The speciation of tetravalent technetium has been studied in HCl solutions
ranging from 1.0 to 6.0 M. Tc(IV) exists in 6.0 M HCl as the well character
ized TcCl62- chloride complex. In 1.0 M HCl, the chloride ligands of TcCl62
- are slowly substituted by other ligands such as H2O. OH- or O2-. SO TcClm
On(OH)(p)(H2O)(q)((4-m-2n-p)+) compounds may form with (m+n+p+q) = 6. Sever
al speciation techniques such as W-visible and Raman spectrometries, X-ray
absorption spectroscopy and electrochemistry have enabled to get an insight
into this problem. All the results have indicated two most likely species
of Tc(TV) after aging for about ten days in 1.0 M HCl to be aquo-chlorocomp
lexes of technetium and not oxo-chorocomplexes: TcCl5.H2O- and TcCI4. 2H(2)
O.