Dy. Kwok et al., AXISYMMETRICAL DROP SHAPE-ANALYSIS AS A FILM BALANCE, Colloids and surfaces. A, Physicochemical and engineering aspects, 88(1), 1994, pp. 51-58
A pendent drop experiment is used to demonstrate the possibility of us
ing a surface tension measurement technique, axisymmetric drop shape a
nalysis-profile (ADSA-P), as a film balance. Owing to the fact that bo
th the values of the surface tension and the surface area are outputs
of ADSA-P, a continuous measurement of the surface tension as a functi
on of the surface area is possible using a motor-driven syringe to cha
nge the drop volume. In the case of an insoluble monolayer on the drop
surface, the surface tension as a function of the surface area consti
tutes de facto film balance measurements. As an illustration, such ''f
ilm-balance'' measurements on a monolayer of octadecanol are presented
and compared with conventional him balance measurements. It is shown
that the results found by ADSA-P are in good agreement with those from
the conventional film balance measurements. As a film balance, ADSA-P
offers a range of possibilities which are discussed briefly.