A study of the polarographic characteristics of the Ti(IV)‐Ti(III) couple in methanolic solutions containing various concentrations of normalHCl and normalLiCl has been the basis for the determination of the oxidation state of titanium during dissolution in these media. The Ti(IV) and Ti(III) complexes have been shown to have the same number of chloride ligands. It is also shown that titanium dissolves with an apparent oxidation number (n app) between 3 and 4, with the value approaching 3 at high chloride concentrations. The acidity appears to have little effect at acidities greater than 0.10M. It is also shown that Ti(IV) in methanol solutions containing a high chloride ion concentration oxidizes Ti to form Ti(III). The nature of the complexes of titanium ion in solution and their effect on the titanium dissolution is discussed.

Polarographisch in methanolischen Lösungen, die HCl und LiCl in verschiedenen Konzentrationen enthalten, wird der Oxidationszustand von Ti während der Auflösung in diesen Medien bestimmt.

Publication costs assisted by the North American Rockwell Corp.The electrochemical behavior of the Ti(III) |Ti(IV) couple was investigated in methanol solutions containing 0.02-0.22 M chloride ion and 0.02-7.0 M water. The presence of two electrochemically distinct Ti(III) complexes was observed and the mechanism of the electrode processes was shown to consist of the reactions e-+ Ti(IV) ^Ti(IH)(a) (E1/2 ~-0.4 V); Ti(III)(a) + H20 ^Ti(III)(b) + C1"(K); Ti(III)(b)T i(IV) + e~( E1/2 ~0.1 V). The equilibrium constant K was evaluated from pulse polarographic and cyclic voltammetric data to be 0.029 ± 0.006. The reaction rates have been calculated from the kinetic contribution to the kinetic polarographic current, and the parameters ks and a of the first electron transfer reaction were estimated from pulse polarographic data. Combining these results with electron spin resonance measurements, the species Ti(III)(a) comprised [TiCl2(CH3OH)4]+ and [TiCl(CH3OH)5]2+. These two species equilibrate rapidly on an electrochemical time scale. Ti(III)(b) was assigned the structure [TiCl(CH3OH)4H20]2+. In addition, the Ti(IV) in methanol containing more than 0.3 M H20 contains at least one more water ligand than the Ti(III), based on the negative shift of the half-wave potential with the concentration of water.