铵盐无氰镀锌液中硼酸的测定,由于溶液中有大量的氯化铵,用通常的容量法,终点不能突变而无法观察,需分离去除铵盐。取试液5ml,加水50ml,20%氢氧化钠10ml,煮沸5分钟,除去氨,此时有白色沉淀出现,稍冷,滴加1:1盐酸,使沉淀溶解。加入约0.05M-EDTA20ml,冷却,加1滴甲基红指示剂,用0.25N氢氧化 Determination of boric acid in ammonium cyanide-free zinc plating solution, due to the large amount of ammonium chloride in the solution, can not be observed by the normal capacity method, the end point can not be mutated and the ammonium salt needs to be separated and removed. Take the test solution 5ml, add water 50ml, 20% sodium hydroxide 10ml, boil 5 minutes to remove ammonia, white precipitate appeared at this time, a little cold, dropping 1: 1 hydrochloric acid, the precipitate dissolved. Add about 0.05M-EDTA20ml, cooled, add 1 drop of methyl red indicator, with 0.25N hydroxide