Is that correct to say that osmosis happens with water only (based on the definition below) or it can happen with other liquids as well?

I've read the following definition in a book called "BRS - physiology" (6th edition, p.5):

"Osmosis is the flow of water across a semipermeable membrane from a solution with low solute concentration to a solution with high solute concentration."


2 Answers 2


No, it is not correct because it happens with other liquids (solvents) also.

Taking Wikipedia's definition:

Osmosis is the spontaneous net movement of solvent molecules through a semi-permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides.

Only as extra information: osmosis occurs until chemical potentials of every substance on each side of the membrane are equal. As the substance cannot move through the membrane, the liquid (solvent) do.

According to the definition, the book isn't correct, because it says with water only, but take into account that in biology the solvent is always water. So, as an internal definition of biology (or physiology) maybe is not wrong.


I'm pretty sure by definition, osmosis refers to the diffusion of water across a semipermeable membrane along a concentration gradient (ie from where water is in high concentration to where it is in relatively lower concentration). Diffusion refers to the movement of any particular substance along a concentration gradient, not necessarily through a semipermeable membrane (but can be). So yes, it is correct to say that osmosis refers to a process that is specific to water.

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    $\begingroup$ IUPAC doesn't has a definition for osmosis itself but for whatever reason "reverse osmosis" is defined in the gold book as "Liquid-phase pressure-driven separation process in which applied transmembrane pressure causes selective movement of solvent against its osmotic pressure difference.". If reverse osmosis is defined with just solvent and not water, why should osmosis only include water? $\endgroup$
    – DSVA
    Jun 5, 2017 at 15:17
  • $\begingroup$ Biologists, physiologists, biochemists, etc. define it with water ONLY, but other disciplines (chemistry, physics, engineering, etc.) will include other solvents as well. So, it really depends on who your audience is. $\endgroup$
    – Dr. J.
    Jun 4, 2018 at 13:45
  • $\begingroup$ @Dr.J. Nonsense. Why on earth should they use a different definition? Just because their samples usually are water-based? $\endgroup$
    – Karl
    Oct 19, 2018 at 6:25

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