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Pressure [Pa = J·m-3] is the concentration of the force at the point of action. More generally, pressure is the force times concentration at the interphase of interaction.

In addition to mechanical pressure, hydrostatic pressure, barometric pressure, gas pressure (oxygen pressure), isomorphic pressures are distinguished as osmotic pressure, diffusion pressure, reaction pressure, and even electric pressure. In ergodynamics, the pressure in a transformation, ΔtrΠ, is the product of free activity times force, ΔtrΠ = αtr·ΔtrF [mol·m-3 · J·mol-1 = J·m-3 = Pa].

In the classical physicochemical literature, there is confusion between the terms force and pressure: "This force is called the pressure of the gas" by Maxwell (1867); "This pressure is osmotic pressure. .. Osmotic forces are in fact .." by van't Hoff 1901; "Pressure-forces" by Einstein (1905); presentation of Fick's law of diffusion (which represents a flux-pressure relationship) as a flux-force relationship by Prigogine (1967).

Abbreviation: P, p, Π [Pa]

Reference: Gnaiger 1989 Energy Transformations; Gnaiger 2017 MiP2017

Comunicated by Erich Gnaiger 2018-09-16
  • The prevailing hypothesis of light at the time was that of Descartes. He believed that light was a 'pressure' transmitted through the transparent medium of the ether. Sight, he claimed, was due to this pressure impinging upon the optic nerve. - (White 1997: p 58-59)
  • In both the "Hypothesis" of 1675 and the student notebook of 1661-65, Newton tended to attribute gravity to the pressure of a descending aetherial shower. - (Dobbs 1975: p 210)


  • Dobbs BJT (1975) The foundations of Newton's alchemy or "The hunting of the Greene Lyon". Reissued as a paperback 1983. Cambridge Univ Press Cambridge:300 pp. - »Bioblast link«
  • White M (1997) Isaak Newton. The last sorcerer. Fourth Estate, London 402 pp. - »Bioblast link«
  • Maxwell JC ( 1867) On the dynamical theory of gases. Phil Trans Royal Soc London 157:49-88. - »Bioblast link«
  • van't Hoff JH (1901) Osmotic pressure and chemical equilibrium. Nobel Lecture December 13, 1901. - »Bioblast link«
  • Einstein A (1905) Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen. Ann Physik 4, XVII:549-60. - »Bioblast link«
  • Prigogine I (1967) Introduction to thermodynamics of irreversible processes. Interscience New York, 3rd ed:147pp. - »Bioblast link«
  • Mitchell P (1966) Chemiosmotic coupling in oxidative and photosynthetic phosphorylation. Biochim Biophys Acta Bioenergetics 1807 (2011):1507-38. - »Bioblast link«
  • Gnaiger E (1989) Mitochondrial respiratory control: energetics, kinetics and efficiency. In: Energy transformations in cells and organisms. Wieser W, Gnaiger E (eds), Thieme, Stuttgart:6-17. - »Bioblast link: introducing chemical reaction pressure«

MitoPedia concepts: MiP concept, Ergodynamics