Abstract
When a metal combines with an electron donor, the resulting substance is said to be a complex, or coordination compound. If the substance which combines with the metal ion contains two or more donor groups so that one or more rings are formed, the resulting structure is said to be a chelate. | The determination of equilibrium constants is of importance in the study of chelate compounds, since it is one promising approach to the accumulation of data which lead to a comprehensive understanding of chelates and the relationships which govern their formation and structure. There are several well known methods of calculating the equilibrium constant for complex formation: through pH measurements, described by Bjerrum; ion exchange, outlined by Schubert and Richter; methods based on Beer’s Law; oxidation potentials, described by Riley and Gallafent; and polarographic measurements, described by Lingane. | The formation constants of zinc(II)-glycine complexes have not been determined by the polarographic method, but have been determined from pH measurements at 250 C by Haley and Mellor, Bjerrum, Albert, and Monk. Ley has determined the formation constant of the zinc(II)-glycine conplex at 250 C from conductance measurements. It was of interest to extend the investigation of the zinc(II)-glycine system to higher glycine concentrations in order to determine whether the 1:3 complex exists and can be detected polarographically. It was also desirable to extend the investigation to temperatures other than 250 C to evaluate the several thermodynamic quantities associated with the complex formation reactions.