Nicotinamidoxime as an analytical reagent

Summary Alkaline solutions of nicotinamidoxime containing traces of nickel(II) give a deep blue color on treatment with iodine. At a p_H of 10.5–11.5 in presence of an excess of the amidoxime the color develops almost instantaneously and is stable for at least 24 hrs. The system adheres to Beer's law in the range of 0.3–10 ppm of nickel, and the optimum range for measurement (1 cm cell) is 3–10 ppm of the metal. The color reaction is highly sensitive (spectrophotometric: 0.014 g Ni cm^–2 at 575 nm identification limit: 0.5 g Ni ml^–1; 12 · 10⁶).All the common anions are without any effect excepting CN^– and EDTA which interfere seriously. Interference of Pb²⁺, Bi³⁺, Al³⁺, Ti⁴⁺, Zr⁴⁺ and Th⁴⁺ can be masked by excess tartrate; while in the presence of Cu²⁺, Co²⁺, Zn²⁺, Mn²⁺ and Fe³⁺, the Ni²⁺ is first separated by the anion exchange method of Kraus and Moore ³ and then determined as usual.From the results of polarographic investigations it has been concluded that in alkaline medium nicotinamidoxime is first oxidized possibly to an azo type of compound which interacts with nickel(II) forming the deep blue color.Part II: K. K. Tripathi and D. Banarjea: Z. analyt. Chem. 168, 407 (1959).