The determination of formation constants of binary Lanthanone(III) complexes (ML), where M = Sm (III) or Eu (III) or Gd (III) or Tb (III) and L = 2-aminopyridine or 3-aminopyridine or 4-aminopyridine have been carried out using Irving - Rossotti titration technique in aqueous media at different temperatures and at ionic strength. To understand more about the nature of equilibrium involving lanthanide(III) complexes with aminopyridines the effect of dielectric constants on the stability of these complexes at different percentage of solvent variation and at different solvent systems has been studied.. The formation constant (logβn) have been calculated on IBM computer using BEST Program. The S min values are also calculated. Thermodynamic parameters (ΔG, ΔH & ΔS) are also evaluated, negative ΔG & ΔH values and positive ΔS values indicate that complex formation is favorable at ordinary temperatures. Species distribution curves of complexes have been plotted as function of pH using Fortran IV program SPE PLOT to visualize the equilibria systems in pH range of 2-12 pH. The metal ligand formation constant values of selected aminopyridine were in the order 4-aminopyridine > 2- aminopyridine > 3-aminopyridine. The order of stability for metals is Sm < Eu < Gd < Tb. These orders can be explained on the basis of basicity of ligand, protonation of ligand, electronic configuration of metal ions, size and ionic potential of tripositive ion, charge/size ratio of metal ions and species distribution diagrams. The mechanism through which protonation and complex formation takes place have been also discussed and shown by chemical reactions.

Speciation and thermodynamic parametric study on complexation behaviour of Sm(III), Eu(III), Gd(III) and Tb(III) with aminopyridines in aqueous and mixed equilibria

Chromates and Dichromates have been tested for its inhibitory effects towards tin coated steel in 0.5M monochloroacetic acid. The corrosion behaviour of potassium chromate, sodium chromate, potassium dichromate, sodium dichromate and ammonium dichromate was studied by polarization curves, Tafel parameters like Tafel slopes, extrapolation of cathodic Tafel line and intersection of cathodic and anodic line at open circuit potential in presence of inhibitors have been tabulated along with other electrochemical parameters and corrosion current have been calculated from Tafel lines. The efficiencies are calculated and compared reasonably well with those obtained from loss in weight data. All the inhibitors induce a significant increase of potential positive and direction accounts for cathodic polarization. The Icorr has also been calculated and that accounts well for cathodic reactions in presence of chromates and dichromates as inhibitors.

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Mahesh V. Kadia

Papers

Speciation and thermodynamic parametric study on complexation behaviour of Sm(III), Eu(III), Gd(III) and Tb(III) with aminopyridines in aqueous and mixed equilibria

Polarization Studies on Inhibitory Effect of Chromates and Dichromates on Corrosion of Tin Coated Steel in 0.5M Monochloroacetic Acid