# What does "pH" stand for? **URL:** \ **Category:** Factual Questions\ **Created:** [August 5, 2023, 1:50am UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085 "2023-08-05T01:50:30Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [August 5, 2023, 1:50am UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/1 "2023-08-05T01:50:30Z")
When it comes to terms in chemistry, what does “pH” stand for? ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [August 5, 2023, 1:55am UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/2 "2023-08-05T01:55:59Z")
potential of hydrogen ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [August 5, 2023, 1:57am UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/3 "2023-08-05T01:57:22Z")
Thank you. ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [August 5, 2023, 2:04am UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/4 "2023-08-05T02:04:32Z")
Your welcome ---
**Author:** ![penultima\_thule](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/penultima_thule/32/3833_2.png) [@penultima\_thule](https://boards.straightdope.com/u/penultima_thule)\ **Post date:** [August 5, 2023, 2:27am UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/5 "2023-08-05T02:27:48Z")
pH is calculated as the power (base10) of H+ concentration so in my chemistry education we used the term “power” of hydrogen ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [August 5, 2023, 5:27am UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/6 "2023-08-05T05:27:02Z")
pH represents the negative of the base-10 logarithm of the concentration of hydrogen ions. The “p” itself, though, is thought not to have represented any word in particular in the original source material (which, for instance, also used “q” in a similar fashion). In the years since its origin, people have back-applied meanings like “power” and “potential”. ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [August 5, 2023, 11:20am UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/7 "2023-08-05T11:20:29Z")
Wikipedia: > Sørensen did not explain why he used the letter p, and the exact meaning of the letter is still disputed.[[6]](https://en.m.wikipedia.org/wiki/PH#cite_note-6) Sørensen described a way of measuring pH using _potential_ differences, and it represents the negative _power_ of 10 in the concentration of hydrogen ions. The letter _p_ could stand for the French _puissance,_ German _Potenz,_ or Danish _potens_, all meaning “power”, or it could mean “potential”. All of these words start with the letter _p_ in [French](https://en.m.wikipedia.org/wiki/French_language), [German](https://en.m.wikipedia.org/wiki/German_language), and [Danish](https://en.m.wikipedia.org/wiki/Danish_language), which were the languages in which Sørensen published: Carlsberg Laboratory was French-speaking; German was the dominant language of scientific publishing; Sørensen was Danish. He also used the letter _q_ in much the same way elsewhere in the paper, and he might have arbitrarily labelled the test solution “p” and the reference solution “q”; these letters are often paired.[[7]](https://en.m.wikipedia.org/wiki/PH#cite_note-7) Some literature sources suggest that “pH” stands for the [Latin term](https://en.m.wikipedia.org/wiki/Latin_language) _pondus hydrogenii_ (quantity of hydrogen) or _potentia hydrogenii_ (power of hydrogen), although this is not supported by Sørensen’s writings.[[8]](https://en.m.wikipedia.org/wiki/PH#cite_note-Otterson2-8)[[9]](https://en.m.wikipedia.org/wiki/PH#cite_note-Lian2-9)[[10]](https://en.m.wikipedia.org/wiki/PH#cite_note-Bradley2-10) > In modern [chemistry](https://en.m.wikipedia.org/wiki/Chemistry), the p stands for “the negative [decimal logarithm of](https://en.m.wikipedia.org/wiki/Common_logarithm)”, and is used in the term p_K_a for [acid dissociation constants](https://en.m.wikipedia.org/wiki/Acid_dissociation_constant),[[11]](https://en.m.wikipedia.org/wiki/PH#cite_note-Jens2-11) so pH is “the negative [decimal logarithm of](https://en.m.wikipedia.org/wiki/Common_logarithm) H+ ion concentration”, while pOH is “the negative decimal logarithm of OH- ion concentration”. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 5, 2023, 1:51pm UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/8 "2023-08-05T13:51:16Z")
I always figured it was “proportion”, because it’s a (representation of a) ratio. ---
**Author:** ![BobLibDem](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/boblibdem/32/3149_2.png) [@BobLibDem](https://boards.straightdope.com/u/BobLibDem)\ **Post date:** [August 5, 2023, 1:52pm UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/9 "2023-08-05T13:52:00Z")
I was taught power of hydronium. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [August 5, 2023, 2:23pm UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/10 "2023-08-05T14:23:32Z")
I was taught the p stood for ‘puissance’ (and the H for ‘hydrogen’). My freshman chemistry professor was quite definitive about that. He even said “too many fools think the p stands for ‘power’. But it stands for ‘puissance’, which is french for power”. Thanks, Dr. Robinson! ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [August 5, 2023, 2:35pm UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/11 "2023-08-05T14:35:16Z")
Side-bar: “Puissance du Canada” was the French version of “Dominion of Canada”. ---
**Author:** ![Mops](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mops/32/16494_2.png) [@Mops](https://boards.straightdope.com/u/Mops)\ **Post date:** [August 6, 2023, 9:56am UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/12 "2023-08-06T09:56:40Z")
FWIW in German 9th grade chemistry class we got told it was _potentia hydrogenii_. ---
**Author:** ![John\_DiFool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_difool/32/19543_2.png) [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)\ **Post date:** [August 9, 2023, 2:28pm UTC](https://boards.straightdope.com/t/what-does-ph-stand-for/988085/13 "2023-08-09T14:28:28Z")
> [@What\_Exit](#): > > Your welcome My welcome _what_? [[Oops wrong thread](https://boards.straightdope.com/t/irrational-language-pet-peeves/988273) 🤪]