Chemical reactivity and electrical conductivity of hydrous ferric oxide

Abstract

Ferric oxide was prepared by precipitation in a mixture of ammonium hydroxide and ferric nitrate at 90°C followed by ageing in water at 25°C, and annealing at 110°C. Thermal, X-ray and thermogravimetric analysis all suggest the existence of a kind of “bound water” that vaporizes at about 170°C and “crystallization water” that vaporizes at about 300°C. Ir and nmr spectra suggest that the bound as OH.The effect of the bound water on chemical reactivity of the ferric oxides was examined with the catalytic decomposition of hydrazine sulphat alkaline solution: the activity for the catalytic decomposition increased with ingcreasing amount of bound water in the oxide. The bound water also affects the electrical conductivity of the oxide. In the empirical equation, i = i0 exp (-E/2kT, for the current of the oxide under constant voltage, the apparent activation energy E and the temperature-indepedent current i0 both decrease with increasing amount of bound water. Furthermore, the current i increases exponentially with increase of the amount of the bound water. It is concluded that the bound water in the oxide provides the active sites for both surface chemical reaction on and chemical conduction in ferric oxide.