ISSN:
1435-1536
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Description / Table of Contents:
Zusammenfassung Es wurde der Einfluß der Tensidkonzentrationc s auf die Gleichgewichtsdickeb r von Schaumfilmen und das Potential ϖ0 der diffusen elektrischen Doppelschicht in einem weiten Konzentrationsbereich (einschließlich cmc) für nichtionische Tenside (Decylmethylsulfoxide, Nonylphenol-20-Glycolether und Dodecyl-11-Ethylenoxid) und ionogene Tenside (Natriumlaurylsulfat) studiert. Nach dem Erreichen eines konstanten Wertes (= Plateau in derb r (c s )-Kurve) bei höheren Konzentrationen (etwa crnc) wird eine Abnahme in der Gleichgewichtsdicke der nichtionogenen Tenside gefunden. Dies hängt wahrscheinlich mit dem elektrostatischen “disjoining pressure” zusammen. Aus den Überlegungen über das ϖ0-Potential wird gefolgert, daß für nichtionogene Tenside die Oberflächen-ladungssättigung nahe bei der Sättigung in der Adsorptionsschicht liegt. Bei ionogenen Tensiden liegt die Sättigung in der Adsorptionsschicht bei höheren Konzentrationen.
Notes:
Summary The effect of the surfactant concentrationc s on the equilibrium thicknessh r , of foam films and the potentialϕ 0 of the diffuse electric layer is studied in a wide concentration range (including cmc). The cell for investigation of thin liquid films is improved and a good reproducibility of the measuredh r is obtained. The possibilities for determination of the capillary pressureP σ in.the cell for investigation of microscopic thin liquid films are discussed. The values ofP σ can be measured with sufficient accuracy by the capillary-rise method, using a tube, identical with the tube of the cell for thin liquid films. The dependenceh r (c s ) is studied for nonionic surfactants (decylmethyl sulphoxide, nonyl-phenol 20-glycol ether and dodecyl 11-ethylene oxide) and the ionic sodium dodecyl sulphate. After reaching a steady value (a plateau in theh r (c s ) curve) at high concentrations (about cmc) a decrease in the equilibrium thickness of nonionic surfactants is found. The possible reasons for this decrease are discussed. It is shown that this effect probably is due to the electrostatic disjoining pressure. The values of theϕ o-potential at the plateau of theh r (c s ) curves are determined by the DLVO-theory using theh r , values. The so determinedϕ 0-values are more correct than the obtained earlier by this method because of the more precise measurement of the equilibrium thickness and the direct experimental determining of the capillary pressure. A qualitative interpreting of theϕ 0(c s ) dependence is made on the basis of the surfactant adsorption at the solution/air interface and it is found that for nonionic surfactants the surface charge saturation is very near to the saturation in the adsorption layer, and for the ionic surfactants the adsorption layer saturation is at higher concentration.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01761121
Permalink
