The original Antoine equation has a 3 parameters or coefficients i.e. A, B and C. This provides good fit for all liquids given freedom to choose values for thse 3 parametrs to get the best fit.The equation fit sometimes become inadequate over wide range of the pressures (e.g. from 0.01 bar to 1000 bar) and in this case the fit can be imroved by the Extended Antoine Equation which has 5 parameters