Isolation of sodium 5‐allyl‐5‐(1‐methylbutyl) barbiturate from anhydrous butanol or aqueous ethanol gave rise to two products which differed in some physical properties. The material from the butanol procedure appeared to contain 30.7 per cent impurities whereas that from aqueous ethanol contained 9 per cent when both were subjected to the minimum solubility purity test. When the butanol material was reworked via the ethanol method, a purity test of the sample revealed the presence of only 3.1 per cent impurities. A consideration of the differences in the two procedures indicated that the presence or absence of water during the recovery of the solid secobarbital sodium influenced the amido‐imidol equilibrium in the recovered solid. This hypothesis was confirmed by infrared absorption spectra of mulls of the solid materials. The anhydrous butanol material gave a product whose amidoimidol equilibrium was displaced more towards the imidol form than the aqueous ethanol material. The displacement of tautomeric equilibrium of properly substituted sodium barbiturates isolated from anhydrous alkanol media may be general.