许多资料介绍用溴氧化法对加碘食盐(简称碘盐)中的碘进行定量测定,但在实践中我们发现这个方法有时会出现异常现象。例如,我们曾用一磷酸(广州化学试剂厂产品,化学纯、批号710214)测定20多份经定性检验为阳性的碘盐,在溴氧化过程中,溶液不断退色,补加饱和溴水约4ml,放置约1小时,均未能检出碘;用分析纯氯化钠加碘化钾标准液作回收试验,也未能检出碘;使用与该批号相同的三瓶磷酸作试验,情况都是如此。又曾使用一磷酸(广州化学试剂厂产品,分析纯,批号不清)作回收试验(用分析纯氯化钠加碘化钾作回收)。14次试验回收率平均为89.9％,结果显然偏低。据此推断,是由于磷酸中可能存在的还原性物质对测定有干扰。但近期有资料报道用溴氧化法测定碘盐中碘所得结果异常的情况,认为是盐样中存在干扰物质。鉴于这种情况,我们对溴氧化法进行了改进:在弱的硫 Many sources describe the quantitative determination of iodine in iodized salt using bromine oxidation, but in practice we find that this method can sometimes be anomalous. For example, we used a monophosphate (Guangzhou Chemical Reagent Factory product, pure chemical, lot number 710214) measured more than 20 qualitatively tested positive iodized salt, the bromine oxidation process, the solution continued to fade, add about 4ml of saturated bromine water , For about 1 hour, were unable to detect iodine; with analytical sodium chloride plus potassium iodide standard solution for recovery test, also failed to detect iodine; using the same batch of three bottles of phosphoric acid for the test, the situation is so. Also used a monophosphate (Guangzhou Chemical Reagent Factory products, analytical grade, batch number is not clear) for the recovery test (with analytical sodium chloride plus potassium iodide recovery). The average recovery of 14 experiments was 89.9%, the result was apparently low. It is inferred from this that the determination is caused by the presence of reducing substances in phosphoric acid. However, there are recent data reported by the bromine oxidation method for determination of iodine salt in the results of the abnormal situation that there is interference in the salt sample. In view of this situation, we have made improvements to the bromine oxidation method: on weak sulfur