I just learned about pH. If I understand it correctly, all it really tells is the concentration of positive hydrogen ions (protons) there are in a given liquid.
Why is this pH scale entirely dedicated to positive hydrogen ions? What is so special about protons/hydrogen ions? I would expect the scale to would count all positive ions, even if they are of atoms different from hydrogen. I don't understand why is the proton ion a "superstar", being so special that people made a scale dedicated just to it.