ECEST interest in the use of ferrate compounds as strong ' oxidizing agents prompted an investigation of some factors influencing the stability of potassium ferrate solutions. In a study of the st,ahility of ferrate ions in aqueous solutions, Schreyer and Ockerman (2j found that the more dilute solutions of ferrate are more stable. They found also that some added salts, after increasing the initial deconiposition rate of ferrate solutions, apparently staliiljze the remainder; and that ferrate ions are more stable in buffer solutions of p H 8 than those of pH 7. These authors believe that the major factor influencing stability is the alkalinity of the solution. From qualitative experiments Schreyer ( 1 ) reported that solutions of potassium ferrate were partially decomposed photochemically over a period of 9.5 hours.Since it seemed desirable to establish the factors influencing the stability of ferrate compounds in connection with other xork, a quantitative study of t,he effects of light, temperature, alkalinity, and concentration, on the decomposition of aqueous solutions of potassium ferrate was made under carefully controlled conditions. PROCEDUREThe potassium ferrate was prepared by the method reported by Thompson, Ockerman, and Schreyer (4). To determine the effect of light on the decomposition rate of solutions of potassium ferrate under varying conditions, each of the experiments described below was performed using identical solutions in three flasks placed in a thermostat. One flask was exposed to the daylight in the laboratory, one was placed in the path of a beam of light from a 150-m-att G.E. spotlight, and one was painted black to exclude light. The latter was fitted with a rubber stopper containing a release valve to permit the escape of oxygen.As it was impossible to maintain a constant temperature with the splotlight shining directly on the bath, a 3000-ml. beaker of water was inserted between the bath and the spotlight to absorb most of the heat radiation. In this manner the temperature was successfully maintained constant to within +O.l O C.The solutions were analyzed by pipetting 10-ml. portions and determining the ferrate concentration by the chromite method ( 3 ) . Analyses were performed at varying intervals over a 2-hour period after the potassium ferrate solutions were prepared.Preliminary experiments indicated that several factors such as stirring, vibrations, and exposure of dry samples to the atmosphere influenced the decomposition. To minimize these factors the solutions were not stirred, and every effort was made to maintain constant conditions except for the one condition varied in 1 Present address, University of Cincinnati, Cincinnati, Ohio. rvlc each series of experiments. obtained.In this way reproducible rcwults were RESULTSEffect of Temperature. To study the effect of temperature on stability, quantitative determinations 15-ere made on aqueous solutions of potassium ferrate at' temperatures of 25' and 0.5' C. The results in Figure 1 shox that at 25" C. the concentration of potass...
Methods are described for the preparation and analysis of barium ferrate(VI). Barium chloride dihydrate is added to potassium ferrate and barium ferrate is obtained as a maroon precipitate, 86.5% pure. The chromite method for analysis of soluble ferrates has been modified for application to insoluble barium ferrate. RECENT interest in the use of the ferrate ion as a strong .
\ NALYTICAL separations and determinations of elements in Groups III and IV of the periodic chart are often very difficult because of the formation of precipitates of poor quality. For example, the separation of zirconium from other positive ions by the precipitation of zirconium phosphate is often not nearly as effective as might be predicted on the basis of solubility differences.
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