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氨三乙酸-氯化铵镀锌溶液主要成分为二氯化铵、硼酸、氨三乙酸、硫脲和氯化锌等。目前测定氯化铵一般采用甲醛酸碱滴定法和银量法,前法由于较多量锌的存在影响滴定终点;后法由于镀液中加入的锌的形式(有以氧化锌和氯化锌同时加入的)不同,在间接测定氯化铵时计算上发生困难。硼酸的测定采用甘露醇酸碱滴定法,由于大量Zn~(2+)和NH_4~+的存在严重影响滴定终点。氨三乙酸(NTA)的测定方法有以邻苯二酚紫为指示剂,用铋或铅盐溶液进行滴定;以钙试剂为指示剂,用钙盐溶液滴定;以铬天青S为指示剂,三氯化铁溶液滴定等方法。以铬天青S为指示剂的方法较好,但杂质铁的存在使结果偏低。
Ammonia triacetic acid - ammonium chloride The main components of zinc plating solution is ammonium chloride, boric acid, nitrilotriacetic acid, thiourea and zinc chloride. The current determination of ammonium chloride is generally used formaldehyde and alkali titration method and the amount of silver, the former method due to the presence of a larger amount of zinc titration end point; after the law due to the bath added to the form of zinc (with zinc oxide and zinc chloride at the same time Added), it is computationally difficult to measure ammonium chloride indirectly. The determination of boric acid by mannitol acid-base titration method, due to the presence of a large number of Zn ~ (2+) and NH 4 ~ + seriously affect the titration end point. Determination of nitrilotriacetic acid (NTA) with catecholamine violet as an indicator, with bismuth or lead salt solution titration; Calcium reagent as an indicator, titration with calcium salt solution; chrome azure S as an indicator , Ferric chloride solution titration and other methods. Chromium azurol S as an indicator of the method is better, but the presence of iron impurities so that the results are low.