ANALYSIS OF HYDROLYSIS PRODUCTS OF IRON(III) SALT-SOLUTIONS BY MEANS OF MOSSBAUER SPECTROMETRY AND X-RAY DIFFRACTOMETRY

Hydrolysis products of iron(III) salt solutions of pH 1.5~1.8 were analyzed. It was found that α-FeOOH precipitates in the presence of nitrate or bromide ions whereas β-FeOOH precipitates if the solution contains fluoride or chloride ions. NaFe3(SO4)2(OH)6 is obtained in the crystal form when the solution includes sulfate ions. Chemical state and crystal structure of the precipitates depend on the stability of Fe(III) complexes in the solution and on the concentration of anions. The contents of chlorine and bromine in the hydrolysis products were determined by means of thermal-neutron activation analysis. The γ-ray spectra were measured by a 1024 channel pulse height analyzer and a Ge(Li) detector. Atomic ratios, F/ Fe and Cl/Fe in β-FeOOH, Br/Fe in α-FeOOH, were found to be 0.55, 0.15 and 0.012, respectively. The desorption behaviours of chlorine from β-FeOOH and of bromine from α-FeOOH indicated that chlorine is included tightly whithin β-FeOOH crystal whereas bromine is adsorbed loosely on the surface of α-FeOOH crystal. The processes of iron III) hydrolysis reactions in the various anions were also discussed from the standpoint of solution chemistry. Mossbauer spectra of β-FeOOH with fluolide ions and of β-FeOOH with chloride ions were taken at 78 K. The results indicated the slight difference in the internal magnetic field; 46.3 ±0.3T for the former and 47.2±0.3T for the latter. © 1979, The Chemical Society of Japan. All rights reserved.