【摘要】 <正> 光度法指示剂类多元酸离解常数的测定,当各级离解态的光谱差别甚小,或光谱既有红移又有紫移时,往往不易获得准确的结果。常见的铬天青S即具有上述性质。我们以此为例,利用它在不同pH时吸收光谱先后出现的三个等色点,判明了它的反应历程,并据此拟定了一个测定离解常数的方法,获得的结果比较令人满意。实验仪器:日本岛津UV-240分光光度计;日本东亚HM-20E型酸度计。更多还原

【Abstract】 The determination of the stepwise dissociation constant of chromazurol S with classical potentiometry or photometry is difficult to obtain accurate resutls. The combination of photometry and potentiometry and utilization of the isosbestic point formed by a cluster of absorption curves originated from a series of various pH solutions have been described in this paper. The specific characteristic of the absorbance of chromazurol S is used to differentiate its reaction process. The new method is suitable for this kind of polyacid with satisfactory results.更多还原