Stability Constants of Cu2+, Ni2+ and Zn2+ -fulvic Acid Metal Complexes

Department of Applied Chemistry,

University College of Science and Technology, Calcutta

Received 28 July 1971; revised MSS received 24 March 1972

Log K values of fulvic acid metal complexes are evaluated at pH 4.0 and 5.5 by ion exchange Technique.

Log K values for Cu-F.A. complex changes for 2.57 to 3.93 with change in \({p}\)H from 4.0 To pH 5.5, however, the same value for Ni-F.A. complex are 3.19 at \({p}\)H 4.0 and 3.23 at \({p}\)H 5.5 which indicate that stabilities of Ni-F.A. complexes are not changed for change in \({p}\)H. The log K value for Zn-F.A. complex changes from 2.99 at \({p}\)H 4.0 to 4.16 at pH 5.5 The result of this investigation indicate that the log K values are not in accordance with Irving-Williams series and the following sequences Ni²⁺ > Zn²⁺ > Cu²⁺ at pH 4.0 and Zn²⁺ > Cu²⁺ > Ni²⁺ at \({p}\)H 5.5 are observed.