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TiOY2-solutions may then be stored for a long time (over a month) without any special care.Current efficiency for electrolytic generation of Ti(II1) may be evaluated by the Lingane Method ( 1 1 ) from the current density potential graphs plotted in Figures 2 and 3 for platinum and mercury electrodes, respectively. A very good current efficiency (>0.996) is obtained with the mercury electrode throughout the current density region available with our apparatus (Figure 4, curve a ) but with the platinum it is never as good (Figure 4, curve b ) and falls down sharply when the current density is high, because of competition of hydrogen ion reduction.Titration Efficiency. The homogenous reoxidation of electrogenerated Ti(II1) to Ti(1V) by a variety of organic or inorganic oxidants is very fast and quantitative. It is therefore possible to carry out a series of coulometric titrations with the same Ti(1V) electrolytic solution in the same vessel.For example, we report here experimental results on the titration of samples of aromatic nitroso compounds (Table 11) performed successively in the same electrolytic solution.Titration efficiency is better than 99% for all the compounds but the last. The lack of purity of the products available probably accounts for these results.Application of these results to selective coulometric titrations of organic compounds are presented elsewhere (22, 23). LITERATURE CITED(1) J.