title: Effect of surfactant adsorption time on the observation of Newton black film in foam film.
abstract: Observation of Newton black film (NBF) in foam film is possible only with a certain probability W which depends on the concentration C of surfactant in the solution and on the time t(a) during which adsorption of surfactant at the solution/air interface has taken place. In the paper, the W(C,t(a)) dependence is derived and used to analyze the effect of t(a) on the critical surfactant concentration C(c) below which NBF in foam film practically cannot be observed. An expression for the C(c)(t(a)) function is obtained which reveals that C(c) decreases substantially with increasing t(a). This expression is found to describe well experimental C(c)(t(a)) data for foam films obtained from aqueous solution of the therapeutic surfactant INFASURF.
authors.affiliation: Institute of Physical Chemistry, Bulgarian Academy of Sciences, ul. Acad. G. Bonchev 11, Sofia 1113, Bulgaria.
authors.forename: Dimo
authors.initials: D
authors.lastname: Kashchiev
authors.forename: Dotchi
authors.initials: D
authors.lastname: Exerowa