Dynamic measurements of dilational properties of a liquid interface

✍ Scribed by J. Lucassen; M. Van Den Tempel

• Publisher: Elsevier Science
• Year: 1972
• Tongue: English
• Weight: 719 KB
• Volume: 27
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(72)80104-0

✦ Synopsis

A new method is described for the measurement of dilational surface properties of solutions containing surface-active materials. The surface dilational modulus is obtained from a surface-tension variation, caused by a small-amplitude, sinusoidal-area variation. The method is limited to frequencies below about 0.1 Hertz because at higher frequencies wave-propagation effects play a disturbing role.

Simultaneous measurement of the phase difference between area changes and surface-tension variations provides information about possible relaxation processes occurring on the surface.

The use of the method is illustrated by means of experiments on dilute solutions of decanoic acid. For this system, the relaxation process consists of diffusional exchange of solute between bulk and surface. A quantitative analysis of this phenomenon shows satisfactory agreement with the measured behaviour of the modulus as a function of frequency and concentration.