The properties of fluid films depend on the nature of the film
phase and that of each of the two neighbouring bulk phases. These films should be
described, where appropriate, by three capital letters such as A for air, W for water,
O for oil, and S for solid, separated by solidi, the middle letter indicating the
phase. For symmetrical films the first and last symbols are the same, e.g. A/W/A:
in air, or W/O/W: oil film
in water, whereas for unsymmetrical films these are different, e.g. W/O/A: oil film
between water and air.
PAC, 1972, 31, 577
(Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix
II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry)
on page 613
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook