Nickel atomic weight

Corrosion Rate by CBD Somewhat similarly to the Tafel extrapolation method, the corrosion rate is found by intersecting the extrapolation of the linear poi tion of the second cathodic curve with the equihbrium stable corrosion potential. The intersection corrosion current is converted to a corrosion rate (mils penetration per year [mpy], 0.001 in/y) by use of a conversion factor (based upon Faraday s law, the electrochemical equivalent of the metal, its valence and gram atomic weight). For 13 alloys, this conversion factor ranges from 0.42 for nickel to 0.67 for Hastelloy B or C. For a qmck determination, 0.5 is used for most Fe, Cr, Ni, Mo, and Co alloy studies. Generally, the accuracy of the corrosion rate calculation is dependent upon the degree of linearity of the second cathodic curve when it is less than... 

The atomic weight increases regularly across the row except for the inversion at cobalt and nickel. We would expect the atomic weight of Ni to be higher than that of Co because there are more protons (28) in the Ni nucleus than in the Co nucleus (27). The reason for the inversion lies in the distribution of naturally occurring isotopes. Natural cobalt consists entirely of the isotope 2 Co natural nickel consists primarily of the isotopes Ni and Ni, the 58-isotope being about three times as abundant as the 60-isotope. 

Wurtz s point about cobalt and nickel is well taken given that classification was by atomic weight there would have been no basis for the prediction of two elements between iron and copper, had neither cobalt or nickel been known, and no basis for predicting the existence of the other had only one of them been known. 

Nickel was first isolated in 1751, and a relatively pure metal was prepared in 1804. In nature, nickel is found primarily as oxide and sulfide ores (USPHS 1977). It has high electrical and thermal conductivities and is resistant to corrosion at environmental temperatures between -20°C and +30°C (Chau and Kulikovsky-Cordeiro 1995). Nickel, also known as carbonyl nickel powder or C.I. No. 77775, has a CAS number of 7440-02-0. Metallic nickel is a hard, lustrous, silvery white metal with a specific gravity of 8.9, a melting point of about 1455°C, and a boiling point at about 2732°C. It is insoluble in water and ammonium hydroxide, soluble in dilute nitric acid or aqua regia, and slightly soluble in hydrochloric and sulfuric acid. Nickel has an atomic weight of 58.71. Nickel is... 

Nickel is known to have a face-centered cubic (fee) type of crystal structure. The atomic density of the metal is 9.14 X lO atoms/cm, the atomic weight is 58.73, and the density (p) is 8.91 g/cm. ... 

Person 2 Look up the density and atomic weight of nickel in Tables 1.11 and 1.3, respectively, and calculate the number of atoms per cubic meter for nickel. (Don t forget Avogadro s number.)... 

With the assumption that the 4100 structures have equal weights, the carbon-carbon bonds in the ring are calculated to have bond number n = 1.173 and the nickel-carbon bonds to have n = 0.439, with 34.6 percent d character for the nickel bond orbitals. The number of unshared pairs on the nickel atom is 2.89. The formal charge on the nickel atom is —0.64 of this, the 4.39 Ni—C bonds, with 12 percent ionic character, would provide the opposite charge -f 0.53, leaving the nickel atom essentially neutral (charge —0.11). 

The first enzyme that was demonstrated to contain nickel was urease (urea amidohydrolase) from jack bean. It catalyzes the hydrolysis of urea to ammonia and carbon dioxide. The protein has a multimeric structure with a relative molecular mass of 590,000 Da. Analysis indicated 12 nickel atoms/mol. Binding studies with the inhibitors indicated an equivalent weight per active site of 105,000, corresponding to 2 nickel atoms/active site. During removal of the metal by treatment with EDTA at pH 3.7, the optical absorption and enzymatic activity correlated with nickel content. This, combined with the sensitivity of the enzyme to the chelating agents acetohydroxamic acid and phos-phoramidate, indicates that nickel is essential to the activity of the enzyme (1). 

This brings the three elements into complete harmony with the general scheme. It is always possible that further research may ultimately prove, in a similar manner, that nickel and cobalt are not real, but only apparent, exceptions to the Periodic Law. It must be admitted, however, that this is very unlikely, since it necessitates either very considerable errors in the modem determinations of their atomic weights, or the assumption that one or both of these elements is in reality complex. 

The most recent views on the Periodic Classification suggest an entirely different method of removing the anomaly, namely, that the atomic weight is not the correct property to use in arranging the elements rather should one be chosen which increases by a constant amount in passing from one element to the next. Physical theory indicates the positive nuclear charge of the atom to be one such property, whilst experimentally it is found that the X-ray spectra afford such a property, and eliminate the nickel-cobalt anomaly.1... 

Moissan 3 in 1880 called attention to the fact that the affinities of chromium, manganese, iron, cobalt, and nickel for oxygen and the heats of formation of oxides, chlorides, bromides, iodides, and sulphides decrease as the atomic weights rise. 

The most appropriate position for cobalt in the Periodic Table is, as explained in the opening chapter of this volume, between iron and nickel. Assuming the atomic weights of iron and nickel to be correct, we should expect the value for cobalt to be greater than 55-84 (at. wt. of iron), but less than 58-68 (at. wt. of nickel). 

In preparing a specimen of pure nickel for atomic weight purposes Winkler 2 employed the following solution ... 

Atomic Weight.—Approximate Atomic Weight.—That the atomic weight of nickel is approximately 59, and not a multiple or submultiple of this amount, is evident from various considerations ... 

The specific heat of nickel is 0-109. Assuming a mean atomic heat of 6-4, the atomic weight, according to Dulong and Petit s Law, is approximately 58-7. 

The most appropriate position for nickel in the Periodic Table is, as explained in Chapter I, the end of the first horizontal series of triads in Group VIII. An atomic weight greater than that of cobalt, namely, 58-97, but less than that of copper, namely, 63-57, is thus to be expected. 

Analyses of the compounds indicate that the atomic weight of nickel is 58-68,... 

Exact Atomic Weight.—In. 1826 Rothoff,1 in a single experiment, found that 188 parts of nickel monoxide are equivalent to 718-2 parts of silver chloride whence2 Ni — 59-OS... 

In 1852, Erdmann and Marchand,3 by reducing nickelous oxide in hydrogen, obtained values for the atomic weight of nickel varying from 58-2 to 58-6. In 1856, in a single experiment, Deville arrived at a value 59-3 for the atomic weight.4... 

The atomic weights given by the first two ratios should be increased by 0-015, to allow for the presence of the trace of sodium bromide present. The third ratio requires no such correction as the weights of the nickel bromide were corrected before computing the ratio. The corrected atomic weight values are accordingly 58-683, 58-680, and 58-682. 

Date. Experimenter. No. of Expts. Ratio measured. Atomic weight of nickel. 

Hence, the atomic weight of nickel is Ni = 58 68, which value is adopted by the International Committee in their Table of Atomic Weights for 1918,... 

By accepting this figure for the atomic weight of nickel we are at once confronted with a difficulty in so far as the Periodic Table is concerned. 

Cobalt, in its properties, is an excellent intermediary between iron and nickel, and, moreover, it is clearly a suitable element to constitute the first of the central vertical triads of Group VIII, namely, Co, Eh, and Ir. Hence, if the Periodic Law holds absolutely, the atomic weight of cobalt should exceed that of iron, but not that of nickel. Either, therefore, the atomic weight of cobalt is slightly too high or that of nickel is slightly too low. 

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