在一系列体积相同的容量瓶中,加入一定量的金属离子 M 和一种配位体 R’(R’适当过量),以及浓度逐步增大的显色剂 R,并加入反应所必需的其它试剂,稀至刻度,摇匀。测量它们的吸光度,可得一系列吸光度 A_i。再用一个同一容量的容量瓶,加同样量的 M 和 R’,并加入过量的显色剂 R,使 M 最大限度地被 R 络合成 MRaR_b,此时所测吸光度为最大吸光度 A_(max)。根据络合平衡的原理,应有: In a series of equal volumetric flasks, add a certain amount of metal ion M and a ligand R ’(R’ appropriate excess), and a gradually increasing concentration of the developer R, and add other necessary Reagents, dilute to the mark, shake. Measurement of their absorbance, available a series of absorbance A_i. Then a volumetric flask with the same capacity, add the same amount of M and R ’, and add an excess of reagent R, so that M maximum synthesis of MRaR_b R, the measured absorbance at this time the maximum absorbance A_ (max ). According to the principle of complex balance, there should be: