The determination of carbon in nickel

According to Analyse der Metalle (44) the procedure used for ferro-alloys and for refractory metals is also valid for nickel. Samples of up to 1 g can be analyzed in the form of chips. As fluxing agents 0.5 to 1 g low carbon iron are used as basis in the combustion boat, and 0.5 g tin chips -respectively 0.25 g tin chips and 0.25 g granulated bismuth - as cover for the sample. Combustion is carried out in a tube furnace at 1350 to 1400°C. Carbon dioxide is determined by coulometry or by conductometry. 

Kraft and Kahles (45) found that nickel cannot be burnt at 1200 C without flux or with a copper flux. Using iron granulates or millings in a flux 

Remark A long period of combustion is recommended because the sample does not fuse at 1200 to 1300°C. In routine work the period of combustion may be reduced to 15 to 20 min if the rate of flow of oxygen is increased to 800 to 1000 ml/min.  

Although the other nuclear reactions e.g. C( He,a) C were sometimes 12 13 

---

Strijckmans et al. (52) describe the determination of carbon in nickel. After irradiation with 7 MeV deuterons (degraded to 4.1 - 5.0 MeV) the sample is chemically etched in 3 volumes 40 % hydrofluoric acid and 2 volumes 14 M nitric acid and partly dissolved in 25 ml of a solution of 140 mg/1 ammonium hexachloroplatinate in 6 M hydrochloric acid. The ammonium hexachloroplatinate is added to speed up the dissolution. 30 min. is sufficient to dissolve 0.14 - 0.30 g/cm. The volume is adjusted to 50 ml... 

The determination of oxygen in nickel is a comparatively simple task. The frequent use of nickel as a bath metal for the analysis of other metals, mainly of higher melting point, has indeed shown that oxygen present in nickel reacts quantitatively and rapidly with carbon to form... 

Analytical Analyses. The potassium remaining in the coal ash was determined with a Perkin-Elmer model 303 atomic absorption spectrophotometer after performing a J. Lawrence Smith ignition on the sample. To obtain a total potassium balance it was necessary to recover the potassium that adhered to the nickel catalyst by digesting the catalyst with acid and determining the potassium by atomic absorption. The amount of carbonate in the ash was determined by treating the ash with 1 1 HC1 solution. The evolved gases were scrubbed, and the C02 was absorbed in Ascarite. 

Olefins and acetylene show rapid dissociation and the diffusion of carbon through nickel has been suggested for the rate-determining step [33] [383] which is in line with the activation energy for carbon formation being close to that for the diffusion of carbon through nickel. 

The most important degradative method for the determination of urea in the natural water samples is based on its conversion to carbon dioxide and ammonia by hydrolysis obtained with a nickel metalloenzyme (urease). In the manual procedure outlined by McCarthy [89] for the analysis in seawater, the enzymatic hydrolysis of urea was carried out at 50°C for 20 min, in the range of pH from 6.4 to 8.0, using a solution of crude lyophilized jack beam urease. After the samples were cooled at room temperature, NH4 concentration was determined by manual colorimetric method after cooling the samples at room temperature. The ambient concentration of NH4 and the analytical blank (NH4 contained in the reagents and in the urease solution) have to be subtracted for any sample to obtain the concentration of urea. In this reference study, the precision (RSD) was 1% at the concentration of urea equal to 1 pmol N A manual indirect methodology was also described by Katz and Rechnitz [209] and the method was revised in other following studies [9,53,197,198]. It persists with minor modifications in recent works on the field and in culture experiments [71,199-202] and for determination of isotope ratio in urea by elemental... 

Specimen preparation is simple, involving compressing a disc of the polymer sample for insertion in the instrument, measurement time is usually less than for other methods, and X-rays interact with elements as such, i.e., intensity measurement of a constituent element is independent of its state of chemical combination. The technique has some drawbacks, and these are evident in the measurement of cadmium and selenium. For example, absorption effects of other elements present, e.g., the carbon and hydrogen of a PE matrix, and excitation of one element by X-rays from another, e.g., cadmium and selenium affect one another. The technique has been applied to the determination of metals in polybutadiene, polyisoprene, and polyester resins [1]. The metals determined were cobalt, copper, iron, nickel and zinc. The samples were ashed, and the ash dissolved in nitric acid before X-ray analysis. Concentrations as low as 10 ppm can be determined without inter-element interference. 

Kolbel et al. (K16) examined the conversion of carbon monoxide and hydrogen to methane catalyzed by a nickel-magnesium oxide catalyst suspended in a paraffinic hydrocarbon, as well as the oxidation of carbon monoxide catalyzed by a manganese-cupric oxide catalyst suspended in a silicone oil. The results are interpreted in terms of the theoretical model referred to in Section IV,B, in which gas-liquid mass transfer and chemical reaction are assumed to be rate-determining process steps. Conversion data for technical and pilot-scale reactors are also presented. 

It must be acknowledged, however, that the determination of the number of the different surface species which are formed during an adsorption process is often more difficult by means of calorimetry than by spectroscopic techniques. This may be phrased differently by saying that the resolution of spectra is usually better than the resolution of thermograms. Progress in data correction and analysis should probably improve the calorimetric results in that respect. The complex interactions with surface cations, anions, and defects which occur when carbon monoxide contacts nickel oxide at room temperature are thus revealed by the modifications of the infrared spectrum of the sample (75) but not by the differential heats of the CO-adsorption (76). Any modification of the nickel-oxide surface which alters its defect structure produces, however, a change of its energy spectrum with respect to carbon monoxide that is more clearly shown by heat-flow calorimetry (77) than by IR spectroscopy. 

Temperature plays an important role in determining the amount and type of the carbon deposit. Generally during FTS at higher temperatures the amount of carbon deposited will tend to increase,30-31 but the case is often not so straightforward. An example of temperature dependence on the rate of carbon deposition and deactivation is the case of nickel CO hydrogenation catalysts, as studied by Bartholomew.56 At temperatures below 325°C the rate of surface carbidic carbon removal by hydrogenation exceeds that of its formation, so no carbon is deposited. However, above 325°C, surface carbidic carbon accumulates on the surface... 

Lee [524] described a method for the determination of nanogram or sub-nan ogram amounts of nickel in seawater. Dissolved nickel is reduced by sodium borohydride to its elemental form, which combines with carbon monoxide to form nickel carbonyl. The nickel carbonyl is stripped from solution by a helium-carbon monoxide mixed gas stream, collected in a liquid nitrogen trap, and atomised in a quartz tube burner of an atomic absorption spectrophotometer. The sensitivity of the method is 0.05 ng of nickel. The precision for 3 ng nickel is about 4%. No interference by other elements is encountered in this technique. 

The erosion effects of cavitation on solid surfaces have been extensively investigated both in terms of surface erosion [68] and corrosion [69]. The consequences of these effects on metal reactivity are important since passivating coatings are frequently present on a metal surface (e. g. oxides, carbonates and hydroxides) and can be removed by the impacts caused by collapsing cavitation bubbles. An illustration can be found with the activation of nickel powder and the determination of the change in its surface composition under the influence of cavitation by Auger spectroscopy (Fig. 3.6) [70]. 

The catalysts with metals are previously impregnated with solutions of vanadyl and nickel naphtenates based on the Mitchell method [4], Before hydrothermal deactivation the samples were calcined in air at 600°C. The activity was performed in the conventional MAT test using 5 grams of catalyst, ratio cat/oil 5, stripping time 35 seconds, and reaction temperature 515°C. Elemental analyses to determine the total amount of carbon in the spent catalysts were done by the combustion method using a LECO analyzer. 

One type of chemical approach to the analysis of liquid and solid hydrocarbons that will probably see considerable development is that involving reaction or complex formation to yield precipitates that can be separated from the unreacted mass and subsequently be treated to regenerate the hydrocarbons or class of hydrocarbons so precipitated. This field is certainly not extensively developed. In fact very few examples come to mind but among these are Gair s (21) determination of naphthalene by precipitation with picric acid determination of benzene by Pritzker and Jungkunz (52) by an aqueous solution of specially prepared nickel ammonium cyanide Bond s (8) nitrous acid method for styrene and more recently the determination of normal alkanes in hydrocarbons of more than 15 carbon atoms by adduct formation with urea as described by Zimmerschied et al. (71). 

Electron spin resonance was first applied to coal during the 1950s (Ingram et al., 1954 Uebersfeld et al., 1954) as a method for the determination of free-radical species in coal. Since that time, electron spin resonance has been used to compare the data for coals of different rank and to explore the potential for relating the data to the various carbon systems as well as offering valuable information about aromaticity (Toyoda et al., 1966 Retcofsky et al., 1968, 1978 Petrakis and Grandy, 1978 Kwan and Yen, 1979 Khan et al., 1988 Thomann et al., 1988 Nickel-Pepin-Donat and Rassat, 1990 Bowman, 1993 Sanada and Lynch, 1993). 

The analysis of petroleum feedstocks for the percentages of carbon, hydrogen, nitrogen, oxygen, and sulfur is perhaps the first method used to examine the general nature, and perform an evaluation, of a feedstock. The atomic ratios of the various elements to carbon (i.e., H/C, N/C, O/C, and S/C) are frequently used for indications of the overall character of the feedstock. It is also of value to determine the amounts of trace elements, such as vanadium and nickel, in a feedstock since these materials can have serious deleterious effects on catalyst performance during refining by catalytic processes. 

---