Eh–pH diagram

      any of a class of diagrams that illustrate the fields of stability of mineral or chemical species in terms of the activity of hydrogen ions (pH) and the activity of electrons (Eh). Consequently, the reactions illustrated on Eh–pH diagrams involve either proton transfer (e.g., hydrolysis) or electron transfer (oxidation or reduction) or both. In natural environments, pH values extend from 1 to 9.5, and Eh values from -500 to +800 millivolts. Rarely are temperatures and pressures other than those normally encountered on the Earth's surface considered.

      The area on an Eh–pH diagram that represents the range of these variables within which a particular mineral is stable is called the stability field of that mineral. Such a representation enables a geochemist to determine whether a mineral is in equilibrium with its surroundings or subject to chemical transformation. See also geochemical facies.

* * *


Universalium. 2010.

Look at other dictionaries:

  • Frost diagram — A Frost diagram is an Oxidation State Free Energy Diagram (O.S.F.E), also known as an Eh pH diagram, due to its axial labellings, and is used in electrochemistry to illustrate the relative stability of a number of different oxidation states of a… …   Wikipedia

  • Pourbaix diagram — In chemistry, a Pourbaix diagram, also known as a potential/pH diagram, maps out possible stable (equilibrium) phases of an aqueous electrochemical system. Predominant ion boundaries are represented by lines. As such a Pourbaix diagram can be… …   Wikipedia

  • Reduction potential — (also known as redox potential, oxidation / reduction potential, ORP or Eh) is a measure of the tendency of a chemical species to acquire electrons and thereby be reduced. Reduction potential is measured in volts (V), or millivolts (mV). Each… …   Wikipedia

  • Proper motion — The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system.[1] It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree.[2] This contrasts with… …   Wikipedia

  • Tenerife airport disaster — Tenerife disaster (KLM Flight 4805 and Pan Am Flight 1736) CGI rendering of KLM Flight 4805 immediately before it collided with Pan Am Flight 1736. Accident summary …   Wikipedia

  • Howard T. Odum — Infobox Systems scientist region = Systems Ecology era = 20th century color = #B0C4DE image caption = name = Howard Thomas Odum birth = 1 September 1924 Chapel Hill, North Carolina, USA death = 11 September 2002 Gainesville, Florida, USA school… …   Wikipedia

  • Sediment Profile Imagery — (SPI) is an underwater technique for photographing the interface between the seabed and the overlying water. The technique is used to measure or estimate biological, chemical, and physical processes occurring in the first few centimetres of… …   Wikipedia

  • List of nearest stars — Artist s conception of a red dwarf star, the most common type of star in the Sun s stellar neighborhood, and in the universe. Although termed a red dwarf, the surface temperature of this star would give it an orange hue when viewed from close… …   Wikipedia

  • Autism — This article is about the classic autistic disorder; some writers use the word autism when referring to the range of disorders on the autism spectrum or to the various pervasive developmental disorders.[1] Autism …   Wikipedia

  • HIV — Classification and external resources Diagram of HIV …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”