【摘要】 <正> 氟试剂（茜素氨羧配合剂,Alizarin Complexan,简称ALC）的离解平衡及吸收光谱变化比较复杂,用经典的电位法或光度法较难获得准确的结果,以致数据差距较大.我们研究了它在不同pH时的吸收光谱,然后在等色点波长以吸光度对pH作图,得到一组等色点摩尔比曲线,由此导出测定离解常数的新方法.方法涉及的试验和计算均较简单,结果比较令人满意. 实验仪器 UV-240分光光度计;pH S-2型酸度计. 试剂氟试剂（A.R.北京化工厂）提纯后,常法配制成1.0×10^-2mol·L^-1的微酸性溶液.更多还原

【Abstract】 It is difficult to determine accurately the dissociation constants of polyacid of indicators with more than three dissociable hydrogen atoms. For example, Alizarin complexan and Xylenol orange, their dissociation constants obtained by different authors do not conform to each other. We make an extensive study of the absorption spectra measured from a series solutions of Alizarin complexan at various pHs. Among them there are three isosbestic points appeared. As a result, at the wavelengths of isosbestic points, we obtained isosbestic point-mole ratio curves, from which a new method for calculating the dissociation constant was found. By means of which a satisfactory result for Alizarin complexan was obtained.更多还原