Exchange Reactions of Mn²⁺, Co²⁺ and Ni²⁺ with Mg²⁺ as a Complementary Ion on a Montmorillonite Clay

H-M₁-clays and H-M₁-Mg-clays were prepared having different equivalents of M₁ and Mg and ‘release experiments’ were conducted using H₂SO₄ at symmetry concentration once (Release I) and six times (Release VI). The following sequences in adsorption of cations by H-clay: Mn²⁺>Ni²⁺=CO²⁺>Mg²⁺ and in release from clay-salts by H+: Mg²⁺>Mn²⁺> Ni²⁺=Co²⁺ were noticed. Calculated on the basis of 100% addition, ‘Release I’ increased with decrease of proportion of the above transitional metal cations suggesting more availability as ‘trace’ condition approached. On similar considerattion, both adsorption and ‘Release VI’ were independent of the ratios of the added cations. It was noticed that a portion of the transitional metal cations could not be desorbed, possibly due to ‘fixation’ by clay in its lattice.