Characterization of metal complexes with humic fractions by potentiometric titrations

Abstract

The present study was carried out at the laboratory, Department of Soil Science and Agricultural Chemistry, College of Agriculture, Rajendranagar to characterize the complex formation of humic fractions with metal ions. The results observed that increase in pH of humic and fulvic acid when titrated with 0.1 N NaOH indicates higher buffering capacity of these fractions. Potentiometric titration curves obtained for both humic and fulvic acids are sigmoidal in shape indicating their weak acid nature. Absence of inflection indicates the formation of metal complexes. Among the metal -humate and metal -fulvates Fe does not show any inflection with both humic and fulvic acid indicating Fe metal ion forms more stable complexes with these fractions. Thus these humic substances can be used as carrier materials especially supply of micronutrients in crop nutrition as these also prevents the loss of nutrients from leaching by forming complex with metal ions like cationic micro nutrients.