Science, Tech, Math › Science What Does pH Stand For? Share Flipboard Email Print Difydave / Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated May 03, 2019 Have you ever wondered what pH stands for or where the term originated? Here is the answer to the question and a look at the history of the pH scale. Key Takeaways: Origin of pH Term pH stands for "power of hydrogen." The "H" is capitalized because it is the hydrogen element symbol. pH is a measure of how acidic or basic an aqueous solution is. It is calculated as the negative logarithm of hydrogen ion concentration. pH Definition and Origin pH is the negative log of hydrogen ion concentration in a water-based solution. The term "pH" was first described by Danish biochemist Søren Peter Lauritz Sørensen in 1909. pH is an abbreviation for "power of hydrogen" where "p" is short for the German word for power, potenz and H is the element symbol for hydrogen. The H is capitalized because it is standard to capitalize element symbols. The abbreviation also works in French, with pouvoir hydrogen translating as "the power of hydrogen". Logarithmic Scale The pH scale is a logarithmic scale that usually runs from 1 to 14. Each whole pH value below 7 (the pH of pure water) is ten times more acidic than the higher value and each whole pH value above 7 is ten times less acidic than the one below it. For example, a pH of 3 is ten times more acidic than a pH of 4 and 100 times (10 times 10) more acidic than a pH value of 5. So, a strong acid may have a pH of 1-2, while a strong base may have a pH of 13-14. A pH near 7 is considered to be neutral. Equation for pH pH is the logarithm of the hydrogen ion concentration of an aqueous (water-based) solution: pH = -log[H+] log is the base 10 logarithm and [H+] is hydrogen ion concentration in the units moles per liter It's important to keep in mind a solution must be aqueous to have a pH. You cannot, for example, calculation pH of vegetable oil or pure ethanol. What Is the pH of Stomach Acid? | Can You Have Negative pH? Sources Bates, Roger G. (1973). Determination of pH: Theory and Practice. Wiley. Covington, A. K.; Bates, R. G.; Durst, R. A. (1985). "Definitions of pH scales, standard reference values, measurement of pH, and related terminology" (PDF). Pure Appl. Chem. 57 (3): 531–542. doi:10.1351/pac198557030531 Cite this Article Format mla apa chicago Your Citation Helmenstine, Anne Marie, Ph.D. "What Does pH Stand For?" ThoughtCo, Feb. 16, 2021, thoughtco.com/what-does-ph-stand-for-608888. Helmenstine, Anne Marie, Ph.D. (2021, February 16). What Does pH Stand For? Retrieved from https://www.thoughtco.com/what-does-ph-stand-for-608888 Helmenstine, Anne Marie, Ph.D. "What Does pH Stand For?" ThoughtCo. https://www.thoughtco.com/what-does-ph-stand-for-608888 (accessed June 13, 2021). copy citation Watch Now: What are the Differences Between Acids and Bases?