Source: pioyi/ion-selective-electrodes/hydration-of-glass
= Hydration of Glass
Before using the glass electrode, one must assure that it is hydrated. During hydration, single charged cations that are loosely placed in the glass lattice are overwhelmingly exchanged by hydrogen cations.
$$
\ce{H^+ + Na^+Gl^- <=> Na^+ + H^+Gl^-}
$$