空气中的氯气经氢氧化钠溶液吸收后生成次氯酸钠,再经盐酸酸化释放出游离氯,游离氯能够定量地将碘化物氧化为单质碘,利用淀粉作为显色剂建立了间接分光光度法测定氯气的方法。反应体系的最大吸收峰位于570 nm处,氯的质量浓度在1.0 mg·L-1以内与吸光度之差ΔA呈线性关系,检出限(3s/k)为5×10-5mg·L-1。方法用于模拟气体和工厂附近空气样品分析。用标准加入法测得回收率在101%~103%之间,测定值的相对标准偏差(n=5)均小于2%。

Chlorine in air was absorbed with NaOH solution to form NaClO, which was reacted with HCl to release free chlorine. Iodide was quantitatively oxidized to I2 by Cl2 and reacted with starch to give a blue colored product, with absorption maximum at the wavelength of 570 nm. Linear relationship between values of ΔA and mass concentration of chlorine was kept in the range within 1.0 mg·L-1, with detection limit (3s/k) of 5×10-5mg·L-1. The proposed method was applied to the analysis of samples of simulated gas and air nearby the factory. Values of recovery found by standard addition method were in the ranges of 101%-103% with RSD′s less than 2%.