Is the Frumkin (Fowler–Guggenheim) adsorption isotherm a two- or three-parameter equation?

The Frumkin or Fowler–Guggenheim isotherm, which has three fitting parameters, is often converted to a linear form with two parameters facilitate parameter estimation by regression. This conversion made possible way of replacing the unknown capacity isotherm surrogate value. certain simple isotherms (e.g., Dubinin–Radushkevich) are used as surrogates. However, such surrogates have never been evaluated for validity accuracy. In this paper, three-parameter was fit previously published data identify all including parameter. cases examined, fitted values were found differ rather significantly from in two-parameter isotherm. dubious practice transforming into should be discarded favor estimating nonlinear