Is this explanation correct?

by Dennis
(Amherst, MA, USA)

Regarding "The glass pH measuring electrode," the explanation states that H+ do not cross the membrane. Instead, it is asserted that Na+ cross. If so, then why does the electrode not measure Na+ instead of H+? Indeed, there are Na+ electrodes that are relatively specific for Na+, and they are not H+ electrodes.

How is it possible to measure pH in solutions that do not contain Na+?

If a current is passed through the membrane, according to the explanation Na+ migrate through. In an acid solution, H+ would migrate in, and eventually replace all of the mobile Na+. Then it would have to be H+ carrying the current.

I know of no reason not to accept a simpler explanation, which is that H+ do cross the glass membrane. What mechanism would allow Na+ to diffuse but not H+? Are there data consistent with the explanation? A reference is necessary.

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