IONIC-STRENGTH DEPENDENCE OF FORMATION-CONSTANTS .18. THE HYDROLYSIS OF IRON(III) IN AQUEOUS KNO3 SOLUTIONS

The hydrolysis of iron(III) was studied potentiometrically at differen t ionic strengths in KNO3 aqueous solutions, at 25-degrees-C, to deter mine the dependence of hydrolysis constants on ionic strength (nitrate media), to check the existence of nitrate-ferric ion interactions, an d to confirm the formation of high polymeric species. Under the experi mental conditions 0.03 less-than-or-equal-to I (KNO3) less-than-or-equ al-to 1M, 0.3 less-than-or-equal-to C less-than-or-equal-to 12 mM, the species Fe(OH)2+, Fe2(OH)24+, Fe(OH)2+ and Fe12(OH)342+ were found, a nd the hydrolysis constants log beta11 = 2.20, log beta12 = -2.91, log beta22 = -5.7, log beta12.34 = -48.9 (I = 0M) were calculated. The io nic strength dependence of hydrolysis constants is quite close to that found for several protonation and metal complex formation constants r eported elsewhere.