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Encyclopedia of Astrobiology pp 1Cite as

pH

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Synonyms

Hydrogen ion concentration index

Definition

pH describes the activity of hydronium ions (H3O+, or more precisely the hydrated form of the proton H+ in solution) in aqueous solution. pH characterizes the acidity or basicity of aqueous solutions. It is formally defined by the relation:

$$ \mathrm{p}\mathrm{H}=-{ \log}_{10}{a}_{\mathrm{H}} $$

in which a H is the activity of the solvated hydronium ion. The pH of an acidic solution is less than 7, and the pH of basic solution is greater than 7 at 25 °C, but pH values change as a function of temperature.

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Authors and Affiliations

  1. Yokohama National University, Tokiwadai, Yokohama, 240-8501, Japan

    Kensei Kobayashi

Authors
  1. Kensei Kobayashi
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Correspondence to Kensei Kobayashi .

Editor information

Editors and Affiliations

  1. Centro de Biología Molecular, Universidad Autónoma de Madrid, Madrid, Spain

    Ricardo Amils

  2. Labo. d'Astrophysique de Bordeaux (LAB), Observatoire Aquitain des Sciences de l'Univers (OASU), Floirac CX, France

    Muriel Gargaud

  3. Centro de Astrobiología (CAB), Inst. Nacional de Técnica Aeroespacial, Torrejón de Ardoz, Madrid, Spain

    José Cernicharo Quintanilla

  4. Geophysical Lab., Carnegie Institution of Washington, Washington, District of Columbia, USA

    Henderson James Cleaves

  5. Astronomy Department, University of Massachusetts, Amherst, Massachusetts, USA

    William M. Irvine

  6. Dépt. Sc. de la Terre et de l’Atmosphère, Université du Québec, Montréal, Montreal, Québec, Canada

    Daniele Pinti

  7. Centre National d'Etudes Spatiale (CNES) DPI/E2U, Paris CX, France

    Michel Viso

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© 2014 Springer-Verlag Berlin Heidelberg

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Kobayashi, K. (2014). pH. In: Amils, R., et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-27833-4_1176-5

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  • DOI: https://doi.org/10.1007/978-3-642-27833-4_1176-5

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  • Publisher Name: Springer, Berlin, Heidelberg

  • Online ISBN: 978-3-642-27833-4

  • eBook Packages: Springer Reference Physics and AstronomyReference Module Physical and Materials ScienceReference Module Chemistry, Materials and Physics

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