Polarography of the hydrogen ion in concentrated solutions of lithium chloride

Abstract

The addition of lithium chloride to an aqueous solution containing the hydrogen ion breaks down the hydrogen-bonded water structure. At 8 molal lithium chloride the hydrogen ion is no longer able to move by the ‘proton jump’ mechanism. The half-wave potential of hydrogen on mercury increases markedly between 4·5 and 13 molal. This effect is attributed to a decrease in the degree of hydration of the hydrogen ion, with a consequent increase in its activity. At concentrations greater than 13 molal the hydrogen ion is probably present as H₃O⁺ and the half-wave potential remains constant up to 19 molal (i.e., 3 moles of water per mole of lithium chloride). A further increase in half-wave potential occurs between 19 and 20 molal.