The formation of uranyl complexes of N‐acetyl, ‐chloroacetyl, ‐benzoyl and ‐o, ‐m and ‐p nitrobenzoyl N‐phenylhydroxylamines have been studied potentiometrically in 1:1 aqueous acetone at constant ionic strenght (m̈ = 0.5). Only the first step could be followed and the final results have been evaluated by projection strip method. The stabilities follow a general order. Copyright © 1970 Verlag GmbH & Co. KGaA, Weinheim