针对连续变化法测定络合物稳定常数实验中可能出现的设计缺陷的讨论

Possible Flaw in Experiment Design on Continuous Variation Method for Determining the Stability Constant of a Complex

连续变化法测定络合物组成和稳定常数是大学化学中的经典学生实验。但针对1∶2和1∶3的络合反应,实验教科书的设计中可能出现数据点过少也就是溶液配制过少的问题。如果按照要求配制溶液,由于没有完全反应的混合溶液,而其他混合溶液给出的数据又都呈良好的线性,就缺少了用来估算曲线的数据点,结果是,将没有足够的数据对稳定常数进行估算。对这种可能出现的数据点过少的实验设计的原因、结果和解决方法进行了探讨。

Determination of the formula and stability constant of a complex by the continuous variation method is a standard experiment for chemistry students in universities. But when the metal to ligand complexation formation is 1 ： 2 or 1： 3, the experiment designs in all the experiment textbooks may have the same flaw, which is too few sampling points, or too few solutions being prepared. If the solutions were prepared according to these textbooks, there would be no solution with the metal to ligand ratio which corresponds to the stoichiometry of the complex. With all the points showing good linearity, there would not be enough data to estimate the curve so as to calculate the stability constant. This paper discussed the reason, consequences and solu tions of this flaw in this kind of experiment design.