Cobalt compared with nickel

Cobalt cannot be classified as an oxidation-resistant metal. Scaling and oxidation rates of unalloyed cobalt in air are 25 times those of nickel. The oxidation resistance of Co has been compared with that of Zr, Ti, Fe, and Be. Cobalt in the hexagonal form (cold-worked specimens) oxidizes more rapidly than in the cubic form (annealed specimens) (3). 

Similar calculations were carried out for the single impurity systems, niobium in Cu, vanadium in Cu, cobalt in Cu, titanium in Cu and nickel in Cu. In each of these systems the scattering parameters for the impurity atom (Nb, V, Co, Ti or Ni) were obtained from a self consistent calculation of pure Nb, pure V, pure Co, pure Ti or pure Ni respectively, each one of the impurities assumed on an fee lattice with the pure Cu lattice constant. The intersection between the calculated variation of Q(A) versus A (for each impurity system) with the one describing the charge Qi versus the shift SVi according to eqn.(l) estimates the charge flow from or towards the impurity cell.The results are presented in Table 2 and are compared with those from Ref.lc. A similar approach was also found succesful for the case of a substitutional Cu impurity in a Ni host as shown in Table 2. 

Klenke et al. [5] described a technique for extraction of humic and fulvic acids from stream sediments and outlined methods for their determination. By means of flame atomic absorption spectrometry, the levels of environmentally important heavy metals (cadmium, copper, chromium, cobalt, nickel and lead) in the fulvic and humic acid extracts were compared with those in the original sediment samples. The pattern distribution of the respective metals in the two cases showed very close agreement, suggesting that the combined extract of humic and fulvic acids could be used as an indicator of the level of heavy metal pollution in flowing waters. 

There have been few studies of substitution in complexes of nickel(II) of stereochemistries other than octahedral. Substitution in 5-coordinated and tetrahedral complexes is discussed in Secs. 4.9 and 4.8 respectively. The enhanced lability of the nickel(II) compared with the cobalt(II) tetrahedral complex is expected from consideration of crystal field activation energies. The reverse holds with octahedral complexes (Sec. 4.8). 

For simple acidic extractants, such as carboxylic or sulfonic acids, the similarity in formation constants does not produce cobalt-nickel separation factors (Sn° 2) sufficiently large for commercial operation (Fig. 11.4). Data for pH versus extraction for some chelating acid extractants does seem to offer the possibility of separation [e.g., for the hydroxyoxime Acorga P50, the pHso for nickel(II) is 3.5 and for cobalt(II) 5.0]. Normally, this pH difference would be suitable for a separation process, but this particular system has hidden complications. The rate of nickel extraction is very slow compared with cobalt and, in addition, although cobalt is initially extracted... 

Small metal particles can also be obtained by vacuum evaporation in low pressure inert gases (16). Magnetic particles of metals such as iron, cobalt, nickel, and alloys of these metals can be prepared by this method. Though the amounts of particles obtainable by this method are limited, the particles are clean as compared with particles precipitated from solutions. They are mainly used for studies of physical properties of fine particles. 

Molybdena catalysts containing nickel have received relatively less attention as compared with cobalt. Nickel-molybdena catalysts show... 

How do the monoxides of chromium, manganese, iron, cobalt, and nickel compare in basic strength with the oxides of copper and zinc and with the oxides of the alkali and alkaline earth metals How do the sesquioxides, R203, compare with the monoxides of this group as regards basic strength ... 

It is now widely accepted that the activation of CO is highly structure sensitive (II). The activation of CO on most of the transition metals has been investigated. The computational results for cobalt (6) and ruthenium (5) are of particular relevance to us because these elements in the metallic state are active for the Fischer-Tropsch reaction. These results can be compared with those obtained for rhodium (40), which selectively catalyzes the formation of alcohols from CO and H2, and for nickel (30), which is a methanation catalyst. 

The results for the deuteration of 2-, 3-, and 4-picolines are summarized in Table IX. With 2-picoline, specific deuteration in the a-position only is observed on cobalt, whereas platinum is catalytically active for all positions,105 as is nickel chloride which catalyzes deuteration of the methyl group in particular. As with pyridine, borohydride-reduced oxide catalysts are more active than self-activated preparations. The much higher reactivity in 2-picoline compared with pyridine in selfactivation indicates that the methyl group compensates for deactivation from the nitrogen lone pair. Hydrogen for self-activation in the former compound originates predominantly from the methyl group. 

The extraction of cobalt from arsenical concentrates consisting of autooxidation acid leaching under pressure, separation, purification, hydrogen reduction of ammoniacal leach solution, and removal of sulfur and granulation of the metal was described by Mitchell (M37). The final product contained 95.6% cobalt, 3.90% nickel, and 0.03% arsenic compared to the feed concentrate with an assay of 17.5% cobalt, 1% nickel, and 24% arsenic. 

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