水质二氧化氯和亚氯酸盐的测定连续滴定碘量法2

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来源:本站发布时间：2018-10-16 18:31:36 浏览次数:4311次

1 适用范围

本标准规定了测定纺织染整工业废水中二氧化氯和亚氯酸盐的连续滴定碘量法。本标准适用于使用亚漂工艺的纺织染整工业排放废水中二氧化氯和亚氯酸盐的测定。当取样量为 150 ml时，二氧化氯的方法检出限为 0.09 mg/L，测定下限为 0.36 mg/L；亚氯酸盐（以亚氯酸根计）的方法检出限为 0.08 mg/L，测定下限为 0.32 mg/L。

2.方法原理

二氧化氯和亚氯酸根在不同 pH值条件下，能氧化碘离子而析出碘。同一个样品，在中性条件下，用硫代硫酸钠溶液滴定二氧化氯与碘离子反应转化为亚氯酸盐时析出的碘，再调节样品 pH值为1～3，用硫代硫酸钠溶液滴定亚氯酸盐与碘离子反应时析出的碘，通过连续滴定来测定二氧化氯和亚氯酸根含量。见反应式（1）和反应式（2）。

ClO2+I−→ClO2-+1/2I2 （1）

HClO2+4HI→2I2+HCl+2H2O （2）

3 干扰和消除

3.1 存在其它含氧氯化物，以及能与 I2 和I-发生氧化、还原反应的物质时，会产生干扰。

3.2 色度对滴定终点会产生干扰。水样有色度时，应取相同水样做为滴定终点判断的参比样品。

4 试剂和材料

除非另有说明，分析时均使用符合国家标准的分析纯化学试剂，实验用水为蒸馏水或去离子水。

4.1 碘化钾（KI）：晶体。

4.2 硫酸：ρ（H2SO4 ）=1.84 g/ml。

4.3 碘酸钾（KIO3 ）：优级纯。使用前，应于 105℃～110℃烘 2 h，置于干燥器内冷却至室温，备用。

4.4 氢氧化钠（NaOH）。

4.5 磷酸二氢钾（KH2PO4 ·2H2O）。

4.6 磷酸氢二钠（Na2HPO4 ·2H2O）。

4.7 硫代硫酸钠（Na2S2O3·5H2O）。

4.8 无水碳酸钠（Na2CO3 ）。

4.9 可溶性淀粉 [(C6H10O5 ) n ] 。

4.10 水杨酸（C7H6O3 ）。

4.11 氯化锌（ZnCl 2 ）。

4.12 硫酸溶液：1+1（v/v），用硫酸（4.2）配制。

4.13 氢氧化钠溶液：c（NaOH）=0.1 mol/L。

称取 4 g氢氧化钠（4.4）溶于少量水中，稀释至 1000 ml。

4.14 缓冲溶液：pH=7。

称取 34.0 g磷酸二氢钾（4.5）和 35.5 g磷酸氢二钠（4.6）于烧杯中，加水溶解后，稀释至 1000 ml。

4.15 碘酸钾标准溶液：c（1/6KIO3 ）=0.0500 mol/L。

称取 1.7835 g（精确至 0.0001 g）碘酸钾（4.3），用水溶解并定容至 1000 ml容量瓶，摇匀。贮存于棕色玻璃试剂瓶中，避光保存。

4.16 硫代硫酸钠标准溶液：c（Na2S2O3 ）≈0.05 mol/L。

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[86] => D:\wamp\chyc\data\ads\ad_1.php
[87] => D:\wamp\chyc\include\Ad.class.php
[88] => D:\wamp\chyc\data\front\runtime\templates_c\%%FD^FD7^FD7FB2B1%%footer.html.php
[89] => D:\wamp\chyc\include\tag\function.fflink.php

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