Cobalt occurrence

Cobalamin, 25 803 folic acid and, 25 802 Cobalt (Co), 7 207-228. See also Co-base superalloys 60Co isotope 60Co nucleus Fe-Ni-Co alloys Dicobalt octacarbonyl Tetracobalt dodecacarbonyl analysis, 7 215-216 in ceramic-matrix composites, 5 554t coke formation on, 5 266 colloidal suspensions, 7 275 economic aspects, 7 214-215 effect on copper resistivity, 7 676t environmental concerns, 7 216 health and safety factors, 7 216-218 in M-type ferrites, 11 66, 69 occurrence, 7 208... 

Use of the kinetic advantage method thus points clearly to the occurrence of chemical catalysis with the low-valent metalloporphyrins. This is confirmed by repeating, with iron(I) octaethylporphyrin and cobalt (I) etioporphyrin, the stereochemical experiments carried out earlier with the anion radical of 1,4-diacetylbenzene. Complete stereospecificity is observed in both cases The meso isomer of 4,5-dibromooctane is converted totally into the c/.v-olcfin the d,l isomer is converted totally into the trans-olefin. The reaction again exhibits a clear antiperiplanar preference. 

Occurrence. There are a number of important ores containing cobalt. These include linnaeite, Co3S4, cobaltite, CoAsS, and smaltite, CoAs2. 

Occurrence. Arsenic is associated with sulphide minerals (As4S4 realgar, As2S3 orpiment, FeAsS arsenopyrite, Cu3AsS4, enargite, etc.). Occasionally arsenic is found as free element, usually in ore containing cobalt, antimony, nickel. 

Formate esters of the various alcohols formed are observed as major products in these cobalt-catalyzed reactions, and the mole ratio of formates to alcohols remains constant throughout a reaction. This observation would be consistent with the occurrence of a rapid carbonylation equilibrium process,... 

Jhe distribution of beryllium, boron, titanium, vanadium, chromium, cobalt, nickel, copper, zinc, gallium, germanium, tin, molybdenum, yttrium, and lanthanum in the principal coal-producing beds of the Interior Province has been studied by the U. S. Geological Survey. Data, methods of sampling, and analyses are discussed by Zubovic and others (II, 12). This chapter discusses the occurrence of 13 of these elements with respect to geological and geochemical environments of coal deposition and chemical properties of the elements. Zinc and tin are not included in this study because they were detected in only a few samples. 

The d-spacings of the 211 (d = 33.1 A) and 220 (d = 28.6 A) reflections of the pristine MCM-48 silica are observable in the host/guest compounds whereas the higher order reflections (20 4-6°) disappear. In addition, the 113/021 (d = 2.53 A 1=100%) and 208/220 (d = 1.48 A 1=36%) reflections of the inverse cobalt iron structure appear in sample A and B. In contrast to the bulk material of CoFe24 (figure 2) synthesized under exact the same conditions as the phases A and B, the reflections of the host/guest compounds are much broader and weaker in intensity, indicating the occurrence of very small particles. 

Alginates 170,178 Alkali metal ions 206 Alkaline phosphatases 645 active site of 645 occurrence 645 Alkane(s) 382 Alkenes, hydration of 683 Alkyl shift, rearrangements with 527 Alkyl cobalt 867 Alkyl ethers 382 Alkyl cobalamms... 

Structural, thermodynamic, and kinetic studies have shown that hydroxo-bridged polynuclear complexes of (diromium(III), cobalt(III), rhodium(III), and iridium(III) have many general features in common. Structurally, the four metal ions exhibit an almost identical pattern, and in particular the occurrence of many well-characterized oligomers... 

Skutterudite is found in moderate-temperature veins, commonly associated with other cobalt/nickel minerals, e.g., cobaltite and nickeline. The mineral was named for its occurrence at Skutterud, Norway. Important ore sources are Norway. Bohemia. Saxony, Spain. France, and New South Wales, Australia Notable occurrences are in Ontario. Canada, mainly Sudbury, South Lorrain, and Gowganda. 

The above studies indicate that metal ions catalyze the hydrolysis of amides and peptides at pH values where the carbonyl-bonded species (25) is present. At higher pH values where deprotonated complexes (26) can be formed the hydrolysis is inhibited. These conclusions have been amply confirmed in subsequent studies involving inert cobalt(III) complexes (Section 61.4.2.2.2). Zinc(II)-promoted amide ionization is uncommon, and the first example of such a reaction was only reported in 1981.103 Zinc(II) does not inhibit the hydrolysis of glycylglycine at high pH, and amide deprotonation does not appear to occur at quite high pH values. Presumably this is one important reason for the widespread occurrence of zinc(Il) in metallopeptidases. Other metal ions such as copper(II) would induce amide deprotonation at relatively low pH values leading to catalytically inactive complexes. 

A severe problem in the preparation of these iron and cobalt rich materials is the occurrence of iron-rich impurity phases like Sm2Fei7 and/or SmFe3 that can irreversibly affect the property measurements. For that reason, magnetic data are only accessible for La6Coi3Pb, Pr6Fei3Pb, and Nd6Fei3Pb. 

Hence, none of the two above-mentioned criteria can be used as a reliable basis for predicting the sequence of occurrence of chemical compound layers in multiphase binary systems. The experimental data on the formation of nickel and cobalt silicides provides additional evidence for the validity of this conclusion. 

Table 3.8. Data of electron probe microanalysis of the Co-Zn diffusion zone. Cracked Co-Zn reaction couple the layers of the y and yi phases grew between cobalt and the 72 phase. Temperature 350°C, annealing time 72 ks (20 h), with the time of crack occurrence being uncertain... 

To determine the frequency of occurrence of mercury-containing particles in FDR, promptly collected residue from the discharge of mercury fulminate-primed ammunition was examined. Results are given in Table 22.1. In the first firing a small proportion of the particles also contained one of the following elements cobalt (trace), magnesium (trace), nickel (trace), and phosphorus (minor and trace). 

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