Microcalorimetric measurement of enthalpies of ion exchanges in aluminosilicate minerals and soils

An LKB 2107 batch microcalorimeter, fitted with a fully-automated injection device, was used to measure enthalpies of K-Ca exchange in aluminosilicate minerals and soils. The relationships between the differential enthalpies of K-Ca exchange, d( DELTA H//x)/dx, and cation saturation consisted of well-differentiated regions of constant d( DELTA H//x)/dx. These constant values were assigned to montmorillonitic, hydrous mica, mica and vermiculitic surfaces. On this basis, a muscovite mica examined was homogeneous, having only mica type surfaces, but a Fithian illite contained montmorillonitic, hydrous mica- and mica-type surfaces, and a Montana vermiculite, vermiculitic and montmorillonitic surfaces. Three out of four smectites contained mica-type surfaces. A new definition of 'true' montmorillonite is suggested.

RESP-09058