Abstract
The solubilities of ZnO and ZnAl2O4 in cryolite-alumina melts at 1020 °C have been measured. ZnAl2O4 is the stable solid phase at Al2O3 contents greater than 1.45±0.2 wt pct. The results can be represented (in terms of wt pct Zn in solution and in the range 1.2 to 13.6 pct Al2O3) by $$\log (pct Zn) = 0.491 + 1.90\log (pct Al_2 O_3 )$$ where (pct Al2O3) includes the alumina formed by the dissolution reaction. The results are discussed in terms of the variation of the activity of alumina with its concentration and are consistent with the dissolution mechanism: $$3ZnO + 2A1F_3 = 3ZnF_2 + A1_2 O_3 $$ The activity coefficient of ZnF2 in dilute solution with respect to a pure liquid standard state is 0.14.
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