ON THE THERMODYNAMIC ACTIVITIES OF IONS IN AQUEOUS-SOLUTIONS OF ELECTROLYTES

A strong electrolyte in a dilute aqueous solution of concentration m, completely dissociates into its ions, each individual ion having a con centration m, and each carrying a charge depending on its valency. The thermodynamic activity of each ion will depend on the charge it carri es and on m, multiplied by a factor gamma termed activity coefficient, to allow for the apparent reduction in concentration caused by mutual ly interacting different ionic species in the solution. Thus, the acti vity of an ion in a solution of m may be re-defined as the 'effective strength' of the ion and expressed by the term z2 x mgamma, where z is the valency of the ion. It is not the 'effective concentration' or my as it is now defined and generally assumed to be. Experimental data a re presented to confirm this new definition. A reference electrode wit hout liquid junction has been devised to measure single ion activities , using a solid ion-transmitting conductor of silver-chloride rod, whi ch functions as a bridge between the reference and test cells.