Surface Films

Abstract

READERS of Dr. Langmuir's stimulating and detailed review of my book, “The Physics and Chemistry of Surfaces” (NATURE, NOV. 8), may possibly suppose that there is an important difference of opinion on fundamental questions of the structure of surface films, from the criticism which he makes of one remark in the book. This I do not believe is the case; the differences, if there are any, relate to points of detail only. Dr. Langmuir appears to think I am disputing the fact that the heads of the molecules anchor them to the water and so cause spreading from bulk material on the surface; but this fundamental fact, which he himself established, is not doubted by any worker in this field, so far as I know, and has been confirmed without exception in many thousands of my own experiments. It is rather important that no impression of disagreement should be given on this matter; the water-soluble or ‘polar’ group unquestionably anchors the molecules to the surface, and if the attraction of this group is weakened sufficiently, the film either becomes unstable or cannot be formed at all. This anchoring is equally important in all classes of films, condensed, expanded, and gaseous.