CHARACTERIZATION OF AQUEOUS RUBIDIUM CHLORIDE AS AN EQUITRANSFERENT ULTRACONCENTRATED SALT BRIDGE

From e.m.f. measurements on the concentration cells Ag\AgCl\RbCl (m)pa rallel to RbCl (m(f))\AgCl\Ag and Rb-amalgam\RbCl (m(f))parallel to Rb Cl (m)Rb-amalgam, the ion and solvent transference numbers have been d etermined for aqueous RbCl solutions at molalities up to 7 mol kg(-1) over the temperature range from 25 to 55 degrees C. From the ionic tra nsference numbers found, aqueous RbCl emerges as the most closely equi transferent salt bridge ever characterized. Considering also its high solubility (7.8 mol kg(-1) at 25 degrees C), RbCl is recommended as a built-in salt bridge for reference electrodes, in view of replacing th e insufficiently equitransferent KCl bridges so far adopted by manufac turers.