Boric oxide dissolves in water to form boric acid. In the process,
it makes four strong covalent bonds to oxygen atoms to produce borate
ions, as described previously:
Because hydrogen ions are produced,
is an acidic oxide. Boric acid might better be written ,
to emphasize the proton that dissociates in water (center left).
Unfortunately, the usual practice is to leave out one water molecule
and write boric acid as ,
creating the erroneous impression that it is a hydroxide compound
and a base.
Boric acid is a very weak acid (see right). In aqueous solution,
most of the substance is found as undissociated boric acid molecules
and very little as borate ions, so the hydrogen ion contribution
by boric acid is small. Dilute boric acid solution is mild enough
to be used in eyewashes. (Don't try making your own. The results
could be dangerous.)