Аннотация:It is shown by recording of electrocapillary curves that formaldehyde when added to neutral, butyl-alcohol-containing solutions produces a small additional depression of the interfacial tension of mercury, while in acidic solutions of butyl alcohol the interfacial tension is independent of the presence of formaldehyde. At the solution/air interface at pH 7 one sees a small decrease in the surface activity of butanol when formaldehyde is present, which appears to be due to solvation of the alcohol molecules by formaldehyde molecules. Because of strong hydration of the formaldehyde molecules, in acidic solution the surface activity of butanol is independent of the presence of formaldehyde.