Phase equilibria in the lead-copper (Pb-Cu) liquid system

The shape of the liquid-liquid coexistence curve of the Pb-Cu system with a miscibility gap has been determined by the gamma-ray attenuation technique . According to the authors' measurements, the coordinates of the critical p oint are T-C = 1253.7 +/- 1.5 K, X-C = 37.2 +/- 0.3 at. % Pb. The critical exponent beta of the coexistence curve equals 0.315 +/- 0.005, which agrees closely with the nonclassical value. Near the critical point the values (X -1 + X-2)/2 (X-1 and X-2 are the concentrations of the phases in equilibriu m with each other) exhibit a departure from the law of the rectilinear diam eter.