Mass and charge transfer within a floating water bridge

Abstract

When high voltage is applied to pure water filled into two beakers close to each other, a connection forms spontaneously, giving the impression of a floating water bridge 1-8 . This phenomenon is of special interest, since it comprises a number of phenomena currently tackled in modern water science. In this work, the charge and mass transfer through the water bridge are investigated with schlieren visualization and laser interferometry. It can be shown that the addition of a pH dye increases the H + and OH -production with subsequent electrolysis, whereas schlieren and interferometric methods reveal another mechanism where charge and mass transfer appear to be coupled. Whereas this mechanism seems to be responsible for the electrolysis-less charge and mass transfer in the water bridge, it is increasingly superseded by the electrochemical mechanism with rising conductivity. Thus it can be shown that a pH dye does only indirectly visualize the charge transfer in the water bridge since it is dragged along with the water flow like any other dye, and additionally promotes conventional electrochemical conduction mechanisms, thereby enhancing electrolysis and reducing the masscoupled charge transport and thus destabilizing the bridge.

Can a Century Old Experiment Reveal Hidden Properties of Water?

“…So far, this statement could not be verified; but a coupled bidirectional mass/charge transfer mechanism resulting in a lemniscate flow pattern has been reported [97] (see Figure 11). The nature of a possible charge carrier in this electrolysis-less system is compared to charged droplets in electrospray, where this issue is also still discussed [161].…”

“…In ref. [97] it is compared it to the charging in electrohydrodynamic atomization processes. However, in their excellent review about this topic, Gañán-Calvo and Montanero point out that "…the role played by the liquid polarity and the behavior of ionic species in the liquid are not satisfactorily described…" and that "… These issues still stir controversy (…) and require clarification.…”

“…Another interesting issue is that of charge and mass transfer [97]. Naturally, there are a number of theories explaining conduction and liquid motion in high voltage electric fields [98].…”

“…Meanwhile, more groups have picked up the topic, giving first results on ion transportation [94], Raman scattering [95] and a derivation of the Maxwell pressure tensor within the water bridge [96]. Next to that, an investigation of mass and charge transfer processes [97] has recently been presented.…”

“…The most thoroughly discussed electrochemistry hitherto is the addition of a pH dye to visualize the charge distribution in the system [92] as shown in Figure 15. In a recent paper [97] we further investigated the role of a pH indicator in this system, and found that one must be very careful when using it as charge visualization tool for the water bridge set-up, because the addition of a pH dye does not directly visualize charge. It raises the conductivity and induces electrochemical reactions.…”