The Unimolecular Film in Heterogeneous Reactions

Abstract

THE formation of unimolecular films on solid surfaces has been demonstrated by Langmuir¹ for gases and by Carver² for toluene, but others employing different materials have obtained results interpreted as indicating an adsorbed layer of multi-molecular character. At the moment the position is such that “definite agreement about the validity of direct experimental evidence is hardly reached”³ and for this reason it may be of value to record the discovery of two unimolecular films made during our most recent work on the combination of hydrogen with sulphur in Pyrex glass. For the first time, so far as we are aware, this reaction has now been studied at low hydrogen pressures of the order of 3 mm. at the temperature employed, namely, 343° C. In the light of previous experience⁵, the most rigid precautions were taken to ensure the absence of oxygen or moisture from the reactants.