The determination of oxygen in nickel

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 

---

Strijckmans et al. (214) and Valladon et al. (241)(242) describe the determination of oxygen in nickel, resp. by helium-3 and triton activation. In... 

Between brackets number of participating laboratories 5.4 THE DETERMINATION OF OXYGEN IN NICKEL... 

The method u i g no ath at 2200 C is based on the M0-M0C2 eutectic, which is liquid at this temperature. Its use for the determination of oxygen in molybdenum was first discussed by Friedrich and Lassner (153)(172) and Friedrich et al. (172). Lassner and Schedle (174) find that it is suitable and yields results agreeing with those given by the procedure employing nickel-iron baths, both for powders and for compact samples. 

The determination of oxygen in tungsten by helium-3 activation is described by Vandecasteele et al. (247) and by Revel and Albert (240). Vandecasteele et al. (247) irradiated for 20 min with a 1.5 mA beam of 20 MeV helium-3. The sample was chemically etched in a 1/1 mixture of hydrofluoric and nitric acids, rinsed and dried. The energy corresponding to the etched depth was 13.5 - 14.2 MeV. The sample was dissolved in a mixture of 10 g of sodium hydroxide, 400 mg of sodium fluoride and 2.5 g of sodium nitrate in a nickel crucible. The melt was dissolved in nitric acid and F was... 

It is, of course, not necessary to use a heat-flow microcalorimeter in order to determine the heat released by rapid adsorption phenomena. Dell and Stone (74), for instance, using an isoperibol calorimeter of the Garner-Veal type, found an initial heat of 54 4 kcal mole-1 for the adsorption of oxygen on nickel oxide at 20°C. The agreement with the value (60 2 kcal mole-1) in Fig. 19 is remarkably good, particularly if it is considered that very different methods were used for the preparation of the nickel-oxide samples (19, 74)-... 

The presence of iron in nickel oxyhydroxide electrodes has been found to reduce considerably the overpotential for oxygen evolution in alkaline media associated with the otherwise iron free material.(10) An in situ Mossbauer study of a composite Ni/Fe oxyhydroxide was undertaken in order to gain insight into the nature of the species responsible for the electrocatalytic activity.(IT) This specific system appeared particularly interesting as it offered a unique opportunity for determining whether redox reactions involving the host lattice sites can alter the structural and/or electronic characteristics of other species present in the material. 

In a promising development of oxygen determination, Kirsten [106] carried out the pyrolytic determination of oxygen in organic compounds at 1020°C with the use of amorphous carbon containing 20% of nickel. An important feature of the method is the addition of chlorohydrocarbon vapour to the flow of carrier gas. Kirsten [106] found that the reactor, i.e., the quartz tube, is rapidly rendered inoperative if the temperature is increased above 1020°C. To obtain quantitative results, it is sufficient to evaporate 1-chloropentane at a rate of 18ql/h. At present the Kirsten method is applied to Carlo Erba instrumentation. 

The quantitative conversion of combined oxygen into carbon monoxide on charcoal is used extensively in the trace determination of oxygen in organic compounds [118, 119]. When this method is implemented in practice, it becomes important to maintain the right reaction conditions (type of charcoal, temperature, etc.). For the quantitative conversion of oxygen into carbon monoxide it is recommended that anthracene black is used [120], and to suppress side-reactions between the anthracene black and the walls of the quartz tube it is advisable to use platinized anthracene black at 900°C [121]. The method was developed taking due account of the conditions of the quantitative conversion of carbon monoxide on a nickel catalyst in a flow of hydrogen, which were discussed elsewhere [22,114,115]. 

A DME has also been used for the amperometric determination of oxygen in river water and effluent samples. This involves the application of a constant potential of —1.5V versus the SCE. This approach has been found to be useful in eliminating interferences from cyanide and sulfide, as well as correcting for contributions from metal ions, such as iron, copper, zinc, and nickel. The method can be reliably used for oxygen determination when present within the concentration range of 0-15 mg 1 . ... 

Neither copper nor nickel powder electrodes are sensitive to the presence of oxygen in the system. In a similar way as for the nickel electrode, we determined the normal potential of a copper powder electrode using deactivated copper powder, that is to say, a powder deprived of places of higher state of energy on its surface. Such a powder is, for example, the one obtained by means of electrolysis. 

Determination of oxygen. The sample is weighed into a silver container which has been solvent-washed, dried at 400 °C and kept in a closed container to avoid oxidation. It is dropped into a reactor heated at 1060 °C, quantitative conversion of oxygen to carbon monoxide being achieved by a layer of nickel-coated carbon (see Note). The pyrolysis gases then flow into the chromatographic column (1 m long) of molecular sieves (5 x 10-8 cm) heated at 100 °C the CO is separated from N2, CH4, and H2, and is measured by a thermal conductivity detector. 

The surface and size of the metal particles after reduction were determined by gas chromatographic impulse titration in a flow system—for the platinum samples hydrogen-oxygen titration in nitrogen (7) was used, whereas chemisorption of oxygen in helium flow (8) was used for the nickel samples. Some samples were analyzed by electron microscopic examinations described in Ref. 9. 

---