Complex formation between Fe(III) and tartaric acid (H2L) has been studied in O.5M NaNO3 medium at 25° by potentiometry at pH 4.5-11. The following complex species and corresponding values of the stability constants (charges omitted) are proposed: 2Fe + 2L + 5H2O → Fe2(OH)5L2 + 5H+; log* β-522 = 4.95 Fe + L + 3H2O → Fe(OH)3L + 3H+; log* β-311 = -1.55 Fe + L + 5H2O → Fe(OH)5L + 5H+; log* β-511 = -21.2 These results are in good agreement with those reported for this system in acid. The results may be presented as the degeneration of the "core + link" mechanism observed in the acidic zone. Structures are suggested for the complex species formed. © 1992.