Fluorescence drainage profiles of thin liquid films.
Fluorescence drainage-profiles of thin liquid films formed from Rhodamine solutions containing anionic, cationic and non-ionic surfactants have been investigated. It is found that the influence of system variables such as electrolyte concentration, dye concentration, film environment and solution viscosity can be evaluated by means of the profiles. The addition of sodium chloride leads to the expansion (non-ionic surfactant), or contraction (anionic surfactant) of the profiles. In the case of the cationic surfactant, it reduces the number of fringes in the profiles. The height of selected fringes changes linearly with dye concentration, and no fringes are observed when the films are submerged in non-polar solvents. The influence of solution viscosity on film thickness and drainage rate is demonstrated by the number and frequency of fringes in the profile. The formation of first and second "black films" from solutions containing varying concentrations of sodium chloride can be shown.
Fourier transform infrared study on black soap films
Fourier transform infrared (FT-IR) spectra in the range 3800–2800 cm−1 have been recorded of the first and second black films in air prepared from aqueous solutions of sodium dodecylsulfate (SDS) without and with the addition of sodium chloride, respectively. It is found that in both films the methylene chains of SDS, which are located outside the aqueous core of the sandwich structure, are in an oriented liquid crystalline state. In a first black film, the thickness of the aqueous core is determined to be 9.6 nm, by recording polarized infrared spectra with various angles of incidence to the film surface, and by analyzing them with the aid of thin layer optics. It is found that this value varies in the range 5 ~ 10 nm from film to film. The extinction coefficients of the aqueous core are also examined. In the second black film, the thickness of the aqueous core is found to be about 1 nm. The OH stretching band of water in the second black film appears at appreciably higher wavenumbers (by 60 cm−1) than t...
Potentiometric dissociation constants and analytical properties of α-mercaptobenzeneacetic acid
Abstract The α-mercaptobenzeneacetic acid has been synthesized and screened for its properties as an analytical reagent. The acid dissociation constants have been determined potentiometrically in 0.1 M KNO 3 and 0.5 M KNO 3 ethanol-water 20% (v/v) solutions at 25 ± 0.1 °C.