Freshening up Old Methods for New Students: A Colorful Laboratory Experiment to Measure the Formation Constants of Ni(II) Complexes Containing Ethane-1,2-Diamine

This is an easy and inexpensive laboratory
experiment in which
undergraduate students at the Bachelor’s degree level in Chemistry
can measure formation constants of complexes [Ni­(en)n(OH2)6–2n]2+ (n = 1, 2 or 3; en = ethylenediamine) through
an acid–base titration. The background information necessary
to understand the activity involves familiarity with equilibria and
basic coordination chemistry, and the lab experience uses only common
glassware and a pH meter. The mathematical treatment of the results
is based on Bjerrum’s formation function. Details of the activity,
including full procedural and experimental data, are provided. The
experiment can be augmented with additional work based on Job’s
method to analyze the stoichiometry of the complexes under investigation.