MECHANISM OF THE MERCURY BEATING HEART - AN EXPERIMENTAL-STUDY OF THEELECTROCHEMICAL-MECHANICAL OSCILLATOR

Detailed mechanism of oscillation of the ''mercury beating heart'' was investigated for the iron-triggered and the aluminium-triggered cases by probing the electrode potential, electrocapillarity and the shape of the mercury surface. Electrochemical reductions primarily of dissol ved oxygen on the mercury surface and corrosion reactions of the activ e metals such as Fe or Al drove the potential of mercury alternately u p and down. The range of potential oscillation was found to be on the positive side of the electrocapillary maximum of mercury in the case o f Fe-triggered oscillation in acidic solutions, and on the negative si de in the case of Al-triggered oscillation in basic solutions. The ult imate cause of the mercury oscillation was shown to be fluctuating sur face charge density without involving a film-formation on the mercury surface or oxidation of mercury, at variance with some views in the li terature. Copyright (C) 1996 Elsevier Science Ltd