Fuchs found phenomena that when high voltage is applied to deionized water filled in two contacted beakers, a floating water bridge forms
spontaneously. In this paper, we examined flow direction of water bridge and what effects the addition of electrolytes such as NaCl, NaOH, and
A lot of experiments on water have been reported since the ancient time. Water is a familiar substance and has many interested features. Dipole moment is one of them. Floating water bridge seems to be caused with it. It can be easily reproduced if you have a high voltage electric generator and deionized water.
First the top of two beakers filled with deionized water was in contact with each other, and then they were setting apart gradually under high voltage. Then spanning a bridge of water could be observed between top of two beakers. This experiment was reported by Fuchs [
We believe that the phenomenon was caused by electrical dipole moment of H2O molecular. So the addition of an electrolyte will disturb the aligned structure, and length of water bridge will be expected to be decreased with the concentration of electrolyte. In this paper, we would like to know the flow and the effects of adding electrolytes to deionized water on the length of water bridge.
Figure
Main part of apparatus.
First, both beakers were in contact with each other. Next, applying voltage to electrode, a beaker of anode side was moved away slowly. Finally, floating water bridge could be observed between both beakers like Figure
Floating water bridge.
We cannot obtain water bridge spontaneously. But we can observe it easily when high voltage is applied. High voltage arranges water molecules in a line of positive and negative polarity by turns like a rope. One cm long water bridge may bundle many water ropes which are composed of arranged more than hundreds of millions of water molecules. Because water molecules were attracted by the gradient of electricity, water flows from a beaker to the other. Once a rope decays with produced heat, it almost falls down. However it comes back again as polarity pulls back a rope. It is a surprising view. After several decays, finally produced heat as you can see in the figure breaks a rope and finished spanning the bridge. Streamer was also observed between two beakers after water bridge finished spanning.
Flow direction of water bridge could not be visually confirmed. To know the flow direction, water soluble electrolyte of NaCl was added in a beaker and the other deionized water. Distance between two beakers was kept 1 mm long, and high voltage to the beakers was applied less than 25 seconds. After a run, electric conductivity of deionized-water side solution was measured with an electrical conductance meter.
Figure
Change of electrical conductivity of cathode side solution when NaCl was added to the anode side solution.
Change of electrical conductivity of anode side solution when NaCl was added to the cathode side solution.
Figures
Assuming that floating water bridge is caused with dipole moment adding electrolytes will prevent forming floating water bridge. We chose soluble electrolytes in water as NaCl and NaOH, NH4Cl whose electrical conductivities were changed from 0 to 40
Effect of electrical conductivity of soluble electrolytes on length of water bridge:
Figure
Effect of concentrations of soluble electrolytes on length of water bridge:
We tried to add insoluble electrolyte Al2O3. Figure
Effect of Al2Ol3 on length of water bridge.
An experimental study on reduction of length of water bridge caused by added electrolytes was carried out.
Flow of the water bridge was observed in the experiment. The direction of flow was from the cathode side to anode side when the electrodes were applied 12 kV.
Adding soluble electrolytes, NaCl, NaOH and NH4Cl decreased the length of water bridge. Experimental results suggest that ionization degree of electrolyte affects decreasing water bridge length.
Addition of insoluble electrolyte Al2O3 to water gave little effects on the length of water bridge.
The authors wish to thank Mr. M. Usui who assisted with experiments.