The phase diagram for the ternary system K2Cr2O7 + KNO3 + H2O was determined at four temperatures, (10, 20, 30, and 40)degrees C. In addition, the densities of the saturated aqueous solutions were measured. The experimental results show that, in the temperature range (10 to 40)degrees C, only potassium nitrate and potassium dichromate were present as solid phases and that the solubility of KNO3 was almost independent of the K2Cr2O7 concentration, whereas the solubility of K2Cr2O7 decreased sharply with increases in the concentration of KNO3.