A radical steam-trap

Electrolysis is the neatest and most controllable of chemical reactions. Its applications are sadly limited by the problem of the electrodes. They are always attacked by discharging ions. Only in a few cases is this tolerable, or chemically useful. Daedalus now has a way out.

He points out that a smooth, red-hot heating element boils water very inefficiently. It becomes completely covered with a thin blanket of steam, through which heat leaks only slowly. Imagine, he says, such an element used as a electrode in an electrochemical cell. Its hot surface would emit electrons readily, like a valve cathode, and so should the hot water surface. Electrons travel quite well through water vapour (the special scanning electron microscope for wet specimens exploits this effect), though to aid their passage the system should be maintained at as low a pressure as possible. Two such electrodes would form an electrolytic cell. Most of its applied voltage would be dropped across the thin steam blankets around the electrodes, but this at least would help to keep them hot. Only a fraction of the voltage would go into electrochemistry; but that fraction would perform wonderful new reactions.

An ion discharged at a steam electrode will, as usual, be converted to the corresponding radical — often ferociously reactive and unstable. But deprived of the normal easy option of attacking the electrode, this radical will vent its energy on the molecules around it. Hydrogen ions will go to that energetic species, monatomic hydrogen. Metal ions will go to isolated metal atoms, hitherto available for chemistry only in the vapour phase. Azide will go to N₃, chlorate to ClO₃, hydroxide to OH — the most ruthlessly reactive of all radicals. All these will attack whatever target molecules the chemists have added to the solution; or failing that, the water itself. The results should be highly entertaining, and even useful. The vast new array of hitherto ignored or unknown radicals will make all sorts of splendid new syntheses possible.

But as a first step, Daedalus wants to use steam electrolysis to purify water. A few ferocious radicals should effortlessly degrade the few parts per billion of dioxin and halocarbons which make environmentalists faint with fear. All the nasties will be instantly mineralized, as the jargon has it. The most dubious piped product will be neatly converted into a chic mineral water.