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通过对弱酸难溶盐平衡体系的讨论，导出了弱酸离解常数、金属离子浓度和溶液ｐＨ值之间的关系，从而给出一种利用金属离子选择电极测定弱酸离解常数的方法。采用该法，本文用钙离子选择电极对Ｈ２ＣＯ３、Ｈ２Ｃ２Ｏ４和ＨＦ的离解常数进行了测定，得到与文献值相一致的结果（Ｈ２ＣＯ３∶ｐＫ１＝６．５３，ｐＫ２＝１０．２５；Ｈ２Ｃ２Ｏ４∶ｐＫ１＝１．３２，ｐＫ２＝４．２４；ＨＦ∶ｐＫ＝３．０８）。同时本法还可以用来测定相应的溶度积常数。
The weak acid dissociation constant, the concentration of metal ions and the pH value of the solution were deduced through the discussion of the weak acid equilibrium system, and a method of determining the dissociation constant of weak acid by using metal ion selective electrode was given. In this paper, the dissociation constants of H2CO3, H2C2O4 and HF were determined by calcium ion selective electrode. The results were consistent with the literature values (H2CO3: pK1 = 6.53, pK2 = 10.25; H2C2O4: pK1 = 1.32, pK2 = 4.24; HF: pK = 3.08). At the same time this law can also be used to determine the corresponding solubility product constant.