00969 IUPAC Gold Book - change ratio of a quantity 10.1351/goldbook.C00969 C00969 current 1 A term which may be expressed infinitesimally at time \(t\) by a ratio of differentials \(\frac{\rm{d}Q_{1}(t)}{\rm{d}Q_{2}(t)}\) where the kind of quantities are the same but for different components in the same system. In practice, the ratio for a finite interval is: \[\frac{\Delta Q_{1}(t_{1};\,t_{2})}{\Delta Q_{2}(t_{1};t_{2})}\] Examples are: mass change ratio, \(\frac{\rm{d}m_{1}(t)}{\rm{d}m_{2}(t)}\); amount of substance change ratio, \(\frac{\rm{d}n_{1}(t)}{\rm{d}n_{2}(t)}\). amount of substance https://goldbook.iupac.org//terms/view/A00297 PAC, 1992, 64, 1569. 'Quantities and units for metabolic processes as a function of time (IUPAC Recommendations 1992)' on page 1571 (https://doi.org/10.1351/pac199264101569) https://goldbook.iupac.org/terms/view/C00969/html https://goldbook.iupac.org/terms/view/C00969/json https://goldbook.iupac.org/terms/view/C00969/plain Citation: 'change ratio of a quantity' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.C00969 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. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . 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. 2026-04-19T00:35:10+00:00