The general molar flux, $N_A,$ in a stationary frame of reference in a binary system of components A and $B$ is the sum of the molar diffusional flux of component A and the flux of component A due to the bulk flow of the mixture as given in Equation $1.$

$N_A=J_A+\frac{C_A}{C_T}(N_A+N_B)$

$($Equation $1)$

Integrate the general molar flux equation with the limits of the integrals: at $Z=Z_1,C_A=C_{A1}$ and at $Z=Z_2,C_A=C_{A2}$ and show that

$N_A=(\frac{N_A}{(N_A+N_B)})(\frac{D_{AB}{P}_T}{RTZ})ln(\frac{\frac{N_A}{(N_A+N_B)}-y_{A2}}{\frac{N_A}{(N_A+N_B)}-y_{A1}})$