Untersuchungen über das Desorptionsverhalten einiger löslichern-Alkansäuren an der Wasser-Luft-Grenzfläche

Adsorption layers of aqueous hydrochloric solutions of normal pentanoic, hexanoic, heptanoic, octanoic and decanoic acid were compressed after having reached adsorption equilibrium. In most cases after a certain time the compressed surface layer reached a constant surface tension value which lies below the value for the adsorption equilibrium. The difference between both values can amount to some dynes/cm and depends on the kind and concentration of the surfactant and the compression ratio. The time intervals necessary for establishing desorption equlibrium for various systems have been calculated using several theoretical models. Special experiments and theoretical considerations give evidence for the presence of small amounts of strongly surface active impurities causing the surface tension discrepancies. The problem of characterizing the specific effect of a surfactant is discussed in connection with purity.