I acknowledge my limitations but isn't 'two aitches straddling a single o' spell 'HOH' rather than H2O

Hi Steve
I believe Norman is referring to the molecular construction rather than the letters i.e.
http://www.dichotomistic.com/images/water%202.gif

It's fine to write the molecular formula for water as HOH and some people do for mechanistic purposes. The subscript 2 is just a way of grouping like atoms. A proportion of the molecules in pure water at equilibrium will always be dissociated into the ions: H3O+ and OH-

I prefer the 'Dihydrogen Monoxide' convention myself. Lethal stuff.

: )

http://www.dhmo.org/facts.html

Jx