Term: hydrodynamically equivalent sphere
https://doi.org/10.1351/goldbook.H02896

Definition:
A hypothetical sphere, impenetrable to the surrounding medium, displaying in a hydrodynamic field the same frictional effect as an actual polymer molecule. The size of a hydrodynamically equivalent sphere may be different for different types of motion of the macromolecule, e.g. for diffusion and for viscous flow.

Related Terms:
1) polymer molecule (http://doi.org/10.1351/goldbook.M03667).
2) diffusion (http://doi.org/10.1351/goldbook.D01716).

Source: Purple Book, 1st ed., p. 60 (http://old.iupac.org/publications/books/author/metanomski.html)

Citation: 'hydrodynamically equivalent sphere' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.H02896

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