NOVELTY - Determining (m1) acid value of ethanol based on coulometric titration using equipments, comprising a current source, potential measurer and an electrochemical cell containing inert working electrode, platinum auxiliary electrode of silver, and a combined pH electrode containing an internal reference electrode, is claimed. The compartment (A) of the electrochemical cell contains sample mixed with inert supporting electrolyte working electrode, combined pH electrode and a magnetic stirrer, where the compartment (B) contains lithium chloride and silver auxiliary electrode.    USE - The methods are useful for determining acid value of ethanol and biodiesel.    ADVANTAGE - The method exhibits good accuracy, and obtains titration curves having good resolution and signal/noise ratio, thus allowing detecting more than one equivalence point on one curve and a good differentiation between consecutive equivalence points.    DETAILED DESCRIPTION - Determining (m1) acid value of ethanol based on coulometric titration using equipments, comprising a current source, potential measurer and an electrochemical cell containing three electrodes, that are inert working electrode, platinum auxiliary electrode of silver, and a combined pH electrode containing an internal reference electrode, is claimed. The compartment (A) of the electrochemical cell contains the sample mixed with an inert supporting electrolyte working electrode, combined pH electrode and a magnetic stirrer, where the compartment (B) contains 1-3 mol l--1 solution of lithium chloride, and a silver auxiliary electrode, and the titration is performed by switching between application cycles a constant electric current between the inert working electrode and silver auxiliary electrode for a defined time interval, with determining the amount of charges generated in cycles, and measuring potential of combination pH electrode. An INDEPENDENT CLAIM is also included for determining (m2) the acid value of biodiesel based on coulometric titration using the equipment comprising a current source, potential measurer and an electrochemical cell containing three electrodes, that are inert working electrode, platinum auxiliary electrode of silver, and a combined pH electrode containing an internal reference electrode.