Ag. Bailie et al., SOLUBILITY OF POTASSIUM FERRATE IN 12 M ALKALINE-SOLUTIONS BETWEEN 20-DEGREES-C AND 60-DEGREES-C, Journal of chemical technology and biotechnology, 66(1), 1996, pp. 35-40
The solubility of potassium ferrate (K2FeO4) was measured in aqueous s
olutions of NaOH and KOH of total concentration 12 M containing variou
s molar ratios of KOH:NaOH in the range 12:0 to 3:9. Several analytica
l methods were tested for the determination of ferrate concentration.
The final method chosen consisted of potentiometric titration of the f
errate sample with an alkaline solution of As2O3. The assumption was m
ade that ferrate dissociates in concentrated KOH solutions predominant
ly to KFeO4-. The solubility constant, S, defined as the product of th
e molar concentration of the potassium ion, K+, and the ferrate anion,
KFeO4- was found to be 0.044 +/- 0.006 mol(2) dm(-6) for 20 degrees C
, 0.093 +/- 0.004 mol(2) dm(-6) for 40 degrees C and 0.15 +/- 0.09 mol
(2) dm(-6) for 60 degrees C. From these results the heat of dissolutio
n of K2FeO4 was calculated as -14.3 kJ mol(-1). At 60 degrees C the en
hanced decomposition of the ferrate at the higher temperature led to a
greater deviation in solubility values compared with data for either
20 degrees C or 40 degrees C.