Abstract: The invention relates to a process for the determination of iodine in low concentration in a nitrate solution, particularly a uranyl nitrate solution.According to this process, to the sample to be determined is added a reducing agent such as ascorbic acid in order to maintain the iodine in the iodide state, followed by the measurement of the potential difference E.sub.1 between a selective iodide ion electrode (5) and a reference electrode (7), after which there is a successive addition of a first and a second iodide solution having known iodide concentrations and containing a reducing agent, accompanied by the measurement after each addition of the potential differences E.sub.2 and then E.sub.3 between the electrodes (5) and (7), followed by the calculation from E.sub.1, E.sub.2 and E.sub.3, the concentrations and volumes of the additions, the initial iodine concentration of the solution.