Forces between mica surfaces in aqueous KNO3 solution in the range 10–4–10–1 mol dm–3, showing long-range attraction at high electrolyte concentration

Abstract

Interactions between mica surfaces immersed in 10^–4–10^–1 mol dm^–3 aqueous KNO₃ have been measured: in contrast to earlier studies in this system, at the higher concentration range (> 4 × 10^–2mol dm^–3) the potential of the diffuse double-layer drops to values ψ_d < 30 mV. In 0.1 mol dm^–3 KNO₃ only attraction is observed down to the range of ‘hydration forces’(ca. 2 nm). The discrepancy with the earlier results is attributed to adsorption on the mica of surfactant originating in the Millipore filter used in our previous studies.