High-voltage and Water. Do you think water is a well-understood liquid? Not even close!

Well, if you apply enough voltage to anything, you’re guaranteed some kind of result, right?!

But lets be real: deionised water is a terrible conductor. So much so that it takes several kilovolts (kV) to see anything interesting. Above is typical pretty blue spark we get from about 1 kV, by connecting two small 100 ml beakers. Allowing the reaction to proceed with copper electrodes soon allows some nasty species to evolve:

Note the beautiful- but quite harmful - chlorine compounds arising from prolonged electrolysis at the cathode. Chlorine hypochlorite is the most likely species, a common ingredient in bleaches.

Here’s the fascinating result of connecting the two beakers by high voltage: water threading