The Meaning of pH

Acid WarningEveryone hears of pH and knows that a low pH is acidic, but what does pH mean? I mean, what do the letters pH stand for?

Someone in my lab broke a pH meter today. Other than the thought of “yikes, someone’s not going to be happy,” I also thought, “what the heck does pH stand for?” It’s technically the measure of the activity of the hydrogen ion, or more commonly referred to as the negative logarithm of the concentration of hydrogen ions, but the actual letters don’t correspond to either definition.

It turns out that the origin of the term pH is actually quite a mess. The concept of pH was first introduced in Denmark but no one is sure which language pH was coined in. The term pH stands for “potential Hydrogen” in English and “pondus hydrogenii” in Latin.

[Photo Credit] bradleygee

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