AbstractAn experimental reinvestigation of the high‐temperature phase equilibria and critical curve of the water‐argon system was made for water mole fractionsxbetween 0.2 and 0.95 in the temperature range from 480 to 663 K and at pressures from 10 to 340 MPa. Molar volumes were measured at thepTx‐phase equilibrium surface. Contrary to the results of an earlier determination [3], the critical curve shows a temperature minimum at 637 K and 84 MPa and proceeds to 658 K at 261 MPa. Thus the curve belongs to the “type II”‐group. Phase equilibrium data are shown for pressures to 300 MPa. A calculation based on a rational equation of state confirms the cri