Activity Calculation in Binary System containing Compounds from Standard Heat of Formation of Compounds Chang Yun,Li Wenchao,Zhu Yunkai … Abstract According to the method of activity calculation in binary system containing compounds from standard entropy of formation of compou- nds(il,further using the standard heat of fo rmationof compounds,we deduced the new formula which was also for the compound system. The new formula is △H°f.Ng diny=-RTNN)dT-dinNa (1) here AHg is standard heat of formation of compounds;x,y.is stoichi- ametric factors of the component A,B respectively;NaNa is mole fra- ction of the components A.B respectively;YA.Yn is activity coefficient of components A,B at liquidus temperature. In the binary system Au-B,the activity values calculated by our fo- mula and by Chou's formula are compared with the measured values. They were very well in agreement on the values. In this paper the values of the binary system Al-La is calculated using our new formula.The results are discussed briefly. 79， ， 一 ， ， ， 下罕 人 一 △ “ ， “ 一 一 △ ， ， ， 丫 丫 ， 一 ， 一 犷 ， 一