CATION-EXCHANGE MEASUREMENTS IN THE SOLID PHASE

Soils are capable of delivering nutrients or metal ions at a much lower moisture status than what is obtained in the pasty condition. Since exchange, if any, in the air-dry state will be very small, it has been studied by using radioactive gold ions, introduced as an exchangeable cation into the clay. The exchange of gold ion has been studied against Na- and Ca- clays by maintaining (i) one of the phases in the solid state and (ii) both the phases in the solid state. In (iii) exchange does take place but to a very small extent, whereas in (i) the exchange is quite appreciable.