Term: intrinsic viscosity https://doi.org/10.1351/goldbook.I03140 Definition: The limiting value of the reduced viscosity, ηi/c or the inherent viscosity, ηinh, at infinite dilution of the polymer, i.e. \[[\eta] = \lim _{c\rightarrow 0}\frac{\eta _{\text{i}}}{c}=\lim _{c\rightarrow 0}\eta _{\text{inh}}\] Notes: 0) This term is also known in the literature as the Staudinger index. 1) The unit must be specified; cm3 g-1 is recommended. 2) This quantity is neither a @V06627@ nor a pure number. The term is to be looked on as a traditional name. Any replacement by consistent terminology would produce unnecessary confusion in the polymer literature. Synonymous with limiting viscosity number. Related Terms: 1) viscosity (http://doi.org/10.1351/goldbook.V06627). 2) reduced viscosity (of a polymer) (http://doi.org/10.1351/goldbook.R05220). 3) inherent viscosity (of a polymer) (of a polymer) (http://doi.org/10.1351/goldbook.I03033). Source: Purple Book, 1st ed., p. 63 (http://old.iupac.org/publications/books/author/metanomski.html) Citation: 'intrinsic viscosity' 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.I03140 License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.