电位滴定法测定锰酸钾湿品中锰酸钾和游离氢氧化钾的含量

Determination of potassium manganate and free potassium hydroxide in wet potassium manganate by potentiometric titration

建立了电位滴定法测定锰酸钾湿品中锰酸钾和游离氢氧化钾含量的方法。以硫代硫酸钠为滴定剂,采用氧化还原滴定法测定锰酸钾湿品中锰酸钾的含量;加入过量硫酸使锰酸钾完全歧化生成氢氧化钾,以pH电极为测量电极,用氢氧化钠标准溶液返滴定过量的硫酸,计算氢氧化钾的总量;根据氧化还原滴定法测得的锰酸钾的含量计算锰酸钾歧化反应生成的氢氧化钾的含量,间接计算游离氢氧化钾的含量。结果表明,锰酸钾含量测定的平均加标回收率为99.9%,RSD=0.3%(n=9);游离氢氧化钾含量测定的平均加标回收率为100.6%,RSD=0.6%(n=9),准确度和精密度较好。该方法操作简单,结果准确,可用于锰酸钾湿品的质量控制。

Methods for the determination of potassium manganate and free potassium hydroxide in wet potassium manganate by potentiometric titration were established.The content of potassium manganite was determined by redox titration with sodium thiosulfate as titrant.Excessive sulfuric acid was added to completely disproportionate potassium manganate to potassium hydroxide.The pH electrode was used as the measuring electrode,and the excess sulfuric acid was back titrated with sodium hydroxide standard solution to calculate the total amount of potassium hydroxide.The content of potassium hydroxide produced by the disproportionation reaction of potassium manganate was calculated according to the content of potassium manganate measured by redox titration,and the content of free potassium hydroxide was indirectly calculated.The results showed that the average recovery of potassium manganate was 99.9%,RSD=0.3%(n=9),and the average recovery of free potassium hydroxide was 100.6%,RSD=0.6%(n=9).The two methods all have good accuracies and precisions.The methods are simple,accurate,and are suitable for quality control of potassium manganate wet products.