Charge storage in water
by tzvicky
An interesting discussion took place in the Langmuir recently. Ovchinnikova & Pollack have shown in experiment that water can macroscopically store electric charge, in other words, that a charge separation in water is possible for significant time periods – minutes, at least (Langmuir 2009, 25, 542). Then Corti & Collussi commented that such a storage would violate the principle of electroneutrality (Langmuir, 2009, 25, 6587). In a reply to this comment (Langmuir, 2009, DOI:10.1021/la901533c) O&P argue that although the principle of electroneutrality is taken as axiomatic, “exactly where this principle originated is unclear” and that its “violations can be found at levels ranging from the atomic to the cosmic. At the atomic level, electrons remain physically separated from the nucleus. At laboratory-scale levels, regions of water near hydrophilic surfaces contain long-lasting zones of separated charge”, in the atmosphere the intercloud charge separations couse 80% of lightning during thunderstorms. At the end O&E cite a classical water dropper experiment proposed by lord Kelvin (Wikipedia link) where two buckets of water can be oppositely charged. Then Corti & Collussi commented on O&P’s reply, however, they focus on water impurities and do not argue with the validity of the electroneutrality principle (Langmuir 2009, DOI:10.1021/la902030p).
A worth-seeing video from the water dropper experiment can can be seen in the last 6 minutes of the “MIT Open Courseware” lecture (link or see below).
