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(一)引言传统的确定酸碱滴定终点的方法一般有两类:一类是用指示剂;另一类是藉助于仪器,测定物理性能的突变,如电位滴定等。这二类方法都是根据pH-V滴定曲线的原理,从突跃部份找终点。但这些方法都有一定的局限性,例如:酸碱滴定,如果酸的pK值大于7,突跃不明显,就无法用指示剂确定终点位置。用电位滴定虽可用二级微商法算出终点,但如果ΔE/ΔV～V曲线图中曲线两侧不对称,则结果不准确(这和酸的电离常数有关,一般酸的pK值不大于8)。 (二)Ingman,Still和Johansson公式廿世纪五十年代初,有人倡议用直线法代替曲线法来求终点。其中有代表性的为Gran函数
(A) Introduction Traditional methods to determine the end of acid-base titration generally have two types: one is the use of indicator; the other is by means of instruments, determination of physical properties such as mutation, such as potentiometric titration. Both of these methods are based on the principle of the pH-V titration curve and find the end point from the jumps. However, these methods have some limitations, such as: acid-base titration, if the acid pK value is greater than 7, the jump is not obvious, you can not use the indicator to determine the end position. Although potentiometric titration can be used to calculate the end point of the second level of the micro-business method, but if the ΔE / ΔV ~ V curve on both sides of the curve asymmetry, the result is not accurate (which is related to the acid ionization constant, pK value of the general acid is not greater than 8 ). (II) Ingman, Still, and Johansson Formulas In the early 1950s, it was proposed to use the straight line method instead of the curve method to find the end point. Among them are Granular functions