用间苯三酚与氰基乙酸乙酯反应制备5,7-二羟基-4-亚氯基-2-氧基氧杂萘满。这种试剂在酸性介质中迅速与亚硝酸盐反应,其产物易于萃入正丁醇和乙酸乙酯的混合溶剂中且在361纳米具有吸收最大值。在0.005～0.280 ppm亚硝酸盐氮浓度范围内遵循比耳定律,表观摩尔吸光系数为2.25×10~4l·mol~(-1)·cm~(-1),对0.140ppm亚硝酸盐氮测定的相对标准偏差为±0.4％。此法应用于各种水试样中亚硝酸盐的分析,结果满意。 5,7-Dihydroxy-4-chloro-2-oxaquinazoline was prepared by the reaction of phloroglucinol and ethyl cyanoacetate. This reagent rapidly reacts with nitrite in an acidic medium and its product is easily extracted into a mixed solvent of n-butanol and ethyl acetate and has an absorption maximum at 361 nm. The Beer’s Law was obeyed at the concentration range of 0.005-0.280 ppm nitrite, the apparent molar absorptivity was 2.25 × 10 -4 l · mol -1 cm -1, and 0.140 ppm nitrite nitrogen The relative standard deviation of determination was ± 0.4%. This method is applied to the analysis of nitrite in various water samples with satisfactory results.