## phenomenological equation

https://doi.org/10.1351/goldbook.P04540
In the following only media which are @I03353@ with respect to mass transport (i.e. the transport coefficients are independent of direction) are being considered. In the @L03558@ (not too far from equilibrium), for uniform temperature and neglecting external fields such as the earth's gravitational field, the flux density of species B is related to the gradients of the electrochemical potentials of all species by the phenomenological equation: $N_{\text{B}}- c_{\text{B}}\ v_{\text{A}}=- \sum _{\begin{array}{c} i\\ i\neq A \end{array}}L_{\text{B}i}^{\text{A}}\ \nabla \mu _{i}$ with $i=\text{B},\text{C},...$ where $$\nabla \mu _{i}$$ is the @G02669@ of the @E01945@ of species i. The proportionality factors $$L_{\text{B}i}^{\text{A}}$$ are called phenomenological coefficients. Their values depend on the frame of reference. The latter is taken here to move with the velocity $$v_{\text{A}}$$ of species A, and hence: $L_{\text{A}i}^{\text{A}}=0$
Source:
PAC, 1981, 53, 1827. (Nomenclature for transport phenomena in electrolytic systems) on page 1830 [Terms] [Paper]