This is a process for the production of Alumina, which was patented by Karl Josef Bayer in Austria in 1888. It involves the digestion of crushed Bauxite in sodium Hydroxide solution at high temperatures (~240 oC).

Most of the Alumina will dissolve, leaving a "red mud", which is removed by filtration.

The remaining product is then decomposed by reversing the reaction, by cooling and adding the trihydrate, Al2O3.3H2O. This gives:-

2NaAlO2 + 2H2O -> 2NaOH + Al2O3.3H2O

This is then heated to drive off the water of crystallization, which produces Alumina.

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