The @S06171@ amount or Gibbs adsorption of component \(i\), \(n_{i}^{\sigma }\), which may be positive or negative, is defined as the excess of the amount of this component actually present in the system over that present in a reference system of the same volume as the real system and in which the bulk concentrations in the two phases remain uniform up to the @G02635-1@. That is \[n_{i}^{\sigma }=n_{i}- V^{\alpha }\ c_{i}^{\alpha }- V^{\beta }\ c_{i}^{\beta }\] where \(n_{i}\) is the total amount of the component \(i\) in the system, \(c_{i}^{\alpha }\) and \(c_{i}^{\beta }\) are the concentrations in the two bulk phases \(\alpha \) and \(\beta \), and \(V^{\alpha }\) and \(V^{\beta }\) are the volumes of the two phases defined by the @G02635-2@.