Cr^(3+)的水解聚合作用(Ⅴ)——Cr^(3+)的第一和第二级水解常数

Hydrolytic Polymerization of Chromium(Ⅲ)Ion(Ⅴ)——The First and Second Hydrolysis Constants of Cr^(3+)

本文首先用量热滴定法证实,在一定的pH范围内,一级水解产物CrOH^(2+)可单独存在,而Cr(OH)+2则不能。进而在考虑单核和多核共存时,用曲线拟合法求出一级和二级水解常数lgβ_(11)=-4.15±O.04,lgβ_(21)=-8.40±0.03,并与前人的结果作了比较。

The chromium(Ⅲ)ion is of characteristic by hydrolysis reaction.Its second hydrolysis-product Cr(OH)^(2+)always coexists together with polynucl-ear species,but this complicated case was not takeninto account while determinating hydrolysis constant of Cr(OH)^(2+).Therefore the result obtained by previous authors is unsatisfactory.We proved first by calorimetric titration that the first hydrolysis product CrOH^(3+)can exist alone,but Cr(OH)^(2+)can not within certain range of pH value and furthermore obtained the first and second hydrolysis constants by curve-fitting under considering the coexistence of mono-and polynuclear species.The result is as follows:1gβ_(11)=-4.15±0.04,1gβ_(21)=-8.40±0.03.The comparision with the previous results has deen made.