Low Concentrations Of Cobalt Research Articles

Nodular accumulation of type II cells and inflammatory lesions caused by inhalation of low cobalt concentrations

Eight rabbits were exposed to 2 mg/m3 and eight to 0.4 mg/m3 of cobalt as CoCl2 for 14-16 weeks (5 days/week, 6 hr/day). Eight rabbits were used as controls. Light microscopic examination of the lungs showed nodular accumulation of alveolar type II cells in all cobalt-exposed rabbits. Abnormal macrophage reaction was observed in all eight rabbits exposed to the high dose and in five of the eight exposed to the low dose. Interstitial inflammation was present in all the rabbits exposed to the high dose and in half of the rabbits exposed to the low dose. Ultrastructural morphometric examination revealed no significant increase in the volume density of type II cells in the cobalt-exposed animals, as the nodular accumulation of these cells was balanced by an increased number of interjacent fields devoid of type II cells. In cobalt-exposed lungs, there was focal swelling of both type I and type II cells, and some of the latter lacked microvilli. The effect pattern after CoCl2 exposure was thus clearly different from those patterns seen after exposure to other toxic metals. We speculate that nodular accumulation of type II cells represents the primary lesion in CoCl2-exposed lungs and that the proliferation of such cells in interjacent areas might be suppressed by a feedback mechanism regulating surfactant production in the terminal airspaces.

Liquid phase oxidation of p-xylene to p-toluic acid

The liquid phase oxidation of p-xylene to p-toluic acid by air in the presence of low concentrations of cobalt acetateȁsodium bromide (0.04 M) as a catalyst was investigated at temperatures between 333 and 378 K. Maximum p-toluic acid formation was obtained at a stoichiometric ratio of cobalt acetate to sodium bromide of 1:2.

Ecological studies in the paper mill effluents and their impact on the river Tungabhadra: Heavy metals and algae

Certain metals have been investigated in paper mills effluent channel and in the river Tungabhadra in relation to their distribution, seasonal fluctuations and their effect, if any, on algae. The concentrations of various metals analysed are in the order of Zn>Cu>Pb>Ni>Co>Mn. In general these metals indicated an increase in their concentration along with the increase in the concentrations of chlorides, total hardness, sulphates and total alkalinity. Blue-greens and diatoms seem to be more tolerant to these ions than Chlorophyceae.Stigeoclonium exhibited very good growth at high concentrations of zinc, copper and nickel and at low concentrations of cobalt and lead.Schizomeris attained good growth when the lead concentration was high and cobalt was low.

Search for thermometers with low magnetoresistive effects: platinum-cobalt alloy

Measurements performed on thermometers made of dilute ferromagnetic alloys of Pt with 0.45, 0.50, 0.75, 1.06 and 2.15 at% Co, in the temperature range 2–28 K and in magnetic fields up to 6 T showed a large region of negative magnetoresistivity that limits the magnetic error at low temperatures and field values. With 0.5 at% Co or less, the change of the magnetic error with T and B was smooth, while a magnetic transition has been observed with higher cobalt concentrations. Curie temperature has been found to occur at 6.0 K, 14.2 K and, by extrapolation, 32 K for alloys with 0.75, 1.06, and 2.15 at%Co respectively. The transition resulted in a second order discontinuity of the R-T characteristics at B = 0 and B = 3.8 ± 0.2 T with 0.75 at%Co and 8.0 ± 0.5 T with 1.06 at%Co, while for other field values the discontinuity was first-order. Hence, this alloy can be used for thermometry only with very low cobalt concentrations: with 0.3 at%Co it would be possible to limit the magnetic error within ±0.2 K up to 2 T and done to 5 K.

Cobalt mapping of the nervous system: how to avoid artifacts.

Infusion of cobalt ions into cut axons is an established method for tracing neuron projections in the central nervous system. Artifacts, where unintended neurons are stained, however, have been reported, leading to difficulties in interpretation. Experiments in the locust Schistocerca gregaria Forskål show that such artifacts can be induced through damage to axons caused by cutting peripheral nerves and by using high cobalt chloride concentrations (0.4M and above). Mixtures of cobalt and nickel chlorides and nickel chloride alone were introduced into different branches of the same nerve and developed with rubeanic acid to give precipitates of different colors in the two sets of axons. Preparations were examined with the light microscope, where mixing of ions would appear as intermediate colors, and by x-ray probe microanalysis. No evidence for leakage of metal ions from the filled axons or for ion uptake by other axons could be detected, provided that low concentrations of cobalt and nickel chlorides were used and nerve cutting was reduced to a minimum by making preparations in vivo. If extreme conditions are avoided when making the preparation, the risk of producing artifacts is minimized, thus enabling the cobalt method to be used with greater confidence for describing neuronal projections.

The influence of zinc on the surface properties of cobalt-alumina catalysts

Addition of a small quantity of zinc to γ-Al 2O 3 was studied with respect to influence on the surface properties of a series of Co Al 2O 3 catalysts. ESCA and ISS results indicate that at low cobalt concentrations (≤8% Co) the presence of zinc can enhance formation of a cobalt “surface spinel” resulting from the diffusion of Co ions into tetrahedral sites of the γ-Al 2O 3 support. At higher cobalt loadings a drastic increase in the ESCA and ISS metal/support intensity ratios is seen relative to catalysts without zinc. X-Ray diffraction data indicate that the increases in intensity ratios result from an increase in dispersion, i.e., generation of smaller cobalt oxide crystallites in the zinc-doped catalysts. For a series of catalysts having fixed cobalt concentrations, the influence of particle size on ESCA and ISS intensity ratios was determined.

Seed cobalt in Lupinus angustifolius

The concentration of cobalt in seeds of Lupinus angustifolius varied widely from 6 ng/g to 730 ng/g. High concentrations of cobalt were associated with high concentrations in cotyledons and embryo with much lower concentrations in the seed coat. The effect of the cobalt content of seeds on the response of two cultivars of L. angustifolius to cobalt application was examined in a glasshouse trial. Plants of the Unicrop cultivar grown from seed with a cobalt concentration of 730 ng/g did not respond to cobalt application. By contrast plants grown from seed with a much lower cobalt concentration (10 ng/g) responded markedly. In the Uniharvest cultivar increasing the seed cobalt concentration from 6 to 27 ng/g by cobalt application to the seed crop as a soil dressing did not reduce the extent of a very marked response to cobalt application.

X-ray photoelectron spectroscopic study of unsupported cobalt-molybdenum sulfide catalysts

X-Ray photoelectron spectroscopic (XPS) measurements have been made on unsupported, fully sulfided, cobalt-molybdenum catalysts which had previously operated catalytically until attainment of steady activity. Total sulfur content and intrinsic activity for hydrogenolysis of thiophene, for hydrogenation of cyclohexene and for isomerization of cyclohexane are also reported. The entire range of concentration 0.0 < r < 1.00, where r = Co (Co + Mo) , has been investigated. There exists a good correlation between XPS and catalytic activity measurements. Two concentration domains can be distinguished. In the low cobalt concentration range there is an increase in the binding energy of the Mo 3d 5 2 , Mo 3d 5 2 , and S 2p 3 2 − 1 2 levels. In the range of concentration where the catalysts exhibit a strong synergy for hydrogenolysis and isomerization, the binding energy of these levels decreases. Furthermore, the sulfur content is maximum. The formation of a reduced species with a charge between Mo 4+ and Mo 3+, which could be involved in the active sites, has been postulated.

Solvent extraction with di(2-ethylhexyl)phosphoric acid; A correlation between selectivity and the structure of the complex

Distribution coefficients for a number of divalent transition metal ions and for iron (III) between aqueous phases of constant ionic strength and an organic phase containing 30% sodium di-(2-ethylhexyl)phosphate (D2ENa) have been measured with variable temperature. Three distinct types of extraction have been observed and have been correlated with the structures of the complexes and the predictions of ligand field theory. For cobalt(II) a 6-coordinate derivative Co(D2E) 2(H 2O) 2 has been postulated to explain the thermochromism observed in the cobalt extraction at low cobalt concentrations. This reaction has been studied at temperatures between 20°C and 100°C and values of 48·3 kJ mol −1 and 148 J mol −1°C −1 for ΔH and ΔS respectively have been estimated for the octahedral → tetrahedral conversion. The importance of the entropy effect for the extraction of manganese(II), iron(II) and cobalt(II) is stressed.

Determination of low concentrations of cobalt in small samples of plant material by flameless atomic absorption spectrophotometry

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDetermination of low concentrations of cobalt in small samples of plant material by flameless atomic absorption spectrophotometryW. J. SimmonsCite this: Anal. Chem. 1975, 47, 12, 2015–2018Publication Date (Print):October 1, 1975Publication History Published online1 May 2002Published inissue 1 October 1975https://doi.org/10.1021/ac60362a013RIGHTS & PERMISSIONSArticle Views53Altmetric-Citations25LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Determination of low concentrations of cobalt in plant material by atomic absorption spectrophotometry.

Determination of low concentrations of cobalt in plant material by atomic absorption spectrophotometry.

The chemical diffusion coefficient in dilute copper-cobalt alloys

The chemical diffusion coefficient in dilute copper-cobalt alloys has been determined as a function of composition in the temperature range 800–1073°C. Diffusion couples were made from pure copper and pure cobalt cylinders, and concentration vs. distance curves in the α phase were determined by microprobe analysis. A modified form of the method introduced by Hall was used to analyze the data. Values of D range from 5.7 exp (−58.000 cal/ RT) cm 2/ sec at 2 w/o Co to 0.6 exp (−51.000 cal/ RT) cm 2/ sec at 0.1 w/o Co. Extrapolation to very low cobalt concentrations is difficult, and different procedures give widely differing results.

Electrochemical Reduction of Potassium Chromate in the Presence of Zinc(II) and Cobalt(II) in Molten Lithium Chloride‐Potassium Chloride Eutectic

The electrochemical reduction of in molten eutectic is shifted to more positive potentials by the addition of or . In the case of added three electrons are consumed per mole of and an insoluble reduction product having the empirical formula is obtained. In the presence of , the reaction product depends on the electrolytic conditions, especially the cathodic potential. The limiting processes appear to be a two‐electron process, favored by low cathodic potential and high cobalt (II) concentration to yield , and a three electron process, favored by high cathodic potential and low cobalt (II) concentration to yield . A mechanism consistent with these observations is proposed.

New oxo chemistry via solid polymer-cobalt carbonyl complexes

Solid poly-2-vinylpyridine polymers were used to complex cobalt carbonyls to form a unique hydroformylation system. This solid, polymer-cobalt carbonyl system serves as a catalyst reservoir which reversibly and rapidly releases enough cobalt carbonyl to override and/or destroy olefin feed poisons and to cause the homogeneous oxo reaction to proceed at a predictable rate without an induction period. Hence, oxo reactions may be run on either pure or impure olefin feeds at low cobalt concentrations. The soluble catalyst concentration was found to be a function of temperature and the polymer cobalt carbonyl concentration. Thirty to 40% of the nitrogen atoms within the polymer matrix are available for complexing cobalt carbonyls in a H 2/CO atmosphere.

Modified magnico alloys with a low cobalt concentration

Modified magnico alloys with a low cobalt concentration

Reactions of gases in solution. Part I. Products of the reaction of hydrogen with cobalt(II) cyanide complexes

The number and nature of the complexes formed when aqueous solutions of cobalt(II) cyanide complexes react with hydrogen have been investigated. Studies of the equilibria and u.v.–visible spectra in solution show that at least three different complexes may be produced. The main product is shown to be the [CoIII(CN)5H]3– ion, which has been isolated in the solid state as the salt Cs2Na[Co(CN)5H]. The same ion can be produced by reduction with borohydride or sodium amalgam. The cobalt–hydrogen and –deuterium stretching frequencies are 1860 and 1340 cm.–1, and bending frequencies 774 and 610 cm.–1, respectively, in the solid state. Aqueous solutions of the complex show an absorption band at 305–306 mµ(Iµmolar∼ 620), as already found by previous workers. A second complex, which is formed in solutions of low cobalt concentration and low ionic strength, contains less than five cyanide groups per cobalt and shows an absorption spectrum with the first d–d band at ∼300 mµ(Iµmolar∼ 660); its structure may be [CoIII(CN)4H2]. A third complex of possible structure [CoI(CN)6] is observed at high cyanide concentrations; its formation from [CoII(CN)5H2O] in the presence of hydrogen obeys an equilibrium involving one additional cyanide group.

2,3-Dihydroxybenzoate as a bacterial growth factor and its route of biosynthesis

2,3-Dihydroxybenzoate has been shown to be a growth factor in shaken cultures of certain multiple aromatic auxotrophs of Escherichia coli and Aerobacter aerogenes. The requirement for 2,3-dihydroxybenzoate is influenced by the presence of iron and citrate in the medium. The effects of the latter compounds differ with an auxotrophic strain derived from E. coli W and auxotrophic strains derived from E. coli K12. In the case of the former strain, certain metal ions or anaerobic growth will eliminate the 2,3-duhydroxybenzoate requirement; in the latter strains citrate replaces 2,3-dihydroxybenzoate. 2,3-Dihydroxybenzoate is formed via the shikimic acid pathway from chrismate in E. coli and A. aerogenes. The enzyme system forming 2,3-dihydroxybenzoate from choristmate in A. aerogenes has been studied and shown to require NAD and Mg 2+ for activity. At least two steps appear to be involved in the overall reaction. The enzyme system converting chorismate into 2,3-dihydroxybenzoate is strongly repressed by low concentrations of iron or cobalt and is also affected by the presence of salicylate or citrate in the growth medium.

The biological action of cobalt and other metals II. The mechanism of the respiratory inhibition produced by cobalt in mammalian tissues

1. 1. The intraperitoneal injection of 1.25 mg Co 2+ as cobalt chloride into rats caused a 25% depression in respiration of the liver within 21 h. 5 mg Co 2+ similarly injected produced this degree of respiratory inhibition within 15 min. 2. 2. When increasing amounts of cobalt were added to suspensions of isolated tissues the respiration progressively decreased, and then became essentially independent of the cobalt concentration. 3. 3. The oxidative activities of homogenates of liver and diaphragm were much more sensitive to inhibition by low concentrations of cobalt than the intact tissues; again, however, part of the respiration appeared insensitive to Co 2+. 4. 4. Homogenates of thigh muscle showed consistent oxidation of succinate, but not of other intermediates in the tricarboxylic acid cycle. The rates of oxidation of keto acids declined rapidly; this could be prevented by the addition of DPN or cobalt chloride to the medium, although cobalt also caused an initial inhibition of such oxidations. 5. 5. Cobalt caused by a very slight inhibition of glycolysis by liver homogenates, and an initial stimulation of glycolysis by muscle homogenates. 6. 6. Of the oxidations of tricarboxylic acid-cycle intermediates by rat-liver mitochondria, those of keto acids were most inhibited by cobalt. In addition, the accumulation of keto acids in suspensions of mitochondria with citrate as substrate was increased by the addition of 5 μg Co 2+/ml. 7. 7. Mitochondria of thigh muscle showed very low rates of oxidation of malate, fumarate and citrate. Keto acids were oxidized effectively; the oxidation of these substrates was readily inhibited by Co 2+. 8. 8. In the presence of concentrations of cobalt and arsenite that gave the same degree of respiratory inhibition, the rates of accumulation of keto acids from the metabolism of malate by mitochondria were similar. 9. 9. The presence of a metabolizable substrate increased the uptake of isotopically labelled cobalt by liver mitochondria by at least 14%; the cobalt taken up under these conditions was removed less readily. 10. 10. It is suggested that the action of cobalt, like that of arsenite, is due to complex formation between the ion and the dithiol form of lipoic acid, a coenzyme of keto acid dehydrogenation.

Magnetocrystalline anisotropy in cobalt-substituted magnetite single crystals

The growth of single crystals corresponding to x=0 (high-purity magnetite), x = 0.01 and x = 0.04 in the composition series CoxFe3-xO4 is described. First- and second-order anisotropy constants of these crystals are determined by the torque method over the temperature range 120–450°K. The substitution of small amounts of cobalt for iron is found to add a positive contribution to K1 and a negative contribution to K2. At low cobalt concentrations the magnitude of this contribution is a linear function of the amount of cobalt added. It is suggested that the effect of cobalt on the anisotropy is enhanced by the presence of divalent iron in magnetite, and it is concluded that the change in sign of K in magnetite at about 130°K is not caused by the presence of cobalt or any other foreign impurity.