the fully oxidized form pernigraniline base (PNB). In this work, the synthesis and properties of the highest oxidation state of polyaniline, pernigraniline, in the base as well as the corresponding salt form are discussed.

Abstract: The reactions of oligomeric niobium oxide anions (up to Nb 6 O 15 − ), generated by laser ablation and studied using a Fourier transform ICR mass spectrometer, have been used to deduce the roles of (i) Nb(III,IV,V) centers, (ii) Nb/O double bonds and (iii) proximal Nb centers, in the catalytic activation of methanol and ethanol. The most important recurring mechanism involves initial alcohol condensation at a cluster metal-oxygen double bond to yield Nb(OH)(OCH 3 ). There is no change in the oxidation state of the cluster during this step. The so-formed niobium-hydroxyl bond is the new reactive site in the cluster, and undergoes ligand switching in a follow-up collision to yield a bis-methoxy cluster and neutral water. Dehydrogenation is only observed to occur with clusters possessing two Nb/O double bonds at a single metal center, and involves reduction of the participating Nb(V) center to Nb(III). An ion ejection/selection step was used to monitor the activity of a number of the ionic reaction products towards the alcohols, and in most instances spontaneous or kinetically-activated decomposition resulted in regeneration of the parent cluster from the substituted species.

Abstract: The article contains sections titled: 1. Introduction 2. Mineralogy, Abundance, Occurrence 3. Properties 3.1. Properties of the Nuclei 3.2. Properties of the Atoms and Ions 3.2.1. Electronic Configuration, Position in the Periodic Table 3.2.2. Oxidation States, Atomic and Ionic Radii 3.2.3. Magnetic and Spectral Properties 3.2.4. Bonding, Coordination Numbers 3.3. Other Chemical and Physical Properties 3.4. Miscibility and Alloying Behavior 3.5. Mechanical Workability 4. Digestion of Rare Earth Ores 4.1. Wet Chemical Digestion; Fusion 4.1.1. Monazite 4.1.2. Bastnaesite 4.1.3. Other Ores 4.2. Direct Chlorination at High Temperature 5. Separation 5.1. Principles of Separation 5.2. Separation by Classical Methods 5.2.1. Fractional Crystallization 5.2.2. Fractional Precipitation 5.2.3. Separations Based on Oxidation State Changes 5.3. Separation by Ion Exchange 5.3.1. Ion Exchange with Chelating Agents 5.3.2. Separation Process 5.3.3. Industrial Processes 5.3.4. Disadvantages of Ion Exchange 5.4. Separation by Liquid - Liquid Extraction 5.4.1. Theoretical Basis 5.4.2. Extractants 5.4.2.1. Neutral Extractants 5.4.2.2. Acidic Extractants 5.4.2.3. Amines and Quaternary Ammonium Salts as Extractants 5.4.2.4. Synergistic Effects 5.4.3. Industrial Liquid - Liquid Extraction 5.4.3.1. Separation of Europium Oxide 5.4.3.2. Separation of Yttrium Oxide 5.4.3.3. Separation of Scandium 6. Production of the Metals 6.1. Fused Salt Electrolysis 6.2. Metallothermic Reduction 6.3. Purification 7. Analysis 8. Compounds 8.1. Hydrides 8.2. Oxides, Hydroxides, Peroxides, Salts of Inorganic Oxoacids, Double Salts 8.3. Halides 8.4. Chalcogenides 8.5. Nitrides 8.6. Carbides 8.7. Complexes; Organic Compounds 9. Uses 10. Economic Aspects 11. Toxicology 12. Acknowledgement

Abstract: An in situ X-ray absorption spectroscopy (XAS) spectroelectrochemical study of aquocobalamin (system B12a-B12r-B12s) has been carried out in aqueous solutions buffered at different pH values. To the best of our knowledge, this is the first structural study of aquocobalamin at room temperature under controlled oxidation conditions. Most of the previous work was in fact performed using frozen samples chemically treated to produce the species. The spectroelectrochemical approach offers several advantages: (1) the reduction products may be studied without poisoning the system with chemical reductive reagents and (2) any possible variation of the oxidation state owing to the electrons produced by the incident beam is avoided as the electrode, under potentiostatic control, acts as a scavenger. The spectroelectrochemical approach, together with more careful data analysis, has led to an improved interpretation of the XAS data. These conditions were not met in previous works where the oxidation state was not controlled and multiple scattering contributions were not taken into account. The general shape of the XAS spectra of the different species is not greatly affected by pH. A signature for the base-off square-planar coordination has been evidenced for the Co(II) compound at basic pH. A new signature for Co(I), indicating square-planar coordination, has been identified on the experimental spectra and simulated in theoretical X-ray absorption near-edge structure (XANES) studies. The flexibility of the electrochemical approach, that permits to unambiguously establish the formal oxidation state, has led to very reliable values for energy shift and peak intensity variations. The experimental XANES and extended X-ray absorption fine structure (EXAFS) spectra with a very good signal-to-noise ratio have been processed using the GNXAS package that takes into account multiple scattering contributions. EXAFS and XANES independent analysis result in the same structural model. The reduction from Co(III) to Co(II) produces the most significant structural changes: the cobalt coordination number decreases from six to five, and the edge position shifts by 2.4±0.3 eV. In addition, the XANES spectra are strongly modified. The reduction from Co(II) to Co(I) produces mainly electronic effects with no apparent change of the coordination number. A discussion of the limits and potentialities of EXAFS in this type of study has also been included.

Abstract: CuOx-modified and unmodified Mn2O3, Cr2O3 and WO3 catalysts were prepared by impregnation with Cu(NO3)2 solution and/or calcination at 700°C of appropriate precursor compounds. Bulk phase composition and thermochemical stability were characterized by X-ray diffractometry, infrared spectroscopy and thermogravimetry. The surface area, chemical composition, oxidation state and chemisorption capacity were determined by X-ray photoelectron spectroscopy and sorptometry of N2, O2 and CO gas molecules. The catalytic CO oxidation activity was tested, using a gas circulating system equipped with a fixed-bed microreactor and a gas chromatograph. The CuOx additives were found to promote markedly the otherwise insignificant CO oxidation activity of WO3 at 250–400°C. This was related to concomitant improvement primarily in the lattice oxygen reactivity, and in the O2 chemisorption capacity. The already high CO oxidation activities of Mn2O3 and Cr2O3 catalysts at 150–250°C were found to be, respectively, slightly and hardly improved by CuOx additives, despite a marked improvement in oxygen chemisorption capacity. This was attributed to establishment on the unmodified catalysts of a favourable electron-mobile environment. In oxygen-rich reaction atmosphere, both the modified and unmodified catalysts were thermochemically stable. However, in lean oxygen atmosphere, Cr2O3 and CuOx-modified WO3 were relatively the most stable test catalysts.

Abstract: The roles of the different sites and structures of supported vanadium oxide catalysts have been studied by in situ spectroscopic techniques (UV-Vis-DRS and Raman) as well as by the use of isotopic oxygen labeling, in order to propose a molecular understanding of the roles of the different oxygen sites The remarkable effect of the different oxide supports on the activity per vanadium site (TOF) underlines the relevance of the bridging V-O-support bond as the active site The reducibility of the support appears to correlated with the activity per vanadium site In situ Raman studies employing isotopic oxygen labeling rule out the terminal V=O bond as the critical site involved in the rate determining step for the oxidation of ethane The bridging V-O-V bonds appear to have a moderate participation and the bridging V-O-Support bonds appear to be the critical site for ethane oxidation In situ UV-Vis-DRS and in situ Raman spectroscopy are complementary for the determination of the polymerization degree of the surface vanadium oxide species Under reducing conditions, polymeric surface vanadia species are more reducible than isolated species and vanadia supported on reducible oxides (titania, zirconia, ceria) is more reducible than vanadia supported on less reducible oxides (silica, alumina) However, the oxidation state under reaction conditions does not depend on the reducibility of the surface vanadia species, but on the average oxidation state under steady-state oxidation of ethane

Abstract: Copper is classed as a transition metal both from its physico-chemical properties and its biochemical behavior. This review includes thirty formally copper(III) compounds where crystal structure has been determined. Coordination number four dominates with mostly a square-planar arrangement about the copper(III) atom. Sulfur donor ligands by far prevail. In general the Cu-L bond distance elongated with a decreased oxidation state of copper in the sequence: Cu(III)-L > Cu(II)-L > Cu(I)-L. Examples of distortion isomerism exist.

Abstract: We present the synthesis of a hybrid material containing fluorinated iron porphyrins through hydrolysis and polycondensation of iron porphyrin bearing a trifluorosilyl function with tetraethoxysilane in the presence of nitrogen bases acting as template molecules. The presence of metalloporphyrin Soret band is detected in the ultraviolet–visible absorption spectra of all metalloporphyrinosilica-templates. Thermogravimetric analysis and electron paramagnetic resonance of the materials also confirm the presence of metalloporphyrin in a silica network. Electron spectroscopy imaging was that of a non-crystalline microstructure. The iron and silicon distribution are homogeneous for the elements in all particle sites. The iron porphyrinosilicas-template were active as catalysts for cyclooctene epoxidation using iodozylbenzene as oxygen donor. In general, the epoxidation yield is larger for iron porphyrinosilicas-template than for manganese porphyrinosilicas-template. The manganese porphyrinosilicas-template had a smaller activity due to their manganese oxidation state. The largest catalytic yield were obtained with the iron porphyrinosilica-pyridine (85%).

Abstract: We present here experimental results that investigate the effects of metal−ion binding on iron−ion sorption to and recovery from alfalfa biomass. Fe(II)− and Fe(III)−ion binding were measured in order to ascertain the differences in binding strengths due to changes in oxidation state. Stronger binding was found for iron(III)−biomass as compared to iron(II)−biomass. The optimal pH for iron uptake was determined to be 5. The results of pH binding profile, iron desorption, and temperature-dependent binding experiments as well as X-ray spectroscopic (XAS) measurements all suggest that binding of iron by alfalfa biomass may be occurring through carboxyl ligands. The XAS experiments further demonstrate that the metal binding proceeds without an oxidation state change, and both iron(II) and iron(III) have similar coordination environments. The information presented will assist in understanding the binding of other metals to alfalfa biomass and in developing methods for their recovery.

Abstract: The oxidation state and the structural properties of Al2O3-supported bimetallic PdCu catalysts during the catalytic reduction of KNO3 carried out in the aqueous phase were investigated by X-ray absorption spectroscopy. Under reaction conditions the noble metal component (Pd) was in a reduced state, while the less noble metal (Cu) was found to be partially oxidized. A PdCu phase was formed in the bimetallic catalysts, which appears to be located in small domains on the surface of Pd rich particles.

Abstract: The Ge-Li bond in 1 reacts readily with water and oxygen to give 2 (Li/H exchange) and 3 (insertion), respectively. In both cases the partial charge and the oxidation state of the germanium atom changes. All compounds were characterized by X-ray crystallography.

Abstract: Adsorption of NO on vanadia–titania samples pre-subjected to different reduction treatments has been studied by FTIR spectroscopy. When the NO adsorption is performed at 85 K on oxidized samples, antisymmetric NONO species, typical for V5+ sites, are detected and characterized by bands at 1779 and 1686 cm−1. At ambient temperature, however, adsorption is negligible and only with time reactive adsorption occurs producing NO+ (2120 cm−1), nitro/nitrato species (bands in the 1650–1100 cm−1 region) and weakly adsorbed NO (broad band at 1915 cm−1). Adsorption of NO at ambient temperature on reduced samples results in the formation of two types of species: (i) V4+(NO)2 dinitrosyls characterized by νs(NO) and νas(NO) at 1903–1880 and 1769–1753 cm−1, respectively, and (ii) V3+(NO)2 complexes, which give rise to νs(NO) at 1834–1822 cm−1 and νas(NO) at 1697–1685 cm−1. At low temperature the dinitrosyls are transformed into species in which more than one (NO)2 dimer is attached to one cationic site. Addition of O2 to NO, preadsorbed on reduced vanadia–titania samples, results in a fast oxidation of the V3+(NO)2 species, whereas the V4+(NO)2 complexes are more stable and do not disappear completely in the presence of oxygen. The results obtained suggest that NO is a convenient probe molecule for the analysis of the oxidation state of vanadium in vanadia–titania catalysts. To prevent oxidation of reduced vanadium sites, low equilibrium pressures of NO and registration of the IR spectrum soon after the NO admission are recommended.

Abstract: Measurements of redox equilibria involving a number of transition metals (Fe, Mn, Ti, and V) are summarized and discussed with respect to the effects of oxygen activity and chemistry of the melts on the oxidation state of the transition metal oxide. Recently measured data on kinetics of CO-CO2 on surfaces of calcium silicate-based slags containing 1 to 68 wt pct FeO x or 18 to 38 wt pct MnO x are presented and discussed in terms of the limiting steps and the dependence of the limiting step on concentration of the transition metal oxides in the melts. Similar data on nonferrous-type slags containing PbO, ZnO, or TiO x in the presence or absence of FeO x are also reviewed. The review also includes recent investigations of the effects of iron oxide on the diffusivity of iron and oxygen in slags.