THE SOLUBILITY OF ZNO AND ZNAL2O4 IN CRYOLITE MELTS

The solubilities of ZnO and ZnAl2O4 in cryolite-alumina melts at 1020 degrees C have been measured. ZnAl2O4 is the stable solid phase at Al2 O3 contents greater than 1.45 +/- 0.2 wt pet. The results can be repre sented (in terms of wt pet Zn in solution and in the range 1.2 to 13.6 pet Al2O3) by log (pet Zn) = 0.491 + 1.90 log (pet Al2O3) where (pet Al2O3) includes the alumina formed by the dissolution reaction. The re sults are discussed in terms of the variation of the activity of alumi na with its concentration and are consistent with the dissolution mech anism: 3ZnO + 2AlF(3) = 3ZnF(2) + Al2O3 The activity coefficient of Zn F2 in dilute solution with respect to a pure liquid standard state is 0.14.