用碘量法测定Fe~(3 )/Fe~(2 )体系中的游离酸

提出了一种滴定强酸性含Ｆｅ３＋及Ｆｅ２＋体系中游离酸（其游离酸浓度＞１ｍｏｌ／Ｌ）的新方法。实验证明，将Ｋ２Ｃ２Ｏ４作为掩蔽剂时，利用过量的ＫＩＯ３与过量的Ｎａ２Ｓ２Ｏ３在酸性溶液中的氧化还原反应可以测定体系中的游离酸。当体系中存在Ｆｅ２＋时，可利用ＫＭｎＯ４（在强酸性下）或Ｈ２Ｏ２（在弱酸性下）的预氧化来消除Ｆｅ２＋的干扰。在加入过量的Ｋ２Ｃ２Ｏ４（Ｃ２Ｏ４２－与Ｆｅ３＋的摩尔比值为３０）和过量的ＫＩＯ３及Ｎａ２Ｓ２Ｏ３的条件下，其化学反应可以在３０ｍｉｎ内完成。采用Ｉ２回滴法测定游离酸，测试结果的精密度高，测定结果的相对偏差小于３％

DETERMINATION OF FREE ACID IN A FERROUS AND FERRIC SOLUTION BY USING IODIMETRY

A new titrametry was developed to determine the free acidity of a strong acidic ferric or/and ferrous solution. The experiments show that the free acidity of a ferric or/and ferrous solution can be determined by a reaction of KIO 3 and Na 2S 2O 3, taking K 2C 2O 4 as a masking agent. The influence of ferrous solution can be eliminated by pre oxidation with the agent of KMnO 4 in strong acidity solution or H 2O 2 in weak acidity solution. Under the condition of adding over dose of K 2C 2O 4, KIO 3 and Na 2S 2O 3, the whole titration can be finished within 30 minutes. The average deviation of this method is 0.5% and the relative deviation is less 3%.