SPECTROPHOTOMETRIC IN SITU STUDY OF THE COMPOSITION OF SATURATED AND UNSATURATED VAPORS OF IRON (III) CHLORIDE IN THE TEMPERATURE RANGE 150—800 °C

Abstract

We report initial results from our spectrophotometric study of the equilibrium «solid —
vapor» for iron chloride (III) in a wide range of temperatures (150—800 °C). The purpose of the
work was to determine (at least qualitatively) the composition of unsaturated vapor of iron chloride
(III). The experiment consisted in scanning absorption spectra of the vapor (wavelength interval
200—800 nm) in two temperature regimes: incremental increasing and decreasing. Obtained dependences
of the coefficient of absorption k on wavelength l at different temperatures showed that the
character of equilibrium changes at the temperature 231 °C: the saturated vapor turns to unsaturated.
The determination of this temperature let us measure concentration and pressure of Fe2Cl6. Further
studies of unsaturated vapor pointed that at high temperatures it experiences significant changes and,
probably, a new form FeCl2 appears. As metal halides are often used as transport agents for growing
sulfides, current results together with some future investigations in this field may find their application,
for example, as a base for pyrite production for the needs of technology and energetics.