The oxidation-reduction equilibrium of vanadium has been investigated by the dynamical method of Wartenberg and Aoyama. By the experiment it has been suggested that the chemical changes take place in the two stages under the experimental conditions, and the reactions might be expressed by the following: V+H2O\
ightleftarrowsVO+H2 and 2VO+H2O\
ightleftarrowsV2O3+H2. Thermodynamic calculations have been made for the above reactions, and the result of the calculated heats of formation agreed fairly well with that of the determina-tions made by other investigators.
In the above investigation, the polarized platinum electrodes by means of grid current, which is obtained by impressing a positive potential on the grid, were used in the potentiometric titrations. In this apparatus, the approach of the end point is indicated, thus the neither plotting or recording nor adjustments is necessary during the titration; but it is necessary to control the positive potential impressed on the grid at the beginning of the titration lest the needle of galvanometer will kick off. The agreement between the calculated and found values is very good in each case.