polymer formation and aldol condensation by a hydrocarbyl aldehyde is prevented by adding to the aldehyde a trace to minor amount of readily oxidizable metals or cations having oxidation potentials greater than about - 0 . 2 volts . in a typical embodiment , a liquid containing a hydrocarbyl aldehyde is inhibited against aldol condensation by incorporating in the liquid from about 0 . 005 to about 1 . 0 weight percent thereof of the aforementioned metals or cations .