3-Nitroso-4-hydroxy-5,6-benzocoumarin (NHBC) as a reagent for the spectrophotometric determination of copper(II) in alloys

Abstract

Copper(II) forms in the pH range 6.3 to 7.8 a yellowish brown complex with 3-nitroso-4-hydroxy-5,6-benzocoumarin which is soluble in a 60 % dioxan medium giving a deep yellow coloured solution. Beer’s law is obeyed up to 2.80 ppm of copper(II) at 420 nm. The sensitivity of the colour reaction is 0.0032 μg Cu (II)/cm², for log I₀/I = 0.001 and the molar absorptivity is 1.98 × 10⁴ litre mole^-1 cm^-1. The composition of the complex is 1:2 as determined by Job’s and mole ratio methods. The colour reaction of copper(II) with NHBC has been made the basis for spectrophotometric determination of copper in alloys containing iron, zinc, nickel and copper.