Thermodynamic properties of liquid (cadmium + lead)

Abstract

Measurements of the vapour pressure of cadmium above {(1− x )Pb + x Cd}(1) have given activities of Cd over a large range of composition and of temperature. The results show that the partial molar excess enthalpy and partial molar excess entropy of Cd can be regarded as independent of the temperature. The value of the partial molar excess enthalpy of Cd in pure Pb(l) was also measured by calorimetry: H E (Cd, x → 0) = (9636±170) J mol −1 . All the results, associated with a precise study of solidification equilibria, permitted representation of the thermodynamic properties of Cd and Pb with the help of Margules developments, as functions of x , reliable from solidification to 1000 K: H E ( C d ) / J m o l − 1 = ( 1 − x ) 2 ( 9540 − 2280 x + 40777 x 2 − 86580 x 3 + 76530 x 4 ) , H E ( P b ) / J m o l − 1 = x 2 ( 10680 − 29465 x + 105712 x 2 − 147804 x 3 + 76530 x 4 ) , S E ( C d ) / J K − 1 m o l − 1 = ( 1 − x ) 2 ( 2.280 + 0.722 x + 16.648 x 2 − 52.656 x 3 + 55.605 x 4 ) , S E ( P b ) / J K − 1 m o l − 1 = x 2 ( 1.919 − 10.377 x + 56.140 x 2 − 97.140 x 3 + 55.605 x 4 ) . These expressions serve as evidence for a strong tendency to unmix, the limiting temperature of one-phase stability being very nearly the eutectic temperature.