【Abstract】 The diazo-coupling reactions of congo red with 8-hydroxyquinoline were studied.This new colour system has a maximum absorbance wavelength at 512nm.Beer’s law was obeyed in the range of 0.02～0.8mg/L for NO^2-.The molar absorptivity was 3.1×10⁴L/mol·cm.The limit of quantitive determiation was 4.3×10^-3mg/L.The method was applied to the determination of nitrite in waste water with satisfactory results.更多还原