Formation of films in hydrolysing ferric chloride solutions

Abstract

FRYER et al.^1,2 have postulated that two-dimensional polymeric structures may be formed in solution when metal-ion salts undergo self-hydrolysis before the precipitation of some hydrated crystalline oxides such as α FeO.OH, beta; FeO.OH, and V₂O₅.H₂O. They reported that these structures or films can only be seen by spraying a hydrolysing solution onto a mesh of asbestos fibres when the film appears suspended between the asbestos fibres supported on the copper grid. We describe here how we have repeated this work using 0.01 M FeCl₃ with both an asbestos mesh and a holey carbon support film (Fig. 1) and have obtained similar results. The films we have seen have large dimensions, of the order of several microns and of varying thickness depending on the drop size of the spray and the size of the mesh or hole. Assuming that the minimum thickness of the film is about the same as that of the partially hydrolysed spherical polymers seen by Murphy et al.³, that is, 10–50 Å then the equivalent spherical diameter (e.s.d.) of the films would be about 3,000 Å. Our observations of the films suggest that they can be much thicker than this.