Chromium speciation implies the quantitative determination of Cr(III) and Cr(VI). However, the presence of hydrolytic forms of Cr(III) and the instability of tracer level Cr(VI) in acid media complicates this speciation. The present work describes the stability of several monomeric Cr(III) species formed in the acid reduction of51Cr(VI). The distribution of Cr(VI) and Cr(X)n(H2O)
as a function of time was followed by paired cationic and anionic exchange analyses. The distributions and their time dependences are functions of the initial concentrations of both Cr(VI) and acid. The Cr(III) species eventually level to the hexaaquo form.