Showing papers on "Chromium published in 1982"
TL;DR: In this paper, the authors present a Web of Science Record created on 2006-02-21, modified on 2017-05-12, with the purpose of improving the quality of the record.
Abstract: Reference LPI-ARTICLE-1982-004doi:10.1021/ja00375a010View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
563 citations
TL;DR: The corrosion rates of chromium and nickel showed a slight increase, while cobalt and copper dissolved to a very much greater extent in the presence of protein, however, with molybdenum the corrosion was inhibited by protein.
Abstract: The corrosion of the pure metals aluminium, cobalt, copper, chromium, molybdenum, nickel, and titanium and of a cobalt-chromium molybdenum casting alloy has been studied in buffered saline with and without the presence of the proteins serum albumin and fibrinogen. The corrosion of aluminium and titanium was unaffected by the protein. The corrosion rates of chromium and nickel showed a slight increase, while cobalt and copper dissolved to a very much greater extent in the presence of protein. However, with molybdenum the corrosion was inhibited by protein.
238 citations
TL;DR: In this paper, NaxCrO2 and NaxNiO2 were obtained for the first time by electrochemical desintercalation from NaCrO 2 and NaNiO 2.
191 citations
163 citations
TL;DR: A low valent chromium reagent is generated from chromium(III) chloride and a half mol of lithium aluminum hydride in tetrahydrofuran as mentioned in this paper, which behaves similarly to anhydrous chromium (II) chloride, which is commercially available, and reduces allylic halides to produce unisolable allylchromium species which add efficiently to aldehydes or ketones with high degree of stereo and chemoselectivity.
Abstract: A low valent chromium reagent is generated from chromium(III) chloride and a half mol of lithium aluminum hydride in tetrahydrofuran. The reagent behaves similarly to anhydrous chromium(II) chloride, which is commercially available, and reduces allylic halides to produce unisolable allylchromium species which add efficiently to aldehydes or ketones with high degree of stereo- and chemoselectivity. Particularly, high threo selectivity is observed in the reaction of aldehydes and 1-bromo-2-butene and is ascribed to a chair-like six-membered transition state. Simple reduction of allylic and benzylic halides produces biallyls and bibenzyls, while gem-dibromocyclopropanes afford the corresponding allenes in excellent yields.
142 citations
TL;DR: In this article, the interaction of the natural marine polymer chitin and its deacetylated derivative chitosan with chromium has been investigated using atomic absorption spectroscopy.
Abstract: The interaction of the natural marine polymer chitin and its deacetylated derivative chitosan with chromium has been investigated. The uptake of chromium from aqueous solution was determined from changes in concentration as measured by atomic absorption spectroscopy. The uptake of Cr(III) on chitosan was significantly greater than that on chitin. The smaller the size fraction of the chitin/chitosan, the greater the uptake of Cr(III). The Cr(III) uptake increased with increasing solution pH. Minimal desorption of chromium was observed on washing previously chromium-equilibrated chitosan with distilled water. The uptake of Cr(III) by chitosan was enhanced in the presence of phosphate, whereas the converse was not observed. Minimal uptake of Cr(VI) as dichromate by chitin and chitosan was measured. Cr-containing nodules were noted in the SEM/EDAX analysis for Cr(III)-equilibrated chitosan. Cr-containing clusters were detected for Cr(III)- plus phosphate-equilibrated chitosan. XPS results supported the conclusions drawn from the isotherm studies.
113 citations
106 citations
Patent•
27 Sep 1982TL;DR: In this paper, a novel catalyst was proposed for 3,3,3-trifluoropropene by the reaction of hydrogen fluoride gas with a halogenated hydrocarbon.
Abstract: A catalyst composition useful in preparing 3,3,3-trifluoropropene by the reaction of hydrogen fluoride gas with a halogenated hydrocarbon is provided. A novel catalyst is prepared by simultaneous fluorination of chromium and aluminum oxides. This or conventional chromium oxyfluoride compounds may additionally be activated by contact with chlorine or pentachloroethane. A process for the preparation of 3,3,3-trifluoropropene is also contemplated.
102 citations
97 citations
92 citations
TL;DR: In this paper, it was concluded that the mode of outward chromium transport gradually changes during the high vacuum treatment: from lattice and grain-boundary diffusion and possibly vapor transport along microcracks during the initial stage to lattice diffusion only for the densified scales.
Abstract: Cr specimens preoxidized at 1100–1300°C to give Cr2O3 scales with varying thicknesses and microstructures have been treated at temperature in high vacuum. During the high vacuum treatment the specimens lose weight due to outward Cr transport through the Cr2O3 scales. The initial rate of weight loss gradually diminishes, but eventually the weight loss reaches a linear rate. Concurrently the Cr2O3 scale exhibits grain growth and densifies. It is concluded that the mode of outward chromium transport gradually changes during the high vacuum treatment: from lattice and grain-boundary diffusion and possibly vapor transport along microcracks during the initial stage to lattice diffusion only for the densified scales. It is concluded that chromium diffuses by an interstitial type mechanism. Self-diffusion coefficients of Cr in Cr2O3 at the Cr-Cr2O3 phase boundary have been calculated from the linear rates of chromium transport for different defect structure situations.
TL;DR: The stable form of dissolved chromium in oxygenated seawater is Cr(VI), but Cr(III)-species are also present at an analytically significant level.
TL;DR: In this article, the structure of a lamellar compound with S|Cu 0.33 Cr 0.50 PS 3 is modeled as a two-dimensional Heisenberg model, where copper is not located at the center of its octahedral sites but is distributed among a continuous series of positions within these sites.
TL;DR: Chromium(VI) [Cr(VI)] is adsorbed as HCrO − 4 on iron(III) hydroxide at pH below 8.5 as mentioned in this paper.
TL;DR: In this article, a number of spectrum lines of highly ionized copper, nickel, iron, chromium, and germanium have been observed and corresponding transitions identified and the transitions pertain to the ground configurations of the respective ions, which are the only states strongly populated at tokamak plasma conditions.
Abstract: A number of spectrum lines of highly ionized copper, nickel, iron, chromium, and germanium have been observed and the corresponding transitions identified The element under study is introduced into the discharge of the PLT Tokamak by means of rapid ablation by a laser pulse The ionization state is generally distinguishable from the time behavior of the emitted light New identifications of transitions are based on predicted wavelengths (from isoelectronic extrapolation and other data) and on approximate expected intensities All the transitions pertain to the ground configurations of the respective ions, which are the only states strongly populated at tokamak plasma conditions These lines are expected to be useful for spectroscopic plasma diagnostics in the 1-3 keV temperature range, and they provide direct measurement of intersystem energy separations from chromium through copper in the oxygen, nitrogen, and carbon isoelectronic sequences
TL;DR: In this article, the distortion of the 16-membered N6 tetradentate macrocyclic ligand is calculated in terms of DT/DQ by applying NSH theory.
Abstract: Trivalent chromium, manganese, iron and cobalt salts reactin situ with 2,6-diaminopyridine and acetylacetone to form complexes of the 16-membered N6 tetradentate macrocyclic ligand. The chelates are characterised as distorted square-pyramidal of [M(TML)X] type, where M = chromium(III), manganese(III), iron(III) and cobalt(III); X=Cl, Br, NO3 or NCS for chromium(III) and iron(III) and X=(OAc) for manganese(III) and (OH) for cobalt(III). The ligand coordinates through all the nitrogen atoms through deprotonation of two of them, however, the pyridine nitrogens do not take part in coordination. The chelates incorporate one anion or hydroxyl group in the coordination sphere. The magnetic, electronic and i.r. spectral studies indicate lower symmetries for these chelates. The amount of distortion is calculated in terms of DT/DQ by applying NSH theory. X-ray measurements on powder form of the complexes show their isomorphic nature and also support the proposed structures.
TL;DR: In this paper, it was shown that phosphorus is more electonegative with respect to chromium and manganese than to iron and that more charge is drawn from these atoms onto phosphorus.
TL;DR: The reaction of nicotinic acid (nic), chromic perchlorate hexahydrate, and sodium perchlorates in aqueous solution affords a Cr(III)-vitamin complex whose composition has been established to be Na[Cr3O(nicH)6(H 2O)3][ClO4]8·nicH·6H2O, based on analytical data and single-crystal X-ray analysis.
TL;DR: In this paper, a model for the formation of binary intermetallic compounds of Cr and Mn with arbitrary metal partners is presented, and the effect of the magnetic properties on the enthalpies of formation is discussed.
Abstract: As has been done in a previous paper [4] on alloys of Sc, Ti and V, we present in this paper model predictions for heats of formation of binary intermetallic compounds of Cr and Mn with arbitrary metal partners. Enthalpies of liquid alloys are also predicted. Calculated values are compared with experimental data as with the qualitative information that can be derived from the phase diagrams. The available binary phase diagrams based on Cr and Mn are presented. The effect of the magnetic properties on the enthalpies of formation is included in the discussion.
TL;DR: In this article, the minimum metal concentrations in the permeate from separate batches of chromium, nickel, copper and zinc rinsewaters were found to be, respectively, 0.17 mg 1 −1 Cr (T), 0.26 mg 1−1 Ni (Ni, Ni, Cu and Zn).
TL;DR: In this article, a study of the kinetics of formation and microstructure of aluminide coatings on Ni-Cr alloys has been made, where a parabolic growth rate law was observed for most of the runs, except for slight deviations in low activity packs run at low temperature.
TL;DR: In this article, secondary ion mass spectrometry was used to study post-annealing concentration profiles of Fe and Cr implants in undoped InP substrates, and the results were interpreted according to the calculations of L. A. Christel et al. on stoichiometric disturbances in ion-implanted compound semiconductors.
Abstract: The post‐annealing concentration profiles of Fe and Cr implants in undoped InP substrates are studied by secondary ion mass spectrometry. Annealing temperatures range from 550 to 750 °C. Iron and chromium show similar behavior; the profiles are divided in three regions: the near surface zone where metals pile up, the zone in front of the projected range (Rp), around 0.8 Rp, where Fe and Cr atoms are trapped by residual damage, and a region around Rp+ΔRp, where a well‐defined peak, with maximum concentration reaching 3–4×1018 cm−3, is observed. On each side of that peak, solute atoms are depleted down to the limit solubility: 1×1017 cm−3 for iron, 2×1016 cm−3 for chromium. The results are interpreted according to the calculations of L. A. Christel et al. [J. Appl. Phys. 52, 5050 (1981)] on stoichiometric disturbances in ion‐implanted compound semiconductors.
TL;DR: Results confirm the view that the active mutagenic agent in intact cell systems is Cr(VI), but indicate that industrial Cr(III) compounds cannot be considered genetically inert, as they can be contaminated by Cr( VI) and induce chromosomal aberrations.
Abstract: Ten Cr(III) compounds, used in the leather tanning industry, and a Cr(III) compound, containing chromite and used as a pigment, were tested for cytotoxicity (inhibition of growth and survival of cultured hamster cells), mutagenicity (point mutations in S typhimurium) and clastogenic activity (chromosomal aberrations and sister chromatid exchanges in hamster cells) Reference Cr compounds were potassium dichromate as Cr(VI), and chromium chloride and two different preparations of chromium nitrate as Cr(III) A contamination with Cr(VI) was detected in some of the Cr(III) tannins, chromite and one chromium nitrate Cr(III) compounds were cytotoxic at concentrations of Cr(III) 100-500 times higher than Cr(VI), but contaminated Cr(III) compounds showed a significant cytotoxicity Reference Cr(VI) but not Cr(III) was mutagenic: of the contaminated compounds only chromite and chromium nitrate, which contained higher levels of Cr(VI), were found to be mutagenic The frequency of sister chromatid exchanges was significantly increased only by Cr(VI) and the more contaminated Cr(III) compounds However, an increase of chromosomal aberrations was produced also by reference Cr(III) salts and the weakly contaminated industrial Cr(III) compounds These results confirm the view that the active mutagenic agent in intact cell systems is Cr(VI), but indicate that industrial Cr(III) compounds cannot be considered genetically inert, as they can be contaminated by Cr(VI) and induce chromosomal aberrations
TL;DR: The stereochemical outcome of chromium(II)-mediated syntheses of homoallylic alcohols has been examined on 11 aldehydes, 3a − 13a.
TL;DR: In this paper, the influence of cation distribution in tetrahedral and octahedral magnetites on the oxidation temperature was shown directly by differential thermogravimetric analysis and by electrical conductivity.