Of component $$i$$, defined by the equation $\mathit{\Gamma}_{i}^{(n)} = \mathit{\Gamma}_{i}^{\unicode[Times]{x3C3} }- \mathit{\Gamma}_{i}\ \frac{c_{i}^{\unicode[Times]{x3B1} } - c_{i}^{\unicode[Times]{x3B2} }}{c^{\unicode[Times]{x3B1} }- c^{\unicode[Times]{x3B2} }}$ where $$\mathit{\Gamma }^{\unicode[Times]{x3C3} }$$, $$c^{\unicode[Times]{x3B1} }$$ and $$c^{\unicode[Times]{x3B2}}$$ are, respectively, the total @[email protected] concentration and the total concentrations in the bulk phases α and β: $\mathit{\Gamma}^{\unicode[Times]{x3C3} }=\sum _{\begin{array}{c} i \end{array}}\mathit{\Gamma }_{i}^{\unicode[Times]{x3C3} }$ $c^{\unicode[Times]{x3B1} }=\sum _{\begin{array}{c} i \end{array}}c_{i}^{\unicode[Times]{x3B1} }$ $c^{\unicode[Times]{x3B2} }=\sum _{\begin{array}{c} i \end{array}}c_{i}^{\unicode[Times]{x3B2}}$ The reduced adsorption is invariant to the location of the @[email protected] Alternatively, the reduced adsorption may be regarded as the @[email protected] concentration of $$i$$ when the @[email protected] is chosen so that $$\mathit{\Gamma }^{\unicode[Times]{x3C3} }$$ is zero, i.e. the @[email protected] is chosen so that the reference system has not only the same volume, but also contains the same total @[email protected]($$n$$) as the real system.