instantaneous rate of flow

in polarography
https://doi.org/10.1351/goldbook.I03063
The rate of increase of the mass of a drop at a particular instant \(t\) seconds after it has begun to form.
Source:
PAC, 1985, 57, 1491. (Recommended terms, symbols, and definitions for electroanalytical chemistry (Recommendations 1985)) on page 1504 [Terms] [Paper]