Abstract
An extraction-photometric method for the determination of cobalt in zirconium and its alloys with 1-nitroso-2-naphthol {T. Sawada and S. Kato, Sumitomo Light Metal Technical Reports, 5, 302 (1964)} was applied to the analysis of nickel- and iron-base alloys which could be used in a high temperature gas cooled reactor.
The amount of 1-nitroso-2-naphthol added must be increased six times as much as the amount used in the original work because nickel and iron consume the reagent. An oxidized product of the reagent which was sometimes obtained during the extraction, could be removed by shaking the extract with an alkaline solution containing hydroxylamine.
The following method (ε=3.5×104) was used for the determination of more than 0.01 % of cobalt in standard samples of high-temperature alloy which are being produced at Japan Atomic Energy Research Institute and for the determination of traces of cobalt in uranium.The method is also useful for analyzing aluminum, molybdenum, tungsten, niobium and titanium.
A nickel-and iron-base alloy(<0.5 g) is dissolved in an acid mixture(HCl : HNO3 : H2O=1:1:1). Metaland oxides of uranium (<3g) are dissolved in nitric acid. To a solution (Co<40μg), are added 25ml of 2 M citric acid and 15 ml of 2×10-2 M 1-nitroso-2-naphthol, and the pH of the solution is adjusted to 3 to 4 with 10 M sodium hydroxide. After addition of 10 ml of conc. hydrochloric acid, the cobalt complex is extracted In exactly 20ml of benzene by shaking vigorously for 1 min. The organic phase is successively washed with 20 ml each of conc. hydrochloric acid, water, 1 M sodium hydroxide and sodium hydroxide (1M)-hydroxylamine hydrochloride (0.5%) by shaking to remove other metals and the excess 1-nitroso-2-naphthol. The absorbance of the organic phase is measured at 410 nm.
