Determination of the composition, stability constants and activation parameters of UO22+ - hexamethylenetetramine complexes at dropping mercury electrode

Polarographic reduction of complexation reactions of hexamethylenetetramine (HMTA) with uranyl ion in 1.0M KOAc at dme studied was found to be reversible and diffusion-controlled involving one electron transfer, the slope of log i/isub(d)-i vs E plot being 60 +- 2mV. The effect of pH on the complex formation was studied and pH 4.5 was selected for the study of the present system. Stability constants of the complexes were determined by DeFord and Hume method at different temperatures (25, 30 and 35deg) and the activation parameters were also calculated. The mono-dentate HMTA forms tetra co-ordinated complex with UO22+ ion and the stability constants for different species existing in solution UO2L2+, UO2L22+, UO2L32+ and UO2L42+ were calculated. The negative of the stability constants for UO2L32+ indicates that this species is not existing or highly unstable in solution. The plot of percentage distribution of metal ion present in the form of various species at 25deg has also been reported