It is very easy to extract alumina from cliker in the laboratory, but not easy in commercial scale. The reasons why as follows;
(I) Substantial part of alumina and soda once dissolved will be gradually reprecipitated and carried into red mud, when the solution is long in contact with the red mud.
(II) Red mud, sometimes, increases its bulk so muck as to be difficult to be seperated from the solution.
In this paper, experiments and discussions will be described concerning to the mechanisms of the first difficulty above mentioned.