CLAY & HUMUS STUDIES
Clay-humus and oxide-humus complexes : Extensive studies have been done on complexes of montmorillonite, illite, kaolinite, hematite, goethite, gibbsite and boehmite with humic and fulvic acids.  New concepts have been proposed to understand the mechanism of bonding, the influence of crystal edges, layer charge, cations, etc. in clay-humus bonding. These concepts have been developed based on an in-depth study of crystal structures, chemical reactions and high precision analytical data. Details of sites and modes of interaction and the reasons for behavioural differences between the minerals have been deduced. It was shown how (a) charges are distributed at various surfaces of crystals, (b) coordinate bonding with a crystal surface is possible and (c) strengths of cation-bridged bonds vary with the crystal structure.

Dissolution of oxide coatings from clay minerals : The short-comings of the Mehra-Jackson (DCB) method have been investigated. An improved method has been proposed.

References :
1. Varadachari C and Ghosh K (2006) Development of computer generated structural models : Teaching aids in soil mineralogy. Clay Research 25 45-53.
2. Varadachari C, Goswami, G and Ghosh K (2006) Dissolution of iron oxides. Clay Research 25 1-22

Weathering of silicates by organics : Reaction of olivine, epidote, hornblende, tourmaline, biotite and microcline by organic acids were studied. It was observed that the position of an ion within the crystal, its polymeric nature, steric factors and ligand strength, together influence dissolution of ions from the minerals; surface etching, fragmentation, layer opening and new crystal growth was demonstrated.