For liquid-film control, there is no gas-phase resistance to mass transfer of A. Thus, in equation 9.2-14, 1/k_{A\ell } \gg 1/H_{A}k_{Ag}  and  K_{A\ell} = k_{A\ell} so that equation 9.2-22b may be written

\frac{1}{K_{Ag}}=\frac{1}{H_A k_{Ag}}+{1}{k_{A\ell}}       (9.2-14)

(-r_A)=K_{A\ell}(\frac{P_A}{H_A}+\frac{D_{B\ell}}{D_{A\ell}b}c_{B})       (9.2-22b)

(-r_{A})=(1+\frac{D_{B\ell } H_{A}}{D_{A\ell }b}\frac{c_{B}}{p_{A}} )\frac{k_{A\ell }}{H_{A}} p_{A}                      (9.2-25)