Nickel criteria

Ordinarily, this principle is applied at standard concentrations (1 atm for gases, 1M for species in aqueous solution). Hence it is the sign of E° that serves as the criterion for spontaneity. To show how this works, consider the problem of oxidizing nickel metal to Ni2+ ions. This cannot be accomplished by using 1M Zn2+ ions ... 

For the cathode seal material, there is a criterion that the thermal expansion coefficient of the metal component must be lower than that of the a-alumina header. A nickel-cobalt-iron alloy (NiloK) with a... 

Table 6.10 Proposed Nickel Criteria for Protection of Natural Resources and Human Health Resource, Criterion, and Other Variables Effective Nickel Concentration Reference9... 

Resource, Criterion, and Other Variables Effective Nickel Concentration Reference8... 

In this section a method for the direct calorimetric determination of heats of adsorption on evaporated metal films is described and results for the heals of adsorption of hydrogen on nickel, iron, and tungsten are reported. In all cases the heats of adsorption decrease with the fraction of surface covered in a mode that can satisfactorily be explained by interaction of adsorbed atoms. A criterion for mobility of the adsorbed atoms is developed... 

That is, ttcr is directly proportional to K c/cry) since oh is a fraction of Oy. Thus, the larger the value of acr, the more attractive is the material, since cracks can be easily detected without the use of sophisticated equipment. The Ashby plot of fracture toughness versus density (Figure 8.10) indicates that of the three classes of materials selected with Criterion 1, only the engineering composites and engineering alloys provide suitable possibilities for Criterion 2. Again, of the alloys, titanium, steel, nickel, and copper alloys are the best here. 

The real power of the Ashby diagrams comes when we realize that we can combine Figures 8.9 and 8.10 to yield one, more useful diagram (Figure 8.11), namely a plot of fracture toughness versus strength. This plot shows unequivocally that the steel, nickel, and titanium alloys are the best classes of materials to select for this application. We will use Criterion 3 to narrow this field even further. 

Many other nickel complexes, some of which have been shown to be planar by the methods mentioned in Section 5-3, have been found to satisfy the magnetic criterion. These include the nickel glyoximes,81... 

It is well known, even from old literature data (ref. 1) that the presence of metal promotors like molybdenum and chromium in Raney-nickel catalysts increases their activity in hydrogenation reactions. Recently Court et al (ref. 2) reported that Mo, Or and Fe-promoted Raney-nickel catalysts are more active for glucose hydrogenation than unpromoted catalysts. However the effects of metal promotors on the catalytic activity after repeated recycling of the catalyst have not been studied so far. Indeed, catalysts used in industrial operation are recycled many times, stability is then an essential criterion for their selection. From a more fundamental standpoint, the various causes of Raney-nickel deactivation have not been established. This work was intended to address two essential questions pertinent to the stability of Raney-nickel in glucose hydrogenation namely what are the respective activity losses experienced by unpromoted or by molybdenum, chromium and iron-promoted catalysts after recycling and what are the causes for their deactivation ... 

The EPA mobile lab analyzed soil samples for lead, zinc, copper, and nickel by XRF. Because arsenic had been identified as the element that presents the greatest risk to human health at the Cos Cob site, samples from the 0—1 ft (0—0.3 m) to 1—2 ft (0.3-0.6 m) intervals were sent off-site for analysis by inductively coupled plasma/ atomic emission spectrometry. If the off-site analysis showed arsenic concentrations greater than 10 ppm (the Connecticut direct exposure criterion for soil), the field investigators progressively analyzed samples in 1 -ft (0.3 m) intervals below and surrounding the sample, delineating hot spots, until the remaining contamination was lower than 5 ppm. 

One of the properties of fossil fuels of interest to refiners is metal content. Vanadium in particular is troublesome in refinery operations (2). In some crude oils it occurs in concentrations up to 1000 ppm (3). Of the other metals in petroleum, only nickel is known to be present in concentrations approaching that of vanadium. These two metals are com-plexed with porphyrins and other ligands, the exact nature of which is unknown (4), Crude oils that are high in sulfur are usually high in vanadium (5), and it is interesting to determine whether or not this criterion also applies to tar sands. 

As noted above, the two-photon states become important for an 800 nm irradiating wavelength when complexes contain > 400 nm, and real components for the nickel complexes considered here become negative when the optical absorption maximum fulfils this criterion. Despite the large error margins, an increase in the real component of the nonlinearity upon chain-lengthening is evident, and an increase in efficiency upon replacing Z by stereochemistry, in... 

As shown in Table V, 2,3-dimethylbutane is the major reaction product in every case except for the cis isomer on platinum. Since both mechanisms A and B (nonselective and selective) compete on platinum films (86, 87), and probably as well on nickel and rhodium films, the excess of 2,3-dimethylbutane over the amounts expected by Mechanism A may be assigned to Mechanism B, involving the selective rupture of —CHj—CHj— bonds. a,a,, -Tetraadsorbed species were suggested to be associated with Mechanism B (89), whose contribution increases with different metals in the same order, Pt < Ni < Rh, as that for multiple exchange of methane (90). Since multiple exchange of methane is usually taken as a criterion for the ability of a metal to form adsorbed methylene, this result is in fair agreement with the proposed a,a,J ,)S-tetraadsorbed precursors (Scheme 34). The latter were... 

A closely analogous state of affairs is seen in the systems NiTe2-NiTe and TiTe2-TiTe, in which the AB2 compound has the cadmium iodide structure and the AB compound that of nickel arsenide. In both of these structures the B atoms are arranged as in hexagonal close-packing, but in other respects the relationship between them is precisely the same as that between the cadmium chloride and sodium chloride structures, so that solid solution can take place by the same mechanism. Examples such as this, and many others which could be quoted, emphasize that solid solution is in no sense a satisfactory criterion for isomorphism, and that substances may form solid solution even if their structures are formally quite different. 

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