Considerations of the errors in the electrosorption energy values associated with method of determination of these values from the plots of In [(l -e)x,/@j vs 0 have been presented. The possible sources of the errors have been indicated. From the theoretical Flory-Huggins/Parsons example and experimental electrosorption isotherms, the main contributions to the error of the extrapolated Gibbs electrosorption energy value have been evaluated. T'he results have been tabulated and illustrated. They show that the curvatures observed on the experimental plots of In [ (l-&x,/e] its 0 should not be ignored and may necessitate reconsideration of the interpretation and main assumptions. The value of the stoichiometric coefficient in the adsorption4esorption process, n, has a non-negligible effect on the electrosorption energy values. The influence of the n value on the magnitude of errors has been examined. Other possible errors related to the departure from Frumkin's description of the molecular interactions at the interface have been examined as well. The experimental electrosorption isotherm of I-propanol at an aqueous mercury-sodium sulfate interface, at different electrode potentials, as well as theoretical equations, comprised the basis of these investigations.