含三乙醇胺的镀锌溶液中氢氧化钠的分析

Datermination of Sodium Hydroxide in Zn-plating Bath Containing Triethanolamine

本文加氯化钡沉淀分离碳酸钠,用百里酚酞作指示剂,pH9.4-10.6用盐酸滴定含三乙醇胺的镀锌溶液中的氢氧化钠。试验表明,使用百里酚酞指示刺。镀锌溶液中的三乙醇胺不影响氢氧化钠的测定,分析结果是准确的,而依照传统的方法用酚酞作指示剂,pH8.3-10.0,部分三乙醇胺参与反应,影响氢氧化钠的测定,使结果偏高,并且误差较大。

The content of sodium hydroxide in Zn-plating bath containing triethanolamine was determined by HCl titration, barium chloride was added to precipitate and seperate sodium carbonate and thymolphthalein was used as indicator to make the end point pH in the range of 9.4-10.6. Tests showed that the determination result was accurate when thymol- phthalein was used as indicator, because triethanolamine would give no influences on the determination at that pH. However, by conventional methods, where phenol phthalein was used as indicator and end point pH value was 8.3—10.0. At that pH value, triethanolamine would take part in the reaction and bring effects on the determination of sodium hydroxide, so that the analysis data would become higher and the error greater.