Nickel oxide equilibrium with

Bale) and Divisek re-evaluated qualitatively equilibrium or rest potentials of solid nickel oxide hydroxides with 2 < z(Ni) < 3.6 measured at ambient temperatures. The experimental data were converted to standard conditions i.e., 25°C, ukoh 1-0, E... 

Fig. 20. Thermograms recorded during the adsorption of doses of oxygen on nickel oxide at 30°C, the equilibrium pressure of the gas being smaller (A) or larger (B) than 10 a Torr. Reprinted from (19) with permission.

Methods. The differential heats of adsorption of reagents and the differential heat of their interaction on the nickel oxide surface were measured in a Calvet microcalorimeter with a precision of 2 kcal. per mole. The apparatus has been described (18). For each adsorption of a single gas, small doses of gas are allowed to interact with a fresh nickel oxide sample (100 to 200 mg.) placed in the calorimeter cell maintained at 30°C. At the end of the adsorption of the last dose, the equilibrium pressure is, in all cases, 2 torr. Duplication of any adsorption experiment on a new sample gives the same results within 2 kcal. per mole of heat evolved and 0.02 cc. of gas adsorbed per gram. Electrical conductivities of the nickel oxide sample are measured in an electrical conductivity cell with platinum electrodes (1) by a d.c. bridge. 

Conditioning of the manganese oxide suspension with each cation was conducted in a thermostatted cell (25° 0.05°C.) described previously (13). Analyses of residual lithium, potassium, sodium, calcium, and barium were obtained by standard flame photometry techniques on a Beckman DU-2 spectrophotometer with flame attachment. Analyses of copper, nickel, and cobalt were conducted on a Sargent Model XR recording polarograph. Samples for analysis were removed upon equilibration of the system, the solid centrifuged off and analytical concentrations determined from calibration curves. In contrast to Morgan and Stumm (10) who report fairly rapid equilibration, final attainment of equilibrium at constant pH, for example, upon addition of metal ions was often very slow, in some cases of the order of several hours. 

There are a few examples of spin equilibria with other metal ions which have not been mentioned above. In cobalt(III) chemistry there exist some paramagnetic planar complexes in equilibrium with the usual diamagnetic octahedral species (22). The equilibria are the converse of the diamagnetic-planar to paramagnetic-octahedral equilibria which occur with nickel(II). Their interconversions are also presumably adiabatic. Preliminary observations indicate relaxation times of tens of microseconds, consistent with slower ligand substitution on a metal ion in the higher (III) oxidation state (120). 

Tile partially purilied synthesis gas leaves the C02 absorber containing approximately 0.1% CO2 and 0.5% CO. This gas is preheated at the methanator inlet by heat exchange with the synthesis-gas compressor interstage cooler and the primary-shift converter effluent and reacted over a nickel oxide catalyst bed in the methanator. The methanation reactions are highly exothermic and are equilibrium favored by low temperatures and high pressures. 

If the rich gas from the CRG reactor is passed over another bed of high-nickel catalyst at a lower temperature, the equilibrium of the five components is reestablished. Carbon oxides react with hydrogen to form methane and the calorific value of the gas is increased. It should be noted that this methanation step differs from that encountered in ammonia synthesis gas production because of the high steam content the temperature rise is reduced and there is no possibility of temperature runaway as the... 

The difference to the copper process is, that the reduction of nickel oxide with methane is an endothermic process, thus a heat engine could be employed. Figures 9 and 10 show the enthalpy, entropy diagrams of the reactions outlined in equations (8) and (9). (A metallurgist will not favor the reoxidation of nickel since it is very difficult, but equilibrium thernodynamic considerations do allow it.)... 

The acidification of H2 may also be involved in hydrogenase action, where H2 is beheved to bind to an Fe(II) center. Isotope exchange between H2 and D2O is catalyzed by the enzyme see Nickel Enzymes Cofactors Nickel Models of Protein Active Sites Iron-Sulfur Proteins). Similar isotope exchange can also occur in H2 complexes. Oxidative addition to give a classical dihydride is also a common reaction. [W(H2)(CO)3(PCy3)2] is in equilibrium with about 20% of the dihydride in solution. This can lead to subsequent hydrogenolysis of M-C bonds as in the case of a cyclometallated phenylpyridine complex of Ir(III). ... 

To obtain good conversion by reaction (4) even with an excess of steam It is necessary to use an active catalyst in order to operate at a temperature lower than 1000° C. Nickel catalysts, promoted with alumina or thoria and supported on fire clay, magnesium oxide, or brick, are very suitable for the process, giving essentially equilibrium conversion at low rates of gas flow through the converter. At increasing rates of flow the increase in unconverted methane is practically linear with the increase in space velocity. ... 

Mixtures of metallic nickel and nickel oxide were treated with CO/CO2 gas mixtures at temperatures between 1044 and 1289 K. The composition of the gas phase after equilibration with the solid phases was determined by chemical analysis, yielding equilibrium constants for the reaction ... 

A mixture of metallic nickel and nickel oxide (particle size around 1 pm) was treated with mixtures of water vapour and hydrogen gas at temperatures ranging from 711 to 860 K, The ratio of equilibrium partial pressures was determined by a ten-... 

In some systems in which nickel sulfide catalysts are used, the nickel is initially introduced into the catalytic reactor either in the form of the metal or of the oxide. The equilibrium between nickel and sulfur-containing reactants (H S, CSz, etc.) is established in a short time, so that the resulting nickel sulfide corresponds to the solid phase which is in equilibrium with the reacting components at the temperature and partial Contribution from The International Nickel Company Fellowship, Mellon Institute, Pittsburgh, Pa. 

The nickel(IV) oxime, bis(6-amino-3-methyl-4-azahexa-3-ene-2-one oxime)nickel(IV), and the nickel(III) oxime, (15-amino-3-methyl-4,7,10,13-tetraazapentadeca-3-ene-2-one oxime)nickel(III), complexes react with hydro-quinone. Proton-related equilibria for both the nickel complexes and the hydroquinone could be elucidated from the kinetic details. For reactions with the complexes and the hydroquinone could be elucidated from the kinetic details. For reactions with the Ni(III) complex there is evidence of an inner-sphere process. The [NiL(TCCat)] complex (TCCatH2 = tetrachlorocatechol L = 2,4,4-trimethyl-1,5,9-triazacyclododec-l-ene) forms a 1 1 adduct with tetrachloro-1,2-benzoquinone. Spectroscopic evidence suggests that this compound can be described formally as a quinone adduct of a Ni(I)-semiquinone moiety arising from inner-sphere ligand oxidation. The crystallographically determined structure (11) is shown below. Several copper complexes of a vareity of semiquinones also exist in solution in equilibrium with the corresponding catechol complexes. ... 

A new strategy for the synthesis of xanthophylls was developed in the 1970s by Roche [77]. The cyclic moieties are all derived from the common precursor 6-oxoisophorone (68), which is obtained from inexpensive a-isophorone (69) in two steps. In the liquid phase in the presence of weak acids, or in the gas phase on nickel oxide catalysts [78,79], 69 is in equilibrium with p-isophorone (70), which may be separated from the higher-boiling starting material by fractional distillation (Scheme 21). 

---