应用氟离子选择性电极测定镀铬溶液中的氟硅酸

DETERMINATION OF FLUOROSILICIC ACID IN CHROMIUM PLATING BATH BY FLUORINE ION SELECTIVE ELECTRODE

本文提出了应用甘汞电极作参比电极,pF—1型氟离子选择电极作指示电极,以20％醋酸钠作离子强度缓冲剂,在pH5～6范围内,利用工作电池的电动势与F-活度(在10^(-2)～10^(-7)M之间)的对数成线性关系,用来测定镀铬溶液中的氟硅酸的含量。镀铬溶液中的铬酐浓度及可能有的杂质,Fe^(3+)、Cu^(2+)、Cl^-对测定均无影响,回收率可达到101％,与硝酸钍滴定法相比,本法简便、快速,又提高了测定的准确性。

It is recommended to use calomel electrode as reference electrode, PF-1 type fluorine ion selective electrode as indicator electrode, and 20% sodium acetate as buffering agent of ion strength at pH range of 5-6, to determine the concentration of fluorosilicic acid in chromium plating bath on basis of the linear relation between the electromotive force of working cell and the logarithms of F^- activity(10^(-2) -10^(-7)). The chromic anhydride content and the impurities possibly existing in chromium plating bath, such as Fe^(3+), Cu^(2+), Cl^- have little influence on the determination and the recovery rate can be up to 101%. It is simple, quicker and more accurate compared with the thorium nitrate titrimetric method.