Vol. 59
480
COMMUNICATION TO THE EDITOR MONOLAYER STRUCTURE AS REVEALED BY ELECTRON MICROSCOPY Sir :
the process of transferring the monolayer from the water to collodion support, which could be simply tested by comparing the area of the f ilm on the collodion support with the decrease in area of the film, The electron micrographs of Ries and Kimballl a t constant surface pressure, on the Langmuirof films of n-hexatriacontanoic acid a t various stages Adam trough, or (2) assuming that there has been of compression are very interesting and recall the no change in film area during transfer, the islands ultra microscopical investigations of Zocher and may not, in fact, be monomolecular and that some collapse has already begun. This explanation reStiebel. Their explanation, however, presents certain ceives some support from the authors’ observation difficulties which must be explained if the observa- that the surface pressures are unstable in this tions are not to be attributed to artefacts intro- region. On this assumption, Fig. 1C presents no duced by this novel technique. For example, Fig. difficulty since the multimolecular islands might be 1B apparently shows islands of film, which the expected to grow and cohere on further compresauthors calculate to be one molecule thick, cover- sion until the whole system ultimately crumples ing only about half the surface and surrounded into quasi fibers as in Fig. 1D. either by a clean surface or a very attenuated monoElectron micrographs of fdms a t areas larger than layer, the whole system exerting a surface pressure 20.4 per molecule might be very informative of 15 dynes/cm. While the force-area curves are since here patches of coherent monolayer in a cirnot given, it is obvious that a t this pressure the film cumambient gaseous monolayer are known to exist area must be less than 20.4 A.z per molecule, i.e., and can be demonstrated by fluctuations in surface the extrapolated area corresponding to a close pack- potential from point to point. ing of the hgdrocarbon chains. There seem to be LEATHER MANUFACTURERS’ two possible explanations of this anomaly: Either BRITISH RES~ARCH ASSOCIATION (1) the island structure has been introduced during MILTON PARK,EGHAM KENNETH G. A. PANKHURST SURREY,ENGLAND (1) Ries and Kimbsll, J . Phys. Chem., 69, 94 (1955). (2) Zocher and Stiebel, 2.physik Chem., 147A 401 (1930).
RECEIVED FEBRUARY 7,1955
b
3
