Abstract: The predominance diagram of dissolved species and potential -pH diagrams of V-H2O system were studied at 25 ℃ by concentration comparison method. The concentration of dissolved species, the borderlines for liquid phases or solid phases, and the borderlines between solid and liquid phase were calculated using the computer programming on the basis of thermodynamic analysis and electrochemistry analysis. The solid regions and liquid regions of kinds of species were ascertained. The predominance diagram of dissolved species and two potential-pH diagrams (at total concentration of V: cT(V)=1.0×10-5 and cT(V)=1.0×10-7 mol·L-1, respectively) of the V-H2O system were plotted. The results showed that under a certain temperature and pressure, the phase stable regions were determined by the total concentration of the species. The stable region of solution was enlarged along with the decreasing of cT(V), whereas the regions of solid phases were reduced.

Key words: V-H2O system, Potential-pHdiagrams, Concentration comparison method, Predominance diagrams