V-51 NMR studies on the chemical equilibria of vanadium(5+) species were made for aqueous solutions of low ionic strength and pH values ranging from 2.0 to 12.0. The average charge per V atom of these ionic species is from +1 to -2, and the measurements were made at temperatures of 0, 25, and 50 degrees C. Analysis of these results gave accurate thermochemical values for the following major constituent ions of these solutions : VO2+, H2VO4-, HVO42-, H2V2O72-, HV2O73-, V2O74-, V4O124-, and HV10O285-.